Abstract
We report on studies of the $e^+e^- \to HZ$ process with the subsequent decay of the Higgs boson $H \to Z Z^\star$, where the $Z Z^\star$ combination is reconstructed in the final states with two jets and two leptons. The analysis is performed using Monte Carlo data samples obtained with detailed ILD detector simulation assuming the integrated luminosity 2 ab$^{-1}$, the beam polarizations ${\cal{P}}_{e^-e^+} = (-0.8, +0.3)$, and the center-of-mass energy $\sqrt{s}$ = 250 GeV. The analysis is also repeated for the case of two 0.9 ab$^{-1}$ data samples with polarizations ${\cal{P}}_{e^-e^+} = (\mp0.8, \pm0.3)$. The process is measured in four decay channels, which correspond to two combinations for the Higgs final states and two decay modes of the directly produced $Z$ boson, $Z \to q \bar{q}$ and $Z \to \nu \bar{\nu}$. To obtain the Higgs boson mass distributions, we used the variables $M(jj\ell\ell)$ and $M_{\Delta} = M(jj\ell\ell) - M(jj) + M(Z_{\rm nom})$, where $M(Z_{\rm nom})$ = 91.2 GeV. Contributions of the potential background processes are taken into account based on the available MC event samples. We propose a model-independent method for obtaining the width of the Higgs boson using the measurement of the $e^+e^- \to HZ$ process.
Highlights
Since the discovery of the Higgs boson by the ATLAS and CMS collaborations [1,2] in 2012, the important task is to measure parameters of this particle with the highest possible accuracy
We propose to use the process eþe− → ZH with the subsequent decay H → ZZ⋆ to measure the product of the cross section and the decay branching fraction, which can theoretically be expressed as: σðeþe− → HZÞ × BrðH → ZZ⋆Þ 1⁄4 C · g4Z=ΓH: ð1Þ
The MCParticles [16] and PandoraPFOs collections are included in the samples
Summary
Since the discovery of the Higgs boson by the ATLAS and CMS collaborations [1,2] in 2012, the important task is to measure parameters of this particle with the highest possible accuracy. The measurement of this product can be used to obtain the width of the Higgs boson with a high accuracy, because the coupling gZ is expected to be determined combining ILC and LHC results with an uncertainty of about 0.5% [9] using other processes. In this analysis we assume the data sample of 2 ab−1 collected by the ILD experiment in the eþe− collisions at a center-ofmass energy 250 GeV. In this paper four channels are studied and the final precision of the Higgs width measurement is calculated combining accuracies obtained in these channels
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