Page History

Machine Learning Flavor Tagging for Future Higgs Factories

July 2023

M, Meyer

Reconstructing long-lived particles with the ILD

Future e+e− colliders, thanks to their clean environment and triggerless operation, offer a unique opportunity to search for long-lived particles (LLPs) at sub-TeV energies. Considered in this contribution are promissing prospects for LLP searches offered by the International Large Detector (ILD), with a Time Projection Chamber (TPC) as the core of its tracking systems, providing almost continuous tracking. The ILD has been developed as a detector concept for the ILC, however, studies directed towards understanding of ILD performance at other collider concepts are ongoing.

Based on the full detector simulation, we study the possibility of reconstruct- ing decays of both light and heavy LLPs at the ILD. For the heavy, O(100 GeV) LLPs, we consider a challenging scenario with small mass splitting between LLP and the dark matter candidate, resulting in only a very soft displaced track pair in the final state, not pointing to the interaction point. We account for the soft beam-induced background (from measurable e+e− pairs and γγ → hadrons processes), expected to give the dominant background contribution due to a very high cross section, and show the possible means of its reduction. As the opposite extreme scenario we consider the production of light, O(1 GeV) pseudo- scalar LLP, which decays to two highly boosted and almost colinear displaced tracks.

We also present the corresponding results for an alternative ILD design, where the TPC is replaced by a silicon tracker modified from the Compact Linear Collider detector (CLICdet) design.

July 2023

J. Klamka

Estimation of the fluxes in highly granular calorimeters

The calorimeter systems of the detectors near future HET factories must operate in wildly different running conditions: machine backgrounds, dominant cross-sections and luminosities vary by several orders of magnitude as function of the center-or-mass energy. A determination of the expected fluxes in the calorimeters is mandatory to scale the electronics, its power dissipation and data output.
A versatile tool has been designed to build those fluxes from the detailled simualtion: energy, time and occupancy spectra, from which secondary distributions such as power, dynamic ranges in energy and time, and data fluxes can be made for a given hypothesis on the electronics. Preliminary results using this tool will be presented and discussed for the ILD detector.

July 2023

by V. Boudry

Stau searches at future e+e– colliders

The direct pair-production of the tau-lepton superpartner, stau, is one of themost interesting channels to search for SUSY. First of all the stau is with highprobability the lightest of the scalar leptons. Secondly the signature of staupair production signal events is one of the most difficult ones, yielding the'worst' and thus most general scenario for the searches.The most model-independent limits on the stau mass comes from the LEP experiments. Theyexclude a stau with mass below 26.3 GeV for any mixing and any difference between stau andneutralino masses larger than the tau mass.The LHC exclusion reach extends to higher masses for large mass differences, but under strongmodel assumptions.Future electron-positron colliders are ideally suited for stau searches: theywill feature increased luminosity and centre-of-mass energy, and improved accelerator,detector and analysis technologies with respect to previous electron-positron colliders.With respect to  hadron colliders, they will profit from a cleaner environment, from theinitial state being known,  and from trigger-less operation of the detectors.

In this contribution, the prospects for discovering stau-pairproduction at future e+e- Higgs factories and the resulting detectorrequirements will be discussed.For detector-level simulations, the study takes the ILD detector conceptand ILC parameters at 500 GeV as example. It includes all SMbackgrounds, as well as beam induced backgrounds, as overlay-on-physicsand - for the first time - overlay-only events, and considers theworst-case scenario for the stau-mixing. It shows that with the chosenaccelerator and detector conditions, SUSY *will* be discovered if theNLSP mass is up to just a few GeV below the kinematic limit of thecollider.

Based on these results, expectations for other center-of-mass energies,luminosities, beam polarisations, beam background and detectorconditions will derived. Among the detector performance criteria,inparticular the role of the hermeticity of the detector, of the trackingacceptance and of the ability to operate trigger-less will be discussedand put into perspective of the experimental environment expected atdifferent Higgs factories.

July 2023

by María Teresa Núñez Pardo de Vera

Search for dark photons at future e+e–  colliders

In a class of theories, dark matter is explained by postulating the existence of a 'dark sector',which interacts gravitationally with ordinary matter. If this dark sector contains a U(1) symmetry,and a corresponding 'dark' photon ($A_{D}$) , it is natural to expect that this particle with kineticly mixwith the ordinary photon, and hence become a 'portal' through which the dark sector can be studied.The strength of the mixing is given by a mixing parameter $(\epsilon)$. Thissame parameter governs both the production and the decay of the $A_{D}$ back to SMparticles, and for values of  $\epsilon$ not already excluded, the signal would bea quite small, and quite narrow resonance: If $(\epsilon)$ is large enough toyield a detectable signal, its decay width will be smaller than the detector resolution, but so largethat the decay back to SM particles is prompt. For masses of the dark photon above the reach ofBelleII,  future high energy e+e- colliders are ideal for searches for such a signal, due to the
low and well-known backgrounds, and the excellent momentum resolution and equallyexcellent track-finding efficiency of the detectors at such colliders.
This contribution will discuss a study investigating the dependency of the limit on the mixingparameter and the mass of the $A_{D}$ using the $A_{D}\rightarrow\mu^{+}\mu^{-}$ decay mode in
the presence of standard model background, using fully simulated signal and background events inthe ILD detector at the ILC Higgs factory. In addition, a more general discussion about the capabilitiesexpected for generic detectors at e+e- colliders operating at other energies will be given.

July 2023

by M. Berggren

Implementation, performance and physics impact of particle identification at Higgs factories

The particle physics community has concluded that the next collider should be an e+ e- Higgs factory. Such a collider would also enable many other precision measurements, e.g. of the top quark and in the electroweak sector, as well as searches for exotic particles. In the ongoing discussions it has become increasingly clear that particle identification including charged hadron ID is a key feature that enables a number of analyses and improves many. A number of different PID systems - from the simple muon ID to gaseous dE/dx and dN/dx to calorimeter shower shapes and time of flight (and more) - are being envisioned for the proposed future Higgs factory detector concepts, however the choices of technologies, their implementation in detector concepts and their physics impact are open questions under study.

This talk discusses the implementation of and performance measures for different PID technologies and their combination, based on the International Large Detector (ILD) as example of a detector concept optimised for particle-flow reconstruction. An overview of physics applications will be given, with a particular focus on the prospects for measuring the Higgs bosons decay to strange quarks.

May 2023

by U. Einhaus

Impact of NLO QCD on Key Physics Processes at Future Higgs Factories

The majority of Monte-Carlo (MC) simulation campaigns for future Higgs factories has so far been based on the leading-order (LO) matrix elements provided by Whizard 1.95, followed by parton shower and hadronization in Pythia6, using the tune of the OPAL experiment at LEP. In this contributi- on, we test the next-to-leading-order (NLO) mode of Whizard. NLO events are generated by POWHEG matching, with parton shower and hadronization provided by Pythia8. The effect on event shape variables and jet reconstruc- tion will be discussed at hadron-level. After passing the events through the full detector simulation of the International Large Detector concept as an example for a ParticleFlow-optimised detector, the jet energy resolution and typical kinematic quantities are compared between NLO and LO at recon- struction level. A first assessment of which physics prospects of future e+e- should be studied with NLO MC in the future will be given.

31 May 2023

by Zhijie Zhao

Search for dark photons at future e+e- colliders

In a class of theories, dark matter is explained by postulating the existence of a 'dark sector', which interacts gravitationally with ordinary matter. If this dark sector contains a U(1) symmetry, and a corresponding 'dark' photon ($A_{D}$) , it is natural to expect that this particle with kineticly mix with the ordinary photon, and hence become a 'portal' through which the dark sector can be studied.
The strength of the mixing is given by a mixing parameter $(\epsilon)$. This same parameter governs both the production and the decay of the $A_{D}$ back to SM particles, and for values of  $\epsilon$ not already excluded, the signal would be a quite small, and quite narrow resonance: If $(\epsilon)$ is large enough to yield a detectable signal, its decay width will be smaller than the detector resolution, but so large that the decay back to SM particles is prompt. For masses of the dark photon above the reach of BelleII,  future high energy e+e- colliders are ideal for searches for such a signal, due to the low and well-known backgrounds, and the excellent momentum resolution and equally excellent track-finding efficiency of the detectors at such colliders.
This contribution will discuss a study investigating the dependency of the limit on the mixing parameter and the mass of the $A_{D}$ using the $A_{D}\rightarrow\mu^{+}\mu^{-}$ decay mode in the presence of standard model background, using fully simulated signal and background events in the ILD detector at the ILC Higgs factory. In addition, a more general discussion about the capabilities expected for generic detectors at e+e- colliders operating at other energies will be given.

31 May 2023

by M. Berggren

Experimental prospects for indirect BSM searches in $e⁺e⁻\rightarrow q\bar{q}$ ($q=c,b$) processes at Higgs Factories

Future Higgs Factories will allow the precise study of 𝑒⁺𝑒⁻→𝑞𝑞¯ with 𝑞=𝑠,𝑐,𝑏,𝑡 interactions at different energies, from the Z-pole to high energies never reached before.
In this contribution, we will discuss the experimental prospects for the measurement of differential observables in 𝑒⁺𝑒⁻→𝑏𝑏¯ and 𝑒⁺𝑒⁻→𝑐𝑐¯processes at high energies, 250 and 500 GeV, with polarised beams, using full simulation samples and the reconstruction chain from the ILD concept group.
These processes call for superb primary and secondary vertex measurements, a high tracking efficiency to correctly measure the vertex charge and excellent hadron identification capabilities using 𝑑𝐸/𝑑𝑥. This latter aspect will be discussed in detail together with its implementation within the standard flavour tagging tools developed for ILD (LCFIPlus). In addition, prospects associated with potential improvements of the 𝑑𝐸/𝑑𝑥reconstruction using cluster counting techniques will also be discussed. Finally, we will briefly discuss the potential of the discovery of BSM models such as Randall-Sundrum models with warped extra dimensions, profiting from measurements of 𝑏/𝑐 quark-related observables at different beam energies and polarisations.

31 May 2023

submitted by A. Irles, J. Marquez

Probing CPV mixing in the Higgs sector in VBF at 1 TeV ILC

Although the studies of tensor structure of the Higgs boson interactions with vector bosons and fermions at CMS and ATLAS experiments have established that the JPC quantum numbers of the Higgs boson should be 0++, small CP violation in the Higgs sector (i.e.  10% contribution of the CP-odd state) cannot be excluded with the current experimental precision. We review possibility to measure CP violating mixing angle between scalar and pseudoscalar states of the extended Higgs sector, at 1 TeV ILC with ILD detector.

