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# Branching ratio H-->mu+mu-

## Short description.

Physics Motivation: measure Higgs Yukawa coupling to muons, which provides useful test for ratio of Yukawa coupling between 2nd/3rd generation leptons (with $//$); between 2nd generation lepton/quark (with $//$).

Search Channel: $//$ with $//$ at $//$ of 500 GeV.

Detector Benchmark: very sensitive to high momentum resolution/tracking efficiency, algorithm for isolated lepton tagging.

Two different works are ongoing or finish in soon.

1. Work using DBD-world samples: explored at $//$ of 250/500 GeV, left-/right-handed beam polarization, two processes of $//$ and $//$
2. Work using IDR-world samples: written in above

## Main observables.

final observable: precision on the cross section times branching ratio $//$, branching ratio of $//$.

intermediate observables: track momentum resolutions, muon pair invariant mass $//$, event-by-event mass resolution $//$ which is calculable using the covariance matrix of momenta space.

## Candidate plots for IDR.

Some comparison between IDR-L and IDR-S in reconstructed particle level has done. More details can be found in my talk on 2019Apr03. All plots are left-handed beam polarization. All histograms are normalized to 1.

Overall distribution after BDTG score cut: $//$ and $//$

Similar plot ("barrel category"); require both muons are in barrel region $//$

Similar plot ("mixed category"); require one muon is in barrel region $//$, and another is in endcap/forward region $// 0.7 //]]>$

Only ~5% events are the case with both muons flying in endcap/forward region.

## Results.

A toy MC technique is applied by using overall $//$ distribution after BDTG score cut to estimate the precision on $//$. Two detector models and two beam polarization cases are considered. In addition, the theoretical number is provided which assumes 100% signal efficiency, no backgrounds, and no detector effects.

IDR-LIDR-STheory
left

$//$

$//$

$//$

right

$//$

$//$

$//$

• My real analysis is about a factor of 3 worse than the theoretical limit. There are several reasons mixed up: imperfection of cuts, existence of irreducible background mainly come from $//$, detector effect, and so on.
• The right-handed case does not provide good precision due to too small number of events, only ~8 events with 1600 fb-1 statistics.
• IDR-L gives relatively ~2.4% better precision than IDR-S, because overall $//$ distribution is better in IDR-L. In detail, IDR-L gives significantly better performance in "barrel category", and similar performance in "mixed category". Almost all events are categorized in these two groups, resulting better result with IDR-L.

## IDR note.

You can see my private overleaf project from here. The contents are only IDR-world.

## People.

Reviewed by Ivanka Bozovic and Filip Zarnecki

## References.

(1) DBD-world references

Branching ratio measurement of $//$ at the ILC [Talk at LCWS2017]

Impact of Momentum Resolution on $//$ Measurement [Talk at ILD Meeting 2018]

Branching ratio measurement of $//$ at the ILC [Talk at ALCW2018]

Prospects of measuring Higgs boson decays into muon pairs at the ILC [Talk at LCWS2018]

Shin-ichi Kawada, Jenny List, Mikael Berggren, "Branching ratio measurement of $//$ at the ILC" (LCWS2017 proceedings) [LINK]

Shin-ichi Kawada, Jenny List, Mikael Berggren, "Prospects of measuring Higgs boson decays into muon pairs at the ILC" (LCWS2018 proceedings) [LINK]

(2) IDR-world references

Talk at Wednesday ILD Analysis/Software Meeting [2018Oct10, 2018Nov21, 2019Jan30, 2019Apr03]

Status Report: $//$ Benchmark [Talk at ILD Benchmarking Days]

Status Report: $//$ Benchmark [Talk at ILD Benchmarking Days II]

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