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NumberConferenceTitle/abstractsubmitted onStatus
60ICHEP 2022

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.

submitted by U. EinhausS
59ICHEP 2022

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.

submitted by B. DudarS
58ICHEP 2022

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+𝑒𝛾𝑍, 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.

submitted by PSB on 30 Mar 2022S
57ICHEP 2022

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.

submitted by PSB on 28 Mar 2022S
56ICHEP 2022

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.

submitted by PSB on 25 Mar 2022
55ICHEP 2022

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

S
54DIS2022

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.

submitted by Valentina Cairo and Matthew BassoS
53LP2021

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

Future experiments and facilities

A(poster)
52LP2021

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

Flavor

A(poster)
51LP2021

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

Beyond the Standard Model

A(poster)
50LP2021

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

Beyond the Standard Model

Merged with #130
49EPS-HEP 2021

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)

48EPS-HEP 2021

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

47EPS-HEP 2021Charged Hadron Identification with dE/dx and Time-of-Flight at Future Higgs Factories
The design of detector concepts has been driven since a long time by requirements on transverse momentum, impact parameter and jet energy resolutions, as well as hermeticity. Only rather recently it has been realised that the ability to idenfity different types of charged hadrons, in particular kaons and protons, could have important applications at Higgs factories, ranging from improvements in tracking, vertexing and flavour tagging to measurements requiring strangeness-tagging. While detector concepts with gaseous tracking can exploit the specific energy loss, all-silicon-based detectors have to rely on fast timing layers in front of or in the first layers of their electromagnetic calorimeters. This presentation will review the different options for realising kaon and proton identification, introduce recently developed reconstruction algorithms and present full detector simulation prospects for physics applications using the example of the ILD detector concept.

28 April, 2021, #399

Track: Detector R&D and Data Handling

A (Poster)
46EPS-HEP 2021Kinematic fitting for ParticleFlow Detectors at Future Higgs Factories
Many physics analyses in Higgs, top and electroweak physics improve the  kinematic reconstruction of the final state by constrained fits. This is a particularly powerful tool at $e^+e^-$ colliders, where the initial state four-momentum is known and can be employed to constrain the final state. A crucial ingredient to kinematic fitting is an accurate estimate of the measurement uncertainties, in particular for composed objects like jets. This contribution will show how the particle flow concept, which is a design-driver for most detectors proposed for future Higgs factories, can --- in addition to an excellent jet energy measurement --- provide detailed estimates of the covariance matrices for each individual particle-flow object and each individual jet. Combined with information about leptons and secondary vertices in the jets, the kinematic fit enables to correct $b$- and $c$-jets for missing momentum from neutrinos from semi-leptonic heavy quark decays. The impact on the reconstruction of invariant di-jet masses and the resulting improvement in $ZH$ vs $ZZ$ separation will be presented, using as example the full simulation of the ILD detector concept. As an outlook, the expected benefit for the Higgs self-coupling measurement from double Higgs production will be discussed.

28 April, 2021, #400

Track: Detector R&D and Data Handling

A (Poster)
45EPS-HEP 2021New 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 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.

28 April, 2021, #398

Track: Searches for New Physics

A
44EPS-HEP 2021

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

R
43EPS-HEP 2021

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

A
42EPS-HEP 2021

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

R
41TIPP2021

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.

01 Feb 2021A
40ICHEP

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.

25 Feb 2020

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

Abstract #766

A
39ICHEP

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

A
38ICHEP

Improving Electroweak Precision Observables Including mW, ΓW, ALR 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

A
37ICHEP

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

A
36ICHEP

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

A
35Higgs Couplings 2019, Oxford

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.

23.07.2019A
34Higgs Couplings 2019, Oxford

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.

23.07.2019A
33DPF2019, Boston

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.

09.05.2019A
32Lepton-Photon 2019 Toronto

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.

12.04.2019A (poster)
31Lepton-Photon 2019 Toronto

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.

12.04.2019A (poster)
30Lepton-Photon 2019 Toronto

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.

12.04.2019A (poster)
29EPS-HEP 2019 Ghent

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.

12.04.2019A
28EPS-HEP 2019 Ghent

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.

12.04.2019A
27EPS-HEP 2019 Ghent

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.

12.04.2019A
26Higgs Couplings 2018

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

09.01.2018A
25Higgs Couplings 2018

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.

09.01.2018A
24Higgs Couplings 2018

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.

09.01.2018A
23Higgs Couplings 2018

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

We study the prospects for measuring the branching ratio of hμ+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 qqh and ννh have been analyzed. For an integrated luminosity of 2 ab1 at 250 GeV and 4 ab1 at 500 GeV, the combined precision on the cross section times branching ratio of hμ+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.

09.01.2018A
22VERTEX 2018

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.

08.29.2018 (from ILD and SiD)A
21The Rencontres of Vietnam "Windows on the Universe"

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).

04.06.2018A
20The Rencontres of Vietnam "Windows on the Universe"

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.

04.09.2018Speaker candidates could not be found.
19he Rencontres of Vietnam "Windows on the Universe"

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.

04.10.2018A
18ICHEP 2018

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).

02.27.2018A
17ICHEP 2018

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.

02.27.2018A
16ICHEP 2018

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.

02.27.2018S
157th International Conference on High Energy Physics in the LHC era

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.

11.15.2017Modified to a more general talk on ILC
14CHEF 2017Technical instrumentation R&D for ILD large scale device (V. Balagura for ILD SiW ECAL group, submitted by J.C. Brient)07.14.2017A
13Cooling system R&D and endocarp geometry (D. Grondin for ILD SiW ECAL group, submitted by J.C. Brient)A
12Dead zone analysis of ECAL barrel modules under static and dynamic loads (T. Pierre-Emile for ILD SiW ECAL group, submitted by J.C. Brient)A
11Performance study of SKIROC2/A ASIC for ILD Si-W ECAL (T. Suehara for ILD SiW ECAL group, submitted by J.C. Brient)A
10ECAL device in view of the ILC staging proposal (H. Videau for ILD SiW ECAL group, submitted by J.C. Brient)A
9IEEE NSS/MIC 2017

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

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.

ieee_ILD_v2.pdf
05.08.2017A (poster)
8EPS-HEP 2017

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.

04.13.2017A (changed from poster to oral)
7

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.

04.13.2017A (poster), presenter: Robert Karl
6

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.

04.13.2017A (poster), presenter: Sviatoslav Bilokin
5

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.

03.31.2017A, speaker: Suvi-Leena Lehtinen
4ALPS2017

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.

02.13.2017A
3

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.

02.01.2017A, speaker: Junping Tian
2

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.

01.17.2017R (Our abstract is merged with that of CLICdp for a more general talk.)
1Instrumentation 2017

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.

12.12.2016R (T. Omori gives a more general talk on behalf of LCC: "Status and Future Perspectives of the ILC Project: Accelerator / Detector R&D".)

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