May 2023

I. Bozovic

Development of the time-of-flight particle identification for future Higgs factories

With the emergence of advanced Si sensor technologies such as LGADs, it is now possible to achieve exceptional time measurement precision below 50 ps. As a result, the implementation of time-of-flight (TOF) particle identification for charged hadrons at future 𝑒+𝑒− Higgs factory detectors has gained an increasing attention. Other particle identification techniques require a gaseous tracker with excellent dE/dx (or dN/dx) resolution, or a RICH, which adds additional material in front of the calorimeter.
TOF measurements can be implemented either in the outer layers of the tracker or in the electromagnetic calorimeter, and are thus particularly interesting as a PID method for detector concepts based on all-silicon trackers and optimised for particle-flow reconstruction.
In this presentation, we will explore potential integration scenarios of TOF measurement in a future Higgs factory detector, using the International Large Detector (ILD) as an example. We will focus on the challenges associated with crucial components of TOF particle identification, namely track length reconstruction and TOF measurements. The subsequent discussion will highlight the vital impact of precise track length reconstruction and various TOF measurement techniques, including recently developed machine learning approaches. We will evaluate the performance in terms of kaon-pion and kaon-proton separation as a function of momentum, and discuss potential physics applications.

May 2023

by B. Duder

Reconstruction long-lived particles with the ILD detectors

Future e+e− colliders, thanks to their clean environment and triggerless operation, offer a unique opportunity to search for long-lived particles (LLPs) at sub-TeV energies. Considered in this contribution are promissing prospects for LLP searches offered by the International Large Detector (ILD), with a Time Projection Chamber (TPC) as the core of its tracking systems, providing almost continuous tracking. The ILD has been developed as a detector concept for the ILC, however, studies directed towards understanding of ILD performance at other collider concepts are ongoing.

Based on the full detector simulation, we study the possibility of reconstruct- ing decays of both light and heavy LLPs at the ILD. For the heavy, O(100 GeV) LLPs, we consider a challenging scenario with small mass splitting between LLP and the dark matter candidate, resulting in only a very soft displaced track pair in the final state, not pointing to the interaction point. We account for the soft beam-induced background (from measurable e+e− pairs and γγ → hadrons processes), expected to give the dominant background contribution due to a very high cross section, and show the possible means of its reduction. As the opposite extreme scenario we consider the production of light, O(1 GeV) pseudo- scalar LLP, which decays to two highly boosted and almost colinear displaced tracks.

We also present the corresponding results for an alternative ILD design, where the TPC is replaced by a silicon tracker modified from the Compact Linear Collider detector (CLICdet) design.

May 2023

by Jan Klamka

stau searches at e+e- colliders

The future electron-positron colliders offer excellent facilities for SUSYsearches. With respect to previous e+e- colliders, they increase the luminosityand centre-of-mass energy and improve the technologies, while, withrespect to hadron colliders, they offer a cleaner environment, a knowninitial state and a triggerless operation of the detectors.
Moreover, in contrast to hadron colliders, they are very well adapted to thecolour neutral SUSY sector, one of the most relevant for SUSY and explanationof the main problemas of the Standard Model and expected, for theoreticalreasons and from results of the global fits, to have sufficiently light massto be observable at these colliders.
Among the colourless SUSY particles, the superpartner of the tau-lepton,the stau, is one of the most interesting ones in SUSY searches.
The stau is likely to be the lightest of the sfermions, so the first SUSYparticle that could be observed, and it can, for good reasons, be regardedas the  worst and thus most general scenario for the searches: If one canfind the stau, then any alternative next-to-lightest SUSY  particle (NLSP)
will also be findable.
In this contribution, a detailed study of the direct stau pair-production atthe International Linear Collider (ILC) has been performed, showing thecapability of this collider for determining stau exclusion/discovery limitsin a model-independent way.
The studies were done using the full detector simulation and reconstructionprocedures of the International Large Detector concept (ILD) at the ILC. Thesimulation included all SM backgrounds, as well as the beam induced ones.
A detailed study of the effect of beam induced backgrounds, asoverlay-on-physics and - for the first time - overlay-only events, in the staulimits was performed. The analysis of the worst mixing for stau searches atthe ILC conditions is also included.
We are confident that this analysis confirms that at a linear e+e- collider,SUSY *will* be discovered if the NLSP mass is up to just a few GeV belowthe kinematic limit of the collider.

May 2023

by María Teresa Núñez Pardo de Vera

Prospects for exotic light scalar measurements at the e+e- Higgs factory

The physics program of the Higgs factory will focus on measurements of the 125 GeV Higgs boson, with the Higgs-strahlung process being the dominant production channel at 250 GeV. However, production of extra light scalars is still not excluded by the existing experimental data, provided their coupling to the gauge bosons is sufficiently suppressed. Fermion couplings of such a scalar could also be very different from the SM predictions leading to non-standard decay paterns. Considered in the presented study is the sensitivity of future Higgs factory experiments to direct observation of the new light scalar production for the scalar mass range from 50 GeV to 120 GeV.

May 2023

by A.F. Zarnecki

The International Large Detector (ILD) for a future electron-positron collider: Status and Plans

The International Large Detector (ILD) is a detector designed primarily for the International Linear Collider (ILC), a high-luminosity linear electron-positron collider with an initial center-of-mass energy of 250 GeV, extendable to 1 TeV.
The ILD concept is based on particle flow for overall event reconstruction, which requires outstanding detector capabilities including superb tracking, very precise detection of secondary vertices and high-granularity calorimetry. In the past years ILD has been working with building and testing technological prototypes of the key sub-detector technologies, scalable to the full ILD size, studying their integration into a coherent detector, benchmarking the ILD performance and preparing for an optimization of the overall ILD size and costing. The current status has been made public in the ILD Interim Design Report (IDR, 2020) of interest for any future e+e– collider detector. A particular strength of the ILD concept is the integration of a well developed concept for a detector, based on well understood prototypes, with a well-developed and available suite of simulation and reconstruction tools, which allow detailed and reliable studies to be performed. ILD as a general purpose detector optimized for high precision science at an e+e- collider can also serve as an excellent basis to compare the science reach and detector challenges for different collider options. ILD is actively exploring possible synergies with other Higgs/ EW factory options. In this talk we will report on the state of the ILD detector concept, report on recent results and discuss selected examples of studies of an ILD detector at other colliders than ILC.

May 30, 2023

by K. Kawagoe (PSB chair)

A Particle Identification Framework for Linear Colliders

The particle physics community has concluded that the next collider should be an e+e− Higgs factory. Such a collider would also enable many other precision measurements, e.g. of the top quark and in the electroweak sector, as well as searches for exotic particles. In the ongoing discussions it has become increasingly clear that particle identification including charged hadron ID is a key feature that enables a number of analyses and improves many. A number of different PID systems - from the simple muon ID to gaseous dE/dx and dN/dx to calorimeter shower shapes and time of flight (and more) - are being envisioned for the proposed future Higgs factory detector concepts. It is desirable to assess their impact and the effect of combining them in a common tool to enable fair comparisons.

This talk presents a new modular approach to a generic PID framework for the different possible future Higgs factories, embedded in the Key4HEP framework. It discusses implementation questions, performance measures and possible physics applications, exampling the International Large Detector (ILD) concept for the International Linear Collider (ILC).

March 2023

by U. EInhaus

An overview of the International Large Detector (ILD) for a future electron-positron collider

The International Large Detector (ILD) is a detector designed primarily for the International Linear Collider (ILC), a high-luminosity linear electron-positron collider with an initial center-of-mass energy of 250 GeV, extendable to 1 TeV.

The ILD concept is based on particle flow for overall event reconstruction, which requires outstanding detector capabilities including superb tracking, very precise detection of secondary vertices and high-granularity calorimetry. In the past years ILD has focused on building and testing technological prototypes of the key sub-detector technologies, scalable to the full ILD size, studying their integration into a coherent detector, benchmarking the ILD performance and preparing for an optimization of the overall ILD size and costing. The current status has been made public in the ILD Interim Design Report (IDR, 2020) of interest for any future e+e– collider detector. A particular strength of the ILD concept is the integration of a well developed concept for a detector, based on well understood prototypes, with a well-developed and available suite of simulation and reconstruction tools, which allow detailed and reliable studies to be performed.

ILD as a general purpose detector optimized for high precision science at a e+e- collider can also serve as an excellent basis to compare the science reach and detector challenges for different collider options. ILD is actively exploring possible synergies with other Higgs/ EW factory options.

In this talk we will report on the state of the ILD detector concept, report on recent results and discuss selected examples of studies of an ILD detector at other colliders than ILC.

March 31

by T.Behnke

Search for dark photons at future e+e- colliders

In a class of theories, dark matter is explained by postulating the existence of a 'dark sector', which interacts gravitationally with ordinary matter. If this dark sector contains a U(1) symmetry, and a corresponding 'dark' photon ($A_{D}$) , it is natural to expect that this particle with kineticly mix with the ordinary photon, and hence become a 'portal' through which the dark sector can be studied. The strength of the mixing is given by a mixing parameter $(\epsilon)$. This  same parameter governs both the production and the decay of the $A_{D}$ back to SM particles, and for values of  $\epsilon$ not already excluded, the signal would be a quite small, and quite narrow resonance: If $(\epsilon)$ is large enough to
yield a detectable signal, its decay width will be smaller than the detector resolution, but so large that the decay back to SM particles is prompt. For masses of the dark photon above the reach of Belle II,  future high energy e+e- colliders are ideal for searches for such a signal, due to the low and well-known backgrounds, and the excellent momentum resolution and equally excellent track-finding efficiency of the detectors at such colliders. This contribution will discuss a study investigating the dependency of the limit on the mixing parameter and the mass of the $A_{D}$ using the $A_{D}\rightarrow\mu^{+}\mu^{-}$ decay mode in the presence of standard model background, using fully simulated signal and background events in the ILD detector at the ILC Higgs factory. In addition, a more general discussion about the capabilities expected for generic detectors at e+e- colliders operating at other energies will be given.

March 29

by M. Berggren

Background studies in ILD

I will summarize more and less recent studies of machine-related backgrounds in the context of the ILD concept.

March 29

by D. Jeans

Measuring tau polarisation at the ILC

Two fermion production at the International Linear Collider (ILC) allows sensitive searches for new physics, such as heavy gauge bosons Z′. Combining the ILC's polarized beams with measurement of the tau lepton polarization allow detailed probes of the chirality of new interactions beyond the Standard Model.

