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Short description.

We study the sensitivity of ILD to detect low mass, higgs-like states. This is done with the recoil-technique, ie. we only search for and measure the Z(*) decays into two muons, and  search for peaks in the the recoil-mass spectrum. The actual decay-mode of the Higgs-like object is not important. Many BSM models predict such states, and once the decay-modes and/or the coupling to the Z is significantly different (lower) than the SM-higgs, such a state might well have escaped detection at LEP (and LHC).

This benchmark in particular can probe three features:

  • Muon detection, in particular isolated ones.
  • Muon identification.
  • Detecting, identifying and measuring ISR photons.

Main observables.

The main direct observables for the signal are the momentum and identity of decay-products of the Z, Depending on the mass of the Higgs-like object, the Z might be on-shell or off-shell. Different patterns of "return to the Z" ISR will also emerge depending on the Higgs-like object's mass. The physics observable is the exclusion/discovery range for such states as a function of their mass, and the strength of the coupling to the Z wrt that of the SM higgs - Z coupling.

Optimisation deliverables.

  • Isolated muon detection and identification
  • ISR finding and reconstruction

IDR plots.

reconstructed Z boson mass

2 fermion channel

lepton_pair_inm_2f.C    lepton_pair_inm_difference_2f.C  lepton_pair_inm_sigma_2f.C

M_{S}=20 GeV


lepton_pair_inm_nh_20.C lepton_pair_inm__difference_nh20.C lepton_pair_inm_sigma_nh20.C

ISR Photon tagging efficiency


Recoil mass distribution

The exclusion limits plots


exclusion_limits.C                                                             exclusion_limits_08_03_compare_LEP.C                        exclusion_limits_08_03_compare_py_de.C

IDR note.


Search_Scalars_at_the_ILC.pdf (new version, Nov 18, 2019)


Main investigator: Yan Wang , assisted by Jenny List and Mikael Berggren, reviewed by Kiyotomo Kawagoe and Junping Tian.


The GitHub repository is ILDbench_extraH in the ILDAnaSoft project.



Backup plots, mainly for different scalar masses.

reconstructed Z boson mass

M_{S}=100 GeV

lepton_pair_inm_nh_100.pdf lepton_pair_inm__difference_nh100.pdf lepton_pair_inm_sigma_nh100.pdf

lepton_pair_inm_nh_100.C lepton_pair_inm__difference_nh100.C lepton_pair_inm_sigma_nh100.C

M_{S}=200 GeV

lepton_pair_inm_nh_200.pdf lepton_pair_inm__difference_nh200.pdf lepton_pair_inm_sigma_nh200.pdf

lepton_pair_inm_nh_200.C lepton_pair_inm__difference_nh200.C lepton_pair_inm_sigma_nh200.C

M_{S}=300 GeV

lepton_pair_inm_nh_300.pdf lepton_pair_inm__difference_nh300.pdf lepton_pair_inm_sigma_nh300.pdf

lepton_pair_inm_nh_300.C lepton_pair_inm_difference_nh300.C lepton_pair_inm_sigma_nh300.C

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