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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 & note.

reconstructed Z boson mass


ISR Photon tagging efficiency


The exclusion limits plots



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.



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