The tau polarization can be extracted by measuring the distribution of tau decay products. In this study, we have developed a new method which uses the impact parameter of tau decay products to fully reconstruct the tau leptons, including the invisible neutrino momentum, while being insensitive to the possible emission of unseen ISR. This allows optimal reconstruction of the tau spin orientation in order to best measure the polarization.

March 29

by K. Yumino, D. Jeans

RH neutrino pair-production at ILC

We study the search for Right Handed Neutrinos (RHN) at ILC. RHN are introduced by several extensions of the SM to explain the tiny neutrino mass. If RHN is a Majorana particle, RHN pair production is allowed in e−e+ collisions. We focus on RHN pair production based on a minimal U(1)B−L model. A distinctive signature is a pair of same sign leptons, a smoking-gun for Lepton Number Violation. This same sign lepton final state is almost free of SM backgrounds.

In our study we use full detector simulation to analyze RHN production at ILC. We generated the signal process, investigated its properties, developed reconstruction and selection strategies and evaluate the sensitivity at ILC, considering full SM backgrounds. We derive exclusion limits on minimal U(1)B−L parameters at ILC.

March 28

by J. Nakajima, D. Jeans

Probing CPV mixing in the Higgs sector at an e+e- collider at around 1 TeV center-of-mass energy

March 10, 2023

submitted by N. Vukašinović, I.Božović Jelisavčić, G. Kačarević

Stau searches at the ILC

The colour neutral sector is the one most relevant for the suggestions SUSY presents to the problems of the the SM - the hierarchy problem, naturalness, dark matter, the muon g-2 enigma. This sector is both for theoretical reasons, and from the results of global fits, expected to be light. But, unfortunately, it is also the sector for which current energy frontier colliders, viz. the LHC, is less well adapted.

In contrast, any future high energy electron-positron collider offers an excellent facility for SUSY searches in general, and for searches in the colour neutral sector in particular.

Among the particles in this part of the SUSY spectrum, the superpartner of the tau-lepton, the stau, plays an important role. The stau is likely to be the lightest of the sfermions, so to be the first SUSY particle that could be observed. As a benchmark for the power of SUSY searches, the stau is the prime candidate, as it can for good reasons be regarded as the  worst and thus most general scenario for the searches: If one can find the stau, then any alternative next-to-lightest SUSY  particle (NLSP) will also be findable.

In this contribution, a detailed study of the direct stau pair-production at the International Linear Collider (ILC) has been performed, showing the capability of this collider for determining stau exclusion/discovery limits in a model-independent way.

The studies were done using the full detector simulation and reconstruction procedures of the International Large Detector concept (ILD) at the ILC. The simulation included all SM backgrounds, as well as the beam induced ones. A detailed study of the effect of beam induced backgrounds, as overlay-on-physics and - for the first time - overlay-only events, in the stau limits was performed. The analysis of the worst mixing for stau searches at the ILC conditions is also included.

We have thus carefully evaluated all possible complications, both theoretically and experimentally, and are confident that this analysis indeed confirms the statement that at a linear e+e- collider, SUSY *will* be discovered if the NLSP mass is up to just a few GeV below the kinematic limit of the collider.

March 10, 2023

submitted by María Teresa Núñez Pardo de Vera, Jenny List, Mikael Bergen

Experimental prospects for indirect BSM searches in  $e^{-}e^{+}\rightarrow q\bar{q}$, $q=c,b$ processes at high energies

Future Higgs Factories will allow the precise study of $e^{-}e^{+}\rightarrow q\bar{q}$ with $q=s,c,b,t$ interactions at different energies, from the Z-pole up to high energies never reached before.
In this contribution, we will discuss the experimental prospects for the measurement of differential observables in $e^{-}e^{+}\rightarrow b\bar{b}$ and $e^{-}e^{+}\rightarrow c\bar{c}$ processes at high energies, 250 and 500 GeV, using full simulation samples and the full reconstruction chain from the ILD concept group.
These processes call for superb primary and secondary vertex measurements,  a high tracking efficiency to correctly measure the vertex charge and excellent hadron identification capabilities using $dE/dx$.  This latter aspect will be discussed in detail together with its implementation within the standard flavour tagging tools developped for ILD (LCFIPlus). In addition, prospects associated to potential improvements of the $dE/dx$ reconstruction using cluster counting techniques will be also discussed. Finally, we will briefly discuss the potential of discovery of BSM models such as Randall-Sundrum models with warped extra dimensions, profiting from measurements of b/c quark related observables at different beam energies and polarisations.

Highly Granular Calorimeters - Impact of different Higgs Factory Options

Calorimeters optimised for particle flow feature a high segmentation in both longitudinal and transversal direction. The tendency for future Higgs factories is an increase of the beam collision frequency compared to the case of the International Linear Collider (Bunch trains with a repetition rate of 5-10 Hz). For example at circular e+e- colliders as the FCCee the envisaged bunch distance is around 35ns at the Z pole and around 1us for HZ-running. The continuous beam will not allow for the application of power pulsing.
On top an improved timing resolution will yield an increase of the power consumption of the front-end electronics. In addition, the compactness of the readout electronics must remain at the same level as today while being able to cope with significantly increased data fluxes. The R&D for power and space economic solutions for the front-end electronics has to be carried in close coordination with the R&D on cooling systems that may become unavoidable in case of high collision frequencies. A full system study has to include the optimal number of layers and cell sizes that allow for keeping cooling needs at an acceptable level. The integration of cooling systems will likely compromise the acceptance of the detector. The impact on the physics performance will have to be evaluated.  Processes that are particularly affected by a lack of acceptance would be events with missing energy such as invisible Higgs decays. The actual data rate will also depend on the corresponding cross-sections and angular distributions of the relevant physics processes. This may allow for different designs in different angular regions.

March 15, 2023

abstract prepared by R. Poeschl

Reconstruction of long-lived particles with the ILD detector at the ILC

In recent years, long-lived particles (LLPs) have been widely considered in a variety of Beyond the Standard Model (BSM) scenarios and in many different experimental searches for new particles. Future 𝑒+𝑒− colliders, thanks to their clean environment and triggerless operation, offer a unique opportunity to search for such states at sub-TeV energies. Considered in this contribution are promising prospects for LLP searches offered by the International Large Detector (ILD) at the International Linear Collider (ILC), with a Time Projection Chamber (TPC) as the core of its tracking systems, providing almost continuous tracking.

Based on the full detector simulation, we study the possibility of reconstructing decays of heavy LLP at the ILD. We consider a challenging scenario with low mass splitting between LLP and the dark matter candidate, resulting in only a very soft displaced track pair in the final state, not pointing to the interaction point. We consider the soft beam-induced background (from measurable 𝑒+𝑒− pairs and 𝛾𝛾→ hadrons processes), expected to give the dominant background contribution due to a very high cross section, and show the possible means of its reduction. We also present corresponding results for an alternative ILD design, where the TPC is replaced by a silicon tracker modified from the design presented for the Compact Linear Collider detector (CLICdet).

March 8, 2023

Speaker candidate: J. Klamka

Very forward calorimeters at ILC/ILD

Detectors at future e+e- colliders need special calorimeters in the very forward region for a fast estimate of instantaneous and precise measurement of the integrated luminosity. In ILD detector concept, two such calorimeters are foreseen, LumiCal and BeamCal. Both are designed as sandwich calorimeters with very thin sensor planes to keep the Molière radius small, facilitating measurement of the high-energy electron showers. Silicon sensor prototypes and dedicated FE ASICs have been developed and produced matching the timing and dynamic range requirements. The status of the calorimeter prototype performance in the recent beam tests at DESY will be presented, against the expected performance obtained from simulation.

The International Large Detector: Calorimeter system

The International Large Detector (ILD) is a detector designed primarily for the International Linear Collider (ILC), a high-luminosity linear electron-positron collider with an initial center-of-mass energy of 250 GeV, extendable to 1 TeV. This poster will present the current design of its calorimeter system; a highly granular calorimeter in an overall design philosophy called particle flow, developed for optimal global event reconstruction. Open options and critical aspects, as well as prospects for enhanced capabilities in the future will also be presented.

The International Large Detector: Tracking system

The International Large Detector (ILD) is a detector designed primarily for the International Linear Collider (ILC), a high-luminosity linear electron-positron collider with an initial center-of-mass energy of 250 GeV, extendable to 1 TeV. This poster will present the current design of its tracking system; a precision vertex detector positioned very close to the interaction point is followed by a hybrid tracking layout, realized as a combination of silicon tracking with a time projection chamber. Open options and critical aspects, as well as prospects for enhanced capabilities in the future will also be presented.

An overview of the International Large Detector (ILD) for a future electron-positron collider

The International Large Detector (ILD) is a detector designed primarily for the International Linear Collider (ILC), a high-luminosity linear electron-positron collider with an initial center-of-mass energy of 250 GeV, extendable to 1 TeV.
The ILD concept is based on particle flow for overall event reconstruction, which requests outstanding detector capabilities including superb tracking, very precise detection of secondary vertices and high-granularity calorimetry. In the past years the design has focused on building sub-detector technological prototypes scalable to the full ILD size, studying their integration into a coherent detector, benchmarking the ILD performance and preparing for an optimization of the overall ILD size and costing. The current status has been made public in an ILD Interim Design Report (IDR, 2020) of interest for any future e+e– collider detector. The poster will summarize the main IDR results.
Recently, the ILD group has been considering widening its activities to explore synergies with studies at other Higgs factories. A new strategy of the ILD group currently under discussion may also be presented.

From strange to top: activities of the Top/QCD/HF physics group of ILD

The process ee->qq with qq=ss,cc,bb,tt plays a central role in the physics programs of high energy electron-positron colliders operating from the O(100GeV) to O(1TeV) center of mass energies. Furthermore, polarised beams as available at the International Linear Collider (ILC) are an essential input for the complete measurement of the helicity amplitudes that govern the production cross section. Quarks, specially the heaviers, are likely messengers to new physics and at the same time they are ideal benchmark processes for detector optimisation. All four processes call for superb primary and secondary vertex measurements, a high tracking efficiency to correctly measure the vertex charge and excellent hadron identification capabilities. Strange, charm and bottom production are already available below the ttbar threshold.
This contribution will cover the most relevant and latest activities of the ILD concept group on physics studies related to heavy quarks, using detailed simulation and realistic analysis tools
to determine the full potential of ILC on this area. Some of the topics to be discussed will be the top-quark mass measurements, top and less heavy quarks electroweak couplings or BSM searches at ILC with the ILD.

New physics searches with the ILD detector at the ILC

Although the LHC experiments have searched for and excluded many proposed new particles up to masses close to 1 TeV, there are many scenarios that are difficult to address at a hadron collider. This poster gives an overview of recent ILD studies on new particle searches at the ILC. The cases discussed include the light Higgsino, the stau lepton in the coannihilation region relevant to dark matter, and heavy vector bosons coupling to the s-channel in e+e− annihilation.

Higgs physics studies with ILC

With technically mature design and well understood physics program, ILC is a realistic option for realization of a Higgs factory. With a unique physics reach of a linear collider, ILC will significantly complement projections for HL-LHC. Energy staged data collection, employment of beam polarization and capability to reach a TeV center-of-mass energy enable unique precision measurements of various Higgs couplings including its self-coupling. These precision measurements will allow to probe BSM indirectly beyond the reach of direct search at the LHC. This talk will address the simulation studies based on the ILD detector concept for the Higgs physics program at the ILC.

Impact of Advances in Detector Techniques on Higgs Measurements at Future Higgs Factories

At the latest European strategy update in 2020 it has been highlighted that the next highest-priority collider should be an e+e− Higgs factory with a strong focus on precision physics. To utilise the clean event environments, a new generation of collider detector technolgies is being developed along with novel algorithms to push event reconstruction to its full potential.
This talk reviews key Higgs physics measurements and discusses in how far their prospects would benefit from advances in high-level reconstruction and improved detector capabilities. For instance the selection of Higgs and double-Higgs production modes, like ZH vs. ZZ/WW and ZHH vs. ZZH, in fully hadronic decay channels does not only profit from the excellent jet energy resolution of particle flow but also from a full kinematic fit reconstruction. This not only uses the known centre-of-mass energy at lepton colliders, but also allows to take into account invisible jet constituents. Second-generation decays of the Higgs boson are rare, suffer from a huge background at the LHC and are difficult to tag. Novel approaches to particle identification and in particular reconstruction of charged kaons and other strange hadrons substantially enhance charm- and strange-tagging, enabling among others a drastic improvement on the limit of the strange-Yukawa coupling.

Development of the time-of-flight particle identification for future Higgs factories

At the latest European strategy update in 2020 it has been highlighted that the next highest-priority collider should be an e+e− Higgs factory with a strong focus on precision physics. Particle identification will be an essential tool for such precision measurements to utilise clean event environment and push event reconstruction to its full potential. A recent development of the fast-timing Si sensors such as LGADs with a time resolution below 50 ps will allow to enhance precision measurements at the future Higgs factories with an additional separation of π±, K±, p using time-of-flight technique. In this study we present our latest developments of the time-of-flight particle identification algorithm with a brief overview of its potential physics applications, discuss its realistic design implementations inside the future Higgs factory detector using International Large Detector (ILD) as an example and highlight a key role and importance of the fast-timing detectors for π±, K±, p identification.

Measurement of ALR using radiative return at ILC 250 #690

For the electroweak precision study, left-right asymmetry in the total rate for Z boson production (ALR) is important since it can provide a very useful constraint for new physics as well as for operators in the Standard Model (SM) Effective Field Theory, which provides a mathematical framework to express the deviation from the SM by a set of higher dimensional operators model independently. It turned out that the precision of the ALR measurement done at SLC, being at around 1%, is not good enough for the global fit. It is hence motivated to improve this observable at the ILC. Complementary to the method at Z-pole, at the ILC250 we can use the radiative return process, 𝑒+𝑒−→𝛾𝑍, to measure ALR. We will report the full detector simulation based on the International Large Detector (ILD), which is a detector concept for the ILC, for the ALR measurement including estimation of systematic errors.

Stau searches and measurements with the ILD concept at the International Linear Collider #393

The direct pair-production of the tau-lepton superpartner, stau, is one of the most interesting channels to search for SUSY. First of all the stau is with high probability the lightest of the scalar leptons. Secondly the signature of stau pair production signal events is one of the most difficult ones, yielding to the 'worst' and so most global scenario for the searches. The current model-independent stau limits comes from analysis performed at LEP but they suffer from the low energy of this facility. The LHC exclusion reach extends to higher masses for large mass differences, but under strong model assumptions.
The ILC, a future electron-positron collider with energy up to 1 TeV, is ideally suited for SUSY searches. The capability of the ILC for determining exclusion/discovery limits for the stau in a model-independent way is shown in this contribution, together with an overview of the current state-of-the-art. A detailed study of the 'worst' scenario for stau exclusion/discovery, taking into account the effect of the stau mixing on stau production cross-section and efficiency is presented. For selected benchmarks, the prospect for measuring masses and polarised cross-sections will be shown. The studies were done studying events passed through the full detector simulation and reconstruction procedures of the International Large Detector concept (ILD) at the ILC. The simulation included all SM backgrounds, as well as the machine induced ones.

Quark production in high energy electron positron collisions: from strange to top #338

The process ee->qq with qq=ss,cc,bb,tt plays a central role in the physics programs of high energy electron-positron colliders operating from the O(100GeV) to O(1TeV) center of mass energies. Furthermore, polarised beams as available at the International Linear Collider (ILC) are an essential input for the complete measurement of the helicity amplitudes that govern the production cross section. Quarks, specially the heaviers, are likely messengers to new physics and at the same time they are ideal benchmark processes for detector optimisation. All four processes call for superb primary and secondary vertex measurements, a high tracking efficiency to correctly measure the vertex charge and excellent hadron identification capabilities. Strange, charm and bottom production are already available below the ttbar threshold. We will show with detailed detector simulations of the International Large Detector (ILD) that production rate and the forward backward asymmetries of the the different processes can be measured at the 0.1% - 0.5% level and how systematic errors can be controlled to reach this level of accuracy. The importance of operating at different center of mass energies and the discovery potential in terms of Randall-Sundrum models with warped extra dimensions will be outlined.

Strange quark as a probe for new physics in the Higgs sector #337

One of the most interesting yet-to-be answered questions in Particle Physics is the nature of the Higgs Yukawa couplings and their universality. Key information in our understanding of this question arises from studying the coupling of the Higgs boson to second generation quarks. Some puzzles in the flavor sector and potential additional sources of CP violation could also have their origins in an extended Higgs sector.
Rare Higgs decay modes to charm or strange quarks are very challenging or nearly impossible to detect with the current experiments at the Large Hadron Collider, where the large multi-jet backgrounds inhibits the study of light quark couplings with inclusive H->qqbar decays. Future e+e- machines are thus the perfect avenue to pursue this research.
Studies were initiated in the context of Snowmass2021 (https://arxiv.org/abs/2203.07535) with particular emphasis on the Higgs coupling to strange quarks and the related flavour tagging challenges.

This gave light to the development of a novel algorithm for tagging jets originating from the hadronisation of strange quarks (strange-tagging) and the first application of such a strange-tagger to a direct Higgs to strange (h->ssbar) analysis.

The analysis is performed with the future International Large Detector (ILD) at the International Linear Collider (ILC), but it is easily applicable to other Higgs factories. The 𝑃(𝑒−,𝑒+)=(−80%,+30%) polarisation scenario was used for this preliminary result, corresponding to \unit[900]{\ifb} of the initial proposed \unit[2000]{\ifb} of data which will be collected by ILD during its first 10~years of data taking at \sqrts = \unit[250]{GeV}. The study includes as well a preliminary investigation of a Ring Imaging Cerenkov system (RICH) capable of maximising strange-tagging performance in future Higgs factory detectors.

submitted by PSB on 25 Mar 2022

Strange quark as a probe for new physics in the Higgs sector

One of the most interesting yet-to-be answered questions in Particle Physics is the nature of the Higgs Yukawa couplings and their universality. Key information in our understanding of this question arises from studying the coupling of the Higgs boson to second generation quarks. Some puzzles in the flavor sector and potential additional sources of CP violation could also have their origins in an extended Higgs sector.
Rare Higgs decay modes to charm or strange quarks are very challenging or nearly impossible to detect with the current experiments at the Large Hadron Collider, where the large multi-jet backgrounds inhibits the study of light quark couplings with inclusive H->qqbar decays. Future e+e- machines are thus the perfect avenue to pursue this research.
Studies were initiated in the context of Snowmass2021 (https://indico.slac.stanford.edu/event/6617/contributions/1442/attachments/682/1976/SNOWMASS21-EF1_EF2-IF3_IF0_Valentina_Maria_Martina_Cairo-047.pdf) with particular emphasis on the Higgs coupling to strange quarks and the related flavour tagging challenges.

This gave light to the development of a novel algorithm for tagging jets originating from the hadronisation of strange quarks (strange-tagging) and the first application of such a strange-tagger to a direct Higgs to strange (h->ssbar) analysis. The analysis is performed with the initial hypothetical 2ab-1 of data which will be collected by the International Large Detector at the International Linear Collider during its first 10 years of data taking at sqrt(s) = 250GeV, but it is easily applicable to other Higgs factories. The study includes as well a preliminary investigation of a Ring Imaging Cerenkov system (RICH) capable of maximising strange-tagging performance in future Higgs factory detectors.

Measurement of sigma(e+e- -< HZ) x Br(H → ZZ*) at the 250 GeV ILC

We report on studies of the Higgsstrahlung process with the subsequent decay of the Higgs boson to ZZ, where four different final state signatures from ZZ decays are considered. The analysis is performed using Monte Carlo data samples obtained with full detector simulation and polarized beams at the center-of-mass energy of 250 GeV. Overall statistical uncertainty of 5.3% indicates that the Higgs width can be measured using this method with about the same accuracy in the model-independent approach.

15 Sep, 2021

For track:
Future experiments and facilities

Quark production in high energy electron positron collisions: from strange to top #157

The process ee->qq with qq=ss,cc,bb,tt plays a central role in the physics programs of high energy electron-positron colliders operating from the O(100GeV) to O(1TeV) center of mass energies. Furthermore, polarised beams as available at the International Linear Collider (ILC) are an essential input for the complete measurement of the helicity amplitudes that govern the production cross section. Quarks, specially the heaviers, are likely messengers to new physics and at the same time they are ideal benchmark processes for detector optimisation. All four processes call for superb primary and secondary vertex measurements, a high tracking efficiency to correctly measure the vertex charge and excellent hadron identification capabilities. Strange, charm and bottom production are already available below the ttbar threshold. We will show with detailed detector simulations of the International Large Detector (ILD) that production rate and the forward backward asymmetries of the the different processes can be measured at the 0.1% - 0.5% level and how systematic errors can be controlled to reach this level of accuracy. The importance of operating at different center of mass energies and the discovery potential in terms of Randall-Sundrum models with warped extra dimensions will be outlined.

15 Sep, 2021

For track:
Flavor

New physics searches with the ILD detector at the ILC # 130

Although the LHC experiments have searched for and excluded many proposed new particles up to masses close to 1 TeV, there are many scenarios that are difficult to address at a hadron collider. This talk will review a number of these scenarios and present the expectations for searches at an electron-positron collider such as the International Linear Collider. The cases discussed include the light Higgsino, the stau lepton in the coannihilation region relevant to dark matter, and heavy vector bosons coupling to the s-channel in e+e- annihilation. The studies are based on the ILD concept at the ILC.

14 Sep, 2021

For track:
Beyond the Standard Model

Prospects for stau searches and measurements at the ILC #129

The direct pair-production of the tau-lepton superpartner, stau, is one of the most interesting channels to search for SUSY. First of all the stau is with high probability the lightest of the scalar leptons. Secondly the signature of stau pair production signal events is one of the most difficult ones, yielding to the 'worst' and so most global scenario for the searches. The current model-independent stau limits come from analysis performed at LEP but they suffer from the low energy of this facility. The LHC exclusion reach extends to higher masses for large mass differences, but under strong model assumptions.

The ILC, a future electron-positron collider with energy up to 1 TeV, is a promising scenario for SUSY searches. The capability of the ILC for determining exclusion/discovery limits for the stau in a model-independent way is shown in this contribution, together with an overview of the current state-of-the-art. A detailed study of the 'worst' scenario for stau exclusion/discovery taking into account the effect of the stau mixing on stau production cross-section and efficiency is presented. For selected benchmarks, the prospect for measuring masses and polarised cross-sections will be shown. The studies were done using the sgv fast simulation adapted to the ILD detector concept at the ILC.

14 Sep, 2021

For track:
Beyond the Standard Model

Heavy Neutrinos at Future Linear e+e- Colliders

Neutrinos are probably the most mysterious particles of the Standard Model. The mass hierarchy and oscillations, as well as the nature of their antiparticles, are currently being studied in experiments around the world. Moreover, in many models of the New Physics, baryon asymmetry or dark matter density in the universe are explained by introducing new species of neutrinos. Among others, heavy neutrinos of the Dirac or Majorana nature were proposed to solve problems persistent in the Standard Model. Such neutrinos with masses above the EW scale could be produced at future linear e+e- colliders, like the Compact LInear Collider (CLIC) or the International Linear Collider (ILC).

We studied the possibility of observing production and decays of heavy neutrinos in qql final state at the ILC running at 500 GeV and 1 TeV and the CLIC running at 3 TeV. The analysis is based on the WHIZARD event generation and fast simulation of the detector response with DELPHES. Dirac and Majorana neutrinos with masses from 200 GeV to 3.2 TeV are considered. Estimated limits on the production cross sections and on the neutrino-lepton coupling are compared with the current limits coming from the LHC running at 13 TeV, as well as the expected future limits from hadron colliders. Impact of the gamma-induced backgrounds on the experimental sensitivity is also discussed. Obtained results are stricter than other limit estimates published so far.

Track: Neutrino Physics

submitted by Krzysztof Mekala,

This abstract is based on studies by ILD+CLICdp

A (Poster)

Dark matter searches with mono-photon signature at future e+e- colliders

In this contribution, recent results on the sensitivity of future lepton colliders to WIMP dark matter (DM) pair production is reviewed. Considered are processes with mono-photon signature, when DM production is accompanied by a hard photon emission from the initial state radiation, through which the process can be identified.

Corresponding study was performed with full detector simulation for the International Large Detector (ILD) concept at the International Linear Collider (ILC), for a centre-of-mass energy of 500 GeV. In the effective field theory (EFT) approach scales of up to 3 TeV can be tested for different operator types and DM masses almost up to half the collision energy. The sensitivity benefits from the polarised beams, which can reduce the main SM background from neutrino pair production substantially. Systematic uncertainties are also significantly reduced when combining data with different polarisation configurations.

Similar study was performed to investigate potential for detecting DM at the Compact Linear Collider (CLIC) running at 3 TeV. When considering the ratio of the mono-photon energy distributions for left-handed and right-handed polarised electron beams, most systematic uncertainties cancel out, resulting in the best limits on the DM pair-production cross section. These limits can be then translated, using simplified DM models, into exclusion limits for DM and mediator masses for fixed values of the mediator couplings to SM and DM particles.

Pair-production of DM particles at the ILC and CLIC experiments was also studied for scenarios with small mediator masses and small mediator couplings to the SM particles. Limits on the production cross section can be extracted from the two-dimensional distributions of the reconstructed mono-photon events. Limits on the mediator coupling to
electrons are presented for a wide range of mediator masses and widths. For mediator masses up to the centre-of-mass energy of the collider, limits expected from the mono-photon analysis are more stringent  than the limits from direct resonance search in SM decay channels.

Track: Dark matter

submitted by A.F. Zarnecki

This abstract is based on studies by ILD+CLICdp

R

28 April, 2021, #399

Track: Detector R&D and Data Handling

28 April, 2021, #400

Track: Detector R&D and Data Handling

28 April, 2021, #398

Track: Searches for New Physics

Jet energy calibration using e+e- →γZ process at the ILC

The International Large Detector (ILD) is a detector concept for the International Linear Collider (ILC). ILD is a general purpose detector designed to fully reconstruct almost all events. A particular emphasis has been put on excellent jet energy resolution (JER), by optimizing the detector for efficient particle flow reconstruction. Excellent understanding of the absolute jet energy scale (JES) is needed to fully profit from excellent JER. We have developed a data-driven method to extract the absolute JES using the e+e- -> γZ process. This method makes use of measured jet masses and jet and photon directions to extract jet energies without reference to the directly measured energies. Comparing the extracted and directly measured jet energies will allow a very precise control of the JES. We present the result of a full-simulation demonstration of this new method, including an evaluation of the achievable JES accuracy and its dependence on jet energy, direction and flavor.

28 April, 2021, #397

Track: Detector R&D and Data Handling

Author: Takahiro Mizuno

A combined fit to the Higgs Branching Ratios at ILD

We introduce here a new method to measure the Higgs decay branching ratios at future e⁺e⁻ Higgs factories, by directly exploiting class numeration. Given the clean environment at a lepton collider, we build an event sample highly enriched in Higgs bosons and essentially unbiased for any decay mode. The sample can be partitioned into categories using event properties linked to the expected Higgs decay modes. The counts per category are used to fit the Higgs branching ratios in a model independent way. The result of the fit is directly the set of branching ratios, independent from any measurement of a Higgs production mode. Special care is given to an appropriate treatment of the statistical uncertainties. In this contribution, the current status of our implementation of this analysis within the ILD concept detector is presented.

28 April, 2021, #402

Track: Higgs Physics

Authors: Vincent Boudry, Jean-Claude Brient, Fabricio Jimenz, Jonas Kunath

Prospects for the measurement of the $b$-quark mass at the ILC

This talk presents an analysis of the potential of future high-energy electron-positron colliders to measure the $b$-quark mass.  We perform a full-simulation study of the measurement of the ratio of the three-jet rates in events with $b\bar{b}(g)$ and $q\bar{q}(g)$ production, $R_{3}^{bl}$,  and assess the dominant uncertainties, including theory and experimental systematic uncertainties. We find that the ILC "Higgs factory" stage, with an integrated luminosity of 2~\iab at $\sqrt{s}=$ 250~\gev can measure the \bquark \MSbar mass at a scale of 250~\gev ($m_b(250~\gev)$) with a precision of 1~\gev. From this result we extrapolate the potential of the GigaZ run running at $\sqrt{s}= m_Z$. We expect $m_b(m_Z)$ can be determined with an 0.12~\gev{} uncertainty, exceeding the precision of the LEP and SLD measurements by a factor $\sim$3.

28 April, 2021, #403

Track: Top quark and electroweak physics

Track: Flavour Physics and CP Violation

Authors: Juan Fuster, Adrian Irles, Germán Rodrigo, Seidai Tairafune, Marcel Vos, HitoshiYamamoto, Ryo Yonamine

ILD, a Detector for the International Linear Collider

The International Large Detector (ILD) is a detector designed primarily for the International Linear Collider (ILC), a high-luminosity linear electron-positron collider with an initial center-of-mass energy of 250 GeV, extendable to 1 TeV. The ILD concept is based on particle flow for overall event reconstruction, which requests outstanding detector capabilities including superb tracking, very precise detection of secondary vertices and high-granularity calorimetry. In the past years the design has focused on building subdectector technological prototypes scalable to the full ILD size, studying their integration into a coherent detector, benchmarking the ILD performance and preparing for an optimization of the overall ILD size and costing. The current status has recently been made public in an ILD Interim Design Report (IDR) of interest for any future e+e- collider detector. The presentation will summarize the main IDR results and the plans to prepare a technical proposal for the ILC.

ILD, a Detector for the International Linear Collider

The International Large Detector (ILD) is a detector designed primarily for the International Linear Collider (ILC), a high-luminosity linear electron-positron collider with an initial center-of-mass energy of 250 GeV, extendable to 1 TeV. The ILD concept is based on particle flow for overall event reconstruction, which requests outstanding detector capabilities including superb tracking, very precise detection of secondary vertices and high-granularity calorimetry. In the past years the ILD design has focused on building subdectector technological prototypes scalable to the full ILD size, studying their integration into a coherent detector, benchmarking the ILD performance and preparing for an optimization of the overall ILD size and costing. The current status has recently been made public in an ILD Interim Design Report (IDR) of interest for any future e+e- collider detector. The presentation will summarize the main IDR results and the plans to prepare a technical proposal for a detector at the ILC, should ILC move forward.

Track 13. Detectors for Future Facilities (incl. HL-LHC), R&D, Novel Techniques

Abstract #766

Heavy quark production in high energy electron positron collisions

The process ee->qq with qq=cc,bb,tt plays a central role in the physics programs of high energy electron-positron colliders. Polarised beams as available at the international collider ILC are an essential input for the complete measurement of the helicity amplitudes that govern the production cross section. Heavy quarks are likely messengers to new physics and at the same time they are ideal benchmark processes for detector optimisation. All three processes call for superb primary and secondary vertex measurements and a high tracking efficiency to correctly measure the vertex charge. Charm and bottom production are already available below the ttbar threshold. The program must be completed by the measurement of electroweak ttbar production. We will show with detailed detector simulations of the ILD Detector that production rate and the forward backward asymmetries of the three processes can be measured at the 0.1% - 0.5% level and how systematic errors can be controlled to reach this level of accuracy. The discovery potential in terms of Randall-Sundrum models with warped extra dimensions will be outlined.

25 Feb 2020

Track 04. Top Quark and Electroweak Physics

Abstract #767

Improving Electroweak Precision Observables Including m_W, Γ_W, A_LR and TGCs with the ILD Detector

We discuss the improvements that the ILC can make in precision electroweak observables based on studies with the ILD detector concept. These include observables from WW production and radiative return to the Z at a centre of mass energy of 250 GeV, and from a dedicated stage of running at the Z pole. These improvements take advantage of the ILC capabilities for polarized electron and positron beams, and an accelerator design that accommodates data-taking at a wide range of beam energies. We also present new results on precision measurements of fermion pair production. The studies include experimental considerations evaluated in the context of the ILD detector concept and discussion of experimental strategies targeted at controlling relevant systematic uncertainties.

25 Feb 2020

Track 04. Top Quark and Electroweak Physics

Abstract #768

ILC as a SUSY discovery and precision instrument.

Data from the LHC at 7, 8, and 13 TeV have so far yielded no evidence for new particles beyond the 125 GeV Higgs boson; in particular, there have been no signs of SUSY. However, the complementary nature of physics with e+e- collisions still offers many interesting scenarios in which SUSY can be discovered at the ILC. These scenarios take advantage of the capability of e+e- collisions to observe events with missing four-momentum - a signature not available at hadron colliders, where only transverse imbalance is observable. Due to low backgrounds and trigger-less operation, detectors at e+e- colliders can observe events with much less visible energy than what is possible at hadron colliders. In this contribution, we will present detailed simulation studies done with the ILD concept at the ILC. These studies include simulation of the full SM background, as well as realistic accelerator conditions. We will show results both on expected discovery and exclusion reaches for the most challenging SUSY channels, such as higgsinos or winos at low mass differences. Evaluations of precision of model-parameter measurements, in case of discovery, will also be given. We also report on how such measurements can be used to put constraints on parts of the sparticle-spectrum beyond direct reach, and to discriminate between different models of SUSY breaking at high scales.

25 Feb 2020

Track 03. Beyond the Standard Model

Abstract #769

The ILD Software Tools and Detector Performance

The ILD detector is a detector concept designed for high precision physics at the ILC. It is optimized for particle flow event reconstruction with extremely precise tracking capabilities and highly granular calorimeters. Over the last decade ILD has developed a suite of sophisticated software components for simulation and reconstruction in the context of the iLCSoft ecosystem in collaboration with other future collider projects. We will present an overview of the ILD software from the detailed and realistic modeling of the detector with DD4hep, over the event reconstruction algorithms with its pattern recognition and particle flow algorithms to the high level reconstruction for flavor tagging and particle identification. Most of the these tools have been developed in a detector agnostic way and are also applicable to other future lepton colliders. Finally we will present an overview of the resulting detector performance that can be achieved with ILD following the ILD Interim Design Report (IDR) that recently has been made public.

25 Feb 2020

Track 14. Computing and Data Handling

Abstract #770

Study of  ΗγZ coupling at the ILC

In the Standard Model, ΗγZ coupling is a loop induced coupling, therefore it might receive relatively large correction from BSM physics. In the SM Effective Field Theory, the measurement of HγZ coupling can provide a very useful constraint that helps the global fit, in particular the precise determination of HZZ and HWW couplings. At the ILC, there are two direct ways to study HγZ coupling: measuring the decay branching ratio of H->γZ, or measuring the production cross section of e+e- -> γH. In this talk, we will introduce the full simulation studies using these two ways, based on the detector model ILD at the ILC. Results will be given for an integrated luminosity of 2 ab-1 at ECM=250 GeV.

Electroweak precision observables for the Higgs Coupling determination at the ILC

Very generically the same BSM physics that modifies Higgs couplings can also modify other electroweak couplings. A concrete example is given about the contact interaction operators in the Standard Model Effective Field Theory. In this respect, the electroweak precision observables (EWPOs) such as A_l (left right asymmetry in electron Z coupling) and Gam_l (partial width of Z to leptons) turn out to be very useful for the Higgs coupling determination. ILC can improve the EWPOs in at least two ways: by radiative return process or by a dedicated Z-pole running (Giga-Z option). In both ways, the beam polarizations play a very important role. This talk will give current prospects of improving the EWPOs at the ILC.

ILD for the International Linear Collider

The International Large Detector (ILD) is a detector concept for the International Linear Collider (ILC), a high-luminosity linear electron-positron collider with an initial center-of-mass energy of 250 GeV (extendable to 1 TeV). The ILD is optimized with the concept of particle flow for overall event reconstruction so that it will deliver excellent performance for high-precision Higgs and top measurements, as well as high-sensitivities for possible new phenomena, utilizing the advantages of an electron-positron collider. Particle flow implies that all particles in an event, charged and neutral, are individually reconstructed. This requirement has a large impact on the design of the detector, and has played a central role in the optimisation of the system. Superb tracking capabilities and outstanding detection of secondary vertices are other important aspects. The overall layout, sub-detector technologies, expected performance, and recent progress of the ILD will be presented.

Probing the dark sector via searches for invisible decays of the Higgs boson at the ILC

To unravel the nature of dark matter is one of the most important goals in particle physics today.
The Higgs field may well be the portal that couples to a whole new dark sector in which the dark matter candidate particle is accommodated. Searches for invisible decays of the Higgs boson, which may originate from the Higgs boson decaying to dark matter directly or via some mediator, would give us a clear signal of new physics.
At e+e- colliders, taking advantage of the recoil mass technique, the 4-momentum of the Higgs boson can be fully reconstructed even though it decays invisibly. A specific advantage of the ILC are the polarized beams which help to suppress the background significantly. We will report our studies based on the full simulation of the ILD detector concept, using the e+e- -> ZH with Z->qq/ll channels. We obtain a sensitivity to BR(H->invisible) of 0.3% (95% C.L. upper limit) at the
ILC 250 GeV with an integrated luminosity of 2 ab-1. We will also discuss the impact of center-of-mass energy, beam spectrum, ISR, and
detector performance for the Higgs to invisible measurement.

Production and electroweak couplings of 3rd generation quarks at the ILC

The 3rd generation quarks are, due to their large mass, highly sensitive probes for new physics connected to the electroweak symmetry breaking. Linear e+e- colliders allow for clean measurements of heavy quark final states between the Z-Pole and the TeV scale with sensitivities to different aspects of the manifestations of new physics in the extracted electroweak couplings. At the same time these processes are ideal benchmarks for the optimisation of detectors at linear colliders. This includes for example the event-by-event distinction between b and anti-b quarks indispensable for the proper measurement of differential observables. The contribution will outline with full simulation studies the capabilities of the ILD concept. An efficiency of 30% has been achieved for the charge measurements in bb final states, which is about a factor three better than presented earlier. We will also present new results using the fully hadronic tt final state. Finally quantitative estimations of the reach in detecting the onset of new physics will be given.

The ILC as a natural SUSY discovery machine and precision microscope: From light higgsinos to tests of unification

The requirement of electroweak naturalness in simple supersymmetric models motivates the existence of a cluster of four light higgsinos with mass 100-300 GeV, the lighter the better. While such light compressed spectra may be challenging to observe at LHC, future e+e- colliders with sqrt(s) > 2m(higgsino) would serve as both a SUSY discovery machine and a precision microscope.
We study higgsino pair production signatures at the ILC based on full, Geant4-based simulation of the ILD detector concept. We examine several benchmark scenarios that may or may not be accessible to HL-LHC searches, with mass di?fferences between the higgsino states between 20 and 4 GeV. Assuming
sqrt(s)=? 500 GeV and 1000 fb^-1 of integrated luminosity, the individual higgsino masses can be measured to 1-2% precision in case of the larger mass diff?erences, and still at the level of 5% for the smallest mass diff?erence case. The higgsino mass splittings are sensitive to the electroweak gaugino masses and can allow extraction of gaugino masses to ? 3 - 20% (depending on the model).
Extrapolation of gaugino masses via renormalization group running can test the hypothesis of gaugino mass uni?cation. We also examine a case with natural generalized mirage mediation where the uni?cation of gaugino masses at an intermediate scale apparently gives rise to a natural SUSY spectrum somewhat beyond the reach of HL-LHC.

Probing the dark sector via searches for invisible decays of the Higgs boson at the ILC

To unravel the nature of dark matter is one of the most important goals in particle physics today.
The Higgs field may well be the portal that couples to a whole new dark sector in which the dark matter candidate particle is accommodated. Searches for invisible decays of the Higgs boson, which may originate from the Higgs boson decaying to dark matter directly or via some mediator, would give us a clear signal of new physics.
At e+e- colliders, taking advantage of the recoil mass technique, the 4-momentum of the Higgs boson can be fully reconstructed even though it decays invisibly. A specific advantage of the ILC are the polarized beams which help to suppress the background significantly. We will report our studies based on the full simulation of the ILD detector concept, using the e+e- -> ZH with Z->qq/ll channels. We obtain a sensitivity to BR(H->invisible) of 0.3% (95% C.L. upper limit) at the
ILC 250 GeV with an integrated luminosity of 2 ab-1. We will also discuss the impact of center-of-mass energy, beam spectrum, ISR, and
detector performance for the Higgs to invisible measurement.

Production and electroweak couplings of 3rd generation quarks at the ILC

The 3rd generation quarks are, due to their large mass, highly sensitive probes for new physics connected to the electroweak symmetry breaking. Linear e+e- colliders allow for clean measurements of heavy quark final states between the Z-Pole and the TeV scale with sensitivities to different aspects of the manifestations of new physics in the extracted electroweak couplings. At the same time these processes are ideal benchmarks for the optimisation of detectors at linear colliders. This includes for example the event-by-event distinction between b and anti-b quarks indispensable for the proper measurement of differential observables. The contribution will outline with full simulation studies the capabilities of the ILD concept. An efficiency of 30% has been achieved for the charge measurements in bb final states, which is about a factor three better than presented earlier. We will also present new results using the fully hadronic tt final state. Finally quantitative estimations of the reach in detecting the onset of new physics will be given.

The ILC as a natural SUSY discovery machine and precision microscope: From light higgsinos to tests of unification

The requirement of electroweak naturalness in simple supersymmetric models motivates the existence of a cluster of four light higgsinos with mass 100-300 GeV, the lighter the better. While such light compressed spectra may be challenging to observe at LHC, future e+e- colliders with sqrt(s) > 2m(higgsino) would serve as both a SUSY discovery machine and a precision microscope.
We study higgsino pair production signatures at the ILC based on full, Geant4-based simulation of the ILD detector concept. We examine several benchmark scenarios that may or may not be accessible to HL-LHC searches, with mass di?fferences between the higgsino states between 20 and 4 GeV. Assuming
sqrt(s)=? 500 GeV and 1000 fb^-1 of integrated luminosity, the individual higgsino masses can be measured to 1-2% precision in case of the larger mass diff?erences, and still at the level of 5% for the smallest mass diff?erence case. The higgsino mass splittings are sensitive to the electroweak gaugino masses and can allow extraction of gaugino masses to ? 3 - 20% (depending on the model).
Extrapolation of gaugino masses via renormalization group running can test the hypothesis of gaugino mass uni?cation. We also examine a case with natural generalized mirage mediation where the uni?cation of gaugino masses at an intermediate scale apparently gives rise to a natural SUSY spectrum somewhat beyond the reach of HL-LHC.

Coupling strength and CP properties in Higgs -> tau tau at ILC

The CP nature of the Higgs and its couplings is imprinted on spin correlations between its decay products. We will present a method based on Higgs decays to tau lepton pairs, showing that the mixing between even and odd CP components can be measured to a precision of 4.3 degrees at ILC-250. We will also show results on the expected measurement precision of the coupling between the Higgs boson and tau lepton at ILC.

Based on 
Eur. Phys. J. C75 (2015) no.12, 617 
Phys.Rev. D98 (2018) no.1, 013007
NIM A810 (2016) 51

Higgs self-coupling projections at the ILC

Higgs self-coupling measurement provides a direct probe of the Higgs potential, which is important both for understanding of electroweak symmetry breaking and for testing of electroweak baryogenesis. In this talk we will present studies addressing two issues about the Higgs self-coupling measurement at the ILC at the center-of-mass energies of 500 GeV and 1 TeV. The first issue is about how model independent determination of the triple Higgs coupling is possible, provided that in a general BSM theory the double Higgs production processes can receive corrections not only from the triple Higgs coupling but also from other Higgs couplings. The second issue is a realistic estimation about the experimental precision on the double Higgs production cross sections, based on the full detector simulation using the ILD and by including all SM background processes. 

The studies for the first issue are published on arXiv:1708.09079, while the paper for the second issue is in preparation.

Sensitivity to anomalous VVH couplings at the ILC

Abstract: deviations in Higgs couplings may not only appear in the strength of SM-like Higgs couplings, but also appear as distinct Lorentz structures, which is manifest in particular in the effective filed theory. In the case of VVH couplings (V=Z, W), one new CP-even and one new CP-odd tensor couplings can be presented as anomalous couplings. Experimental determinations of those anomalous VVH couplings can provide new insights in probing the BSM models and finding new CP violating effects in the Higgs sector. This talk reports the experimental studies of anomalous VVH couplings at the ILC, emphasizing how the effects of each anomalous coupling and SM-like coupling can be distinguished and determined simultaneously by taking advantage of various angular distributions. The results will be given based on the full detector simulation of the ILD and including major Higgs production and decay channels, for both Ecm=250 and 500 GeV at the ILC.

Part of the studies has been published on arXiv:1712.09772, a more comprehensive paper is in preparation.

Prospects of measuring Higgs boson decays into muon pairs at the International Linear Collider

We study the prospects for measuring the branching ratio of h→μ+μ− at the International Linear Collider. The study is performed at center-of-mass energies of 250 GeV and 500 GeV based on full simulation of the International Large Detector. For both center-of-mass energies, the two final states qq⎯⎯⎯h and νν⎯⎯⎯h have been analyzed. For an integrated luminosity of 2 ab−1 at 250 GeV and 4 ab−1 at 500 GeV, the combined precision on the cross section times branching ratio of h→μ+μ− is estimated to be 17.5%. The impact of the transverse momentum resolution on this analysis is also studied. A precision of 15% could be archived with 10 times better resolution, while a precision would increase to 25% with 10 times worse resolution.

Status of tracking detectors at ILC

Precision measurements of the properties of the Higgs boson, discovered by the ATLAS and CMS experiments of the LHC, and the top quark, the heaviest known elementary particle, are among the main physics goals for experiments at the proposed international linear collider (ILC). These measurements must reach an unprecedented level of precision to allow us to decipher the next fundamental layer of physics, called new physics. The vertex and tacking detectors of the ILC experiments will be a key towards accomplishing the ambitious physics programs of the latter. We discuss the design requirements of these state-of-the-art detector systems, driven from the stringent physics and experimental constraints of the ILC.

Study of the Higgs couplings to leptons and Higgs CP properties at the ILC

In the Standard Model the many Yukawa couplings between the Higgs and fermions, responsible for the mass generation for fermions, are predicted to be strictly proportional to the masses of fermions. Any deviation from this prediction would clearly signal new physics beyond the SM. Many alternative ways of introducing Yukawa couplings in BSM models can result in quite different characteristics for different types of fermions, e.g. upper- or down-type, lepton- or quark-type, 3rd-, 2nd- or 1st-generation. More over, if the SM-like Higgs is an admixture of CP even and CP odd states, as preferred in the electroweak baryon genesis models which can potentially explain the baryon number asymmetry in our universe, the Higgs Yukawa couplings will be modified at the tree level. In particular the Higgs to tau tau decay process provides an ideal place for probing the Higgs CP properties. In this talk, we will give the prospects about the measurements of Htautau and Hmumu couplings at the International Linear Collider (ILC), including the Higgs CP phase measurement in Higgs to tautau process using a novel tau reconstruction method. All the simulation studies are performed based on the full detector simulation for the International Large Detector (ILD).

Search for Light Scalars Produced in Association with a Z boson at the 250 GeV stage of the ILC

In many models with extended Higgs sectors, e.g. in Two Higgs Doublet Models, in the NMSSM as well as in Randall Sundrum models, there exists an additional scalar h, which can easily be lighter than the Standard Model (SM) like Higgs. Its coupling to the Z boson is expected to be small if the 125 GeV Higgs boson is SM-like. Such a light scalar with suppressed couplings to the Z boson would have escaped detection at LEP due to its limited luminosity. With a factor of 1000 higher luminosity and polarized beams, the International Linear Collider (ILC) is expected to have substantial discovery potential for such states. Furthermore, searches for additional scalars at LEP and LHC are usually dependent on the model details, such as decay channels. Thus, it is necessary to have a more general analysis with model-independent assumptions.
We present a search for a such a light higgs boson produced in association with Z boson at the ILC with a center-of-mass energy of 250 GeV, using the full Geant4-based simulation of the ILD detector concept. In order to be as model-independent as possible, the analysis is performed using the recoil technique, in particular with the Z boson decaying into a pair of muons. Expected exclusion cross section limits for different higgs masses between 10 and 120 GeV will be given in terms of a scale factor with respect to the Standard Model Higgs-strahlung process cross section.

3rd Generation Quark and Electroweak Boson Couplings at the 250 GeV stage of  the ILC

The 3rd generation quarks are, due to their large mass, highly sensitive probes for new physics connected to the electroweak symmetry breaking. While top quark pair production requires center-of-mass energies of larger than 350 GeV, the first stage of the ILC at a center-of-mass energy of 250 GeV can perform precision measurements of bottom quark pair production, thereby settling the long standing ~3\sigma tension between the LEP experiments and SLD. For this measurement, the polarised beams of the ILC are of special importance as they enable the separation of the vector and axial-vector couplings of the b quark to Z boson and photon. Another important precision probe for new physics are triple gauge boson coupings (TGCs). Thanks to the polarised beams and the much higher luminosity, a significant increase in precision beyond past and present experiments is expected at the first stage of the ILC for the TGCs involving W bosons. For both measurements, we will report recent projections based on detailed simulations of the ILD detector concept, and highlight the role of important detector performance aspects, e.g. for the separation of b and anti-b jets based on vertex charge measurements and particle ID.

Study of the Higgs couplings to leptons and Higgs CP properties at the ILC

In the Standard Model the many Yukawa couplings between the Higgs and fermions, responsible for the mass generation for fermions, are predicted to be strictly proportional to the masses of fermions. Any deviation from this prediction would clearly signal new physics beyond the SM. Many alternative ways of introducing Yukawa couplings in BSM models can result in quite different characteristics for different types of fermions, e.g. upper- or down-type, lepton- or quark-type, 3rd-, 2nd- or 1st-generation. More over, if the SM-like Higgs is an admixture of CP even and CP odd states, as preferred in the electroweak baryon genesis models which can potentially explain the baryon number asymmetry in our universe, the Higgs Yukawa couplings will be modified at the tree level. In particular the Higgs to tau tau decay process provides an ideal place for probing the Higgs CP properties. In this talk, we will give the prospects about the measurements of Htautau and Hmumu couplings at the International Linear Collider (ILC), including the Higgs CP phase measurement in Higgs to tautau process using a novel tau reconstruction method. All the simulation studies are performed based on the full detector simulation for the International Large Detector (ILD).

Search for Light Scalars Produced in Association with a Z boson at the 250 GeV stage of the ILC

In many models with extended Higgs sectors, e.g. in Two Higgs Doublet Models, in the NMSSM as well as in Randall Sundrum models, there exists an additional scalar h, which can easily be lighter than the Standard Model (SM) like Higgs. Its coupling to the Z boson is expected to be small if the 125 GeV Higgs boson is SM-like. Such a light scalar with suppressed couplings to the Z boson would have escaped detection at LEP due to its limited luminosity. With a factor of 1000 higher luminosity and polarized beams, the International Linear Collider (ILC) is expected to have substantial discovery potential for such states. Furthermore, searches for additional scalars at LEP and LHC are usually dependent on the model details, such as decay channels. Thus, it is necessary to have a more general analysis with model-independent assumptions.
We present a search for a such a light higgs boson produced in association with Z boson at the ILC with a center-of-mass energy of 250 GeV, using the full Geant4-based simulation of the ILD detector concept. In order to be as model-independent as possible, the analysis is performed using the recoil technique, in particular with the Z boson decaying into a pair of muons. Expected exclusion cross section limits for different higgs masses between 10 and 120 GeV will be given in terms of a scale factor with respect to the Standard Model Higgs-strahlung process cross section.

3rd Generation Quark and Electroweak Boson Couplings at the 250 GeV stage of  the ILC

The 3rd generation quarks are, due to their large mass, highly sensitive probes for new physics connected to the electroweak symmetry breaking. While top quark pair production requires center-of-mass energies of larger than 350 GeV, the first stage of the ILC at a center-of-mass energy of 250 GeV can perform precision measurements of bottom quark pair production, thereby settling the long standing ~3\sigma tension between the LEP experiments and SLD. For this measurement, the polarised beams of the ILC are of special importance as they enable the separation of the vector and axial-vector couplings of the b quark to Z boson and photon. Another important precision probe for new physics are triple gauge boson coupings (TGCs). Thanks to the polarised beams and the much higher luminosity, a significant increase in precision beyond past and present experiments is expected at the first stage of the ILC for the TGCs involving W bosons. For both measurements, we will report recent projections based on detailed simulations of the ILD detector concept, and highlight the role of important detector performance aspects, e.g. for the separation of b and anti-b jets based on vertex charge measurements and particle ID.

ILD for the International Linear Collider

The International Large Detector (ILD) is a detector concept for the International Linear Collider (ILC), a 250-500 GeV (extendable to 1 TeV) center-of-mass high-luminosity linear electron-positron collider. The ILD is optimized with the concept of particle flow for overall event reconstruction so that it will deliver excellent performance for high-precision Higgs and top measurements, as well as high-sensitivities for possible new phenomena, utilizing the advantages of an electron-positron collider. Particle flow implies that all particles in an event, charged and neutral, are individually reconstructed. This requirement has a large impact on the design of the detector, and has played a central role in the optimisation of the system. Superb tracking capabilities and outstanding detection of secondary vertices are other important aspects. The overall layout, sub-detector technologies, expected performance, and recent progress of the ILD will be presented.

Sensitivity to anomalous VVH couplings at the ILC (submitted by Tomohisa Ogawa)

The discovery of the 125 GeV Higgs boson, which was the last missing element of the standard model (SM), provided us the insight that the electroweak symmetry breaking is done by a Higgs condensate in the vacuum, namely the Higgs mechanism. However the SM does not give the dynamics explaining why and how that Higgs condensate is formed. On the other hand, the SM can not provide candidate particles for the dark matter, and can not explain the baryon number asymmetry in our universe, etc. Therefore new physics beyond the SM is needed to answer all of those questions. Remarkably the effects of new physics will be inevitably imprinted in the properties of the Higgs boson, namely its couplings to other SM particles and its CP nature. At the future International Linear Collider (ILC), one of the most important goals is precise measurement those properties.

In this talk, we will focus on the measurement of the general Lorentz structure of couplings between Higgs and vector bosons (VVH, V=Z or W) at the ILC, based on an approach of the effective field theory. The sensitivities to both CP-even and CP-odd dimension-5 operators are evaluated by exploring various Higgs production and decay channels, in particular taking advantage of the sensitivities from differential cross sections measurements. The studies are performed based on full detector simulation of the International Large Detector (ILD), for ECM = 250 GeV and 500 GeV. Combined sensitivities are given for some realistic running scenarios of the ILC.

Prospects for electroweak precision measurements and triple gauge couplings at a staged ILC (submitted by Jenny List)

In absence of a direct discovery of new particles, precision measurements of the properties of known particles will provide the most powerful probe for phenomena beyond the Standard Model. Future electron positron linear colliders with polarised beams, like the International Linear Collider (ILC), will provide a unique laboratory for such measurements, complementary to hadron colliders. In this contribution, we will review in particular the prospects for electroweak precision measurements, like the mass of the W boson, or the weak mixing angle, as well as for measurements of charged triple gauge couplings based simulations of the ILD detector concept for the ILC. In all of these, the exact knowledge of the beam polarisation and the beam energy plays an important role. Therefore we will also discuss the precision determination of these accelerator parameters from collision data. We will pay special tribute to the most recent discussions concerning a possible first stage of the ILC operating at a center-of-mass energy of 250 or 350 GeV, but also comment of the full ILC running plan.

Full simulation study of the process $e^+ e^- \rightarrow b\bar{b}$ at \sqrt(s) = 250 GeV at the ILC (submitted by Roman Pöschl)

The heavy quark doublet plays a central role in the quest for new physics. The complementary between studies of electroweak top quark production and bottom quark production is therefore intuitively clear and pointed out in the literature. Let us remind that the tension between the LEP measurement and the Standard Model prediction of the forward-backward asymmetry $A_{fb}^b$ is still one of the unsolved questions in the field and may be interpreted as a first manifestation of new physics in the heavy quark sector. The process $e^+ e^- \rightarrow b\bar{b}$ at the ILC offers a unique opportunity for a final word on the tension. Polarised beams allow for a large disentangling of the coupling constants or form factors that govern the $\gamma/Z \,b\bar{b}$ vertex.

The contribution will present a detailed simulation study of the process $e^+ e^- \rightarrow b\bar{b}$ at 250\, GeV with the ILD Detector. Besides the phenomenological implications, the contribution will demonstrate that with a careful analysis of the final state the charge of the b-quarks can be determined on an event-by-event basis with the ILD Detector. Such a capability is unprecedented by past and present particle physics experiments.

Naturalness and light Higgsinos: why ILC is the right machine for SUSY discovery (submitted by Jacqueline Yan)

Radiatively-driven natural Supersymmetry, a theoretically and experimentally well-motivated framework, centers around the predicted existence of four  light, nearly mass-degenerate Higgsinos with mass $\sim 100-200$ GeV (not too far above $m_Z$). Their small mass splittings of at most 20 GeV implies very little visible energy of accompanying Standard Model particles decayed from heavier Higgsinos. Given that other SUSY particles are considerably heavy, this makes detection challenging at hadron colliders. On the other hand, the clean environment of an electron-positron collider with  $\sqrt{s}>2m_{Higgsino}$ would enable a decisive search of these required Higgsinos, and thus either the discovery or exclusion of natural SUSY.  We present a detailed simulation study of precision measurements of Higgsino masses and production cross sections at  $\sqrt{s}$ = 500 GeV of the proposed International Linear Collider currently under consideration for construction in Japan. The study is  based on a Geant4 simulation of the International Large Detector concept. We examine several benchmark points  just beyond the HL-LHC reach, with a mass spectrum containing four light Higgsinos directly accessible by the ILC, and the mass differences between the lightest SUSY particle and the heavier states ranging from about 4 to 20 GeV. It can be shown that their masses and production cross sections are able to be precisely measured to approximately 1% precision or better. These precise measurements allow for extracting the underlying weak scale SUSY parameters. The fitted parameters give predictions for the masses of heavier SUSY states, which provide motivation for future high-energy colliders. Additionally, dark matter properties may be derived. Evolution of the measured gaugino masses to high energies should allow one to distinguish the hypothesis of gaugino mass unification from other compelling possibilities such as mirage mediation.

Natural SUSY at the ILC: from MZ to the GUT scale (submitted by Mikael Berggren)

The most basic requirement for naturalness in supersymmetric models is the existence of rather light partners of the Higgs boson, the Higgsinos, at masses not too far above M_Z. Despite the pressure from LHC data on the simplest high-scale models (like the cMSSM), such light Higgsinos can still be realised in different types of GUT-scale models from NUHM2 to mirage unification models. The ILC will offer the unique discovery potential for the elusive higgsino particles and allow for precision measurements of their properties. In this contribution, prospects for the achievable precisions for masses, the very small mass splittings and polarised production cross sections will be presented. Based on these, we studied the possibilities to determine the SUSY parameters at the weak scale, and to extrapolate their running to the GUT scale. We will discuss the prospects to thereby differentiate between various GUT-scale models and SUSY breaking schemes and to predict the masses of the remaining SUSY particles. In particular the latter could provide important guidance for the energy scale of the next hadron collider after the LHC.

Scalar sector at future e+e- colliders (submitted by Ivanka Bozovic-Jelisavcic)

Future e+e- colliders offer excellent possibilities for precision studies in the Higgs sector due to the clean experimental conditions and low backgrounds compared to hadron colliders. At lower energies i.e. below 500 GeV, the Higgstrahlung is the dominant Higgs production mechanism. With the recoil mass analysis technique being the unique feature of e+e- colliders, the Higgstrahlung allows model-independent studies of the Higgs couplings as well as the access to the invisible Higgs decays. If considered simultaneously with WW-fusion dominating Higgs production at higher energies, determination of the Higgs total width is possible at a percent level. Scalar sector searches are reviewed for ILC and CEPC using recent research updates obtained with the fully simulated ILD and CEPC detectors.

ILD for the International Linear Collider (submitted by Kiyotomo Kawagoe)

 The International Large Detector (ILD) is a detector concept for the International Linear Collider (ILC), a 250-500 GeV (extendable to 1 TeV) center-of-mass high-luminosity linear electron-positron collider. The ILD is optimized with the concept of particle flow for overall event reconstruction so that it will deliver excellent performance for high-precision Higgs and top measurements, as well as high-sensitivities for possible new phenomena, utilizing the advantages of an electron-positron collider. Particle flow implies that all particles in an event, charged and neutral, are individually reconstructed. This requirement has a large impact on the design of the detector, and has played a central role in the optimisation of the system. Superb tracking capabilities and outstanding detection of secondary vertices are other important aspects. The overall layout, sub-detector technologies, expected performance, and recent progress of the ILD will be presented.

ILD for the International Linear Collider (submitted by Kiyotomo Kawagoe)

 The International Large Detector (ILD) is a detector concept for the International Linear Collider (ILC), a 250-500 GeV (extendable to 1 TeV) center-of-mass high-luminosity linear electron-positron collider. The ILD is optimized with the concept of particle flow for overall event reconstruction so that it will deliver excellent performance for high-precision Higgs and top measurements, as well as high-sensitivities for possible new phenomena, utilizing the advantages of an electron-positron collider. Particle flow implies that all particles in an event, charged and neutral, are individually reconstructed. This requirement has a large impact on the design of the detector, and has played a central role in the optimisation of the system. Superb tracking capabilities and outstanding detection of secondary vertices are other important aspects. The overall layout, sub-detector technologies, expected performance, and recent progress of the ILD will be presented.