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Register a new userHiggs to $tautau$ analysis in the future $e^{+}e^{-}$ Higgs factories
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The Circular Electron Positron Collider and International Linear Collider are two electron positron Higgs factories. They are designed to operate at center-of-mass energy of 240 and 250 GeV and accumulate 5.6 and 2 $ab^{-1}$ of integrated luminosity. Using CEPC official samples, the signal strength for Higgs to $tautau$ events are analyzed. The combined accuracy of the signal strength for $Hrightarrow tautau$ at CEPC achieves 0.8%. Extrapolating this analysis to the ILC setup, we conclude the ILC can reach a relative accuracy of 1.1% or 1.2%, corresponding to two benchmark settings of the beam polarization.
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The lepton identification is essential for the physics programs at high-energy frontier, especially for the precise measurement of the Higgs boson. For this purpose, a Toolkit for Multivariate Data Analysis (TMVA) based lepton identification (LICH) has been developed for detectors using high granularity calorimeters. Using the conceptual detector geometry for the Circular Electron-Positron Collider (CEPC) and single charged particle samples with energy larger than 2 GeV, LICH identifies electrons/muons with efficiencies higher than 99.5% and controls the mis-identification rate of hadron to muons/electrons to better than 1%/0.5%. Reducing the calorimeter granularity by 1-2 orders of magnitude, the lepton identification performance is stable for particles with E > 2 GeV. Applied to fully simulated eeH/$mumu$H events, the lepton identification performance is consistent with the single particle case: the efficiency of identifying all the high energy leptons in an event, is 95.5-98.5%.
For the search for additional Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses in the Higgs sector a precise knowledge of their production properties is mandatory. We review the evaluation of the cross sections for the neutral Higgs boson production in association with a photon at future $e^+e^-$ colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production mechanism $e^+e^- to h_i gamma$ ($i = 1,2,3$). The dependence of the lightest Higgs-boson production cross sections on the relevant cMSSM parameters is analyzed numerically. We find relatively small numerical depedences of the production cross sections on the underlying parameters.
This paper presents a full simulation study of the measurement of the production cross section ($sigma_{mathrm{ZH}}$) of the Higgsstrahlung process $mathrm{e^{+}e^{-}rightarrow ZH}$ and the Higgs boson mass ($M_{mathrm{H}}$) at the International Linear Collider (ILC), using events in which a Higgs boson recoils against a Z boson decaying into a pair of muons or electrons. The analysis is carried out for three center-of-mass energies $sqrt{s}$ = 250, 350, and 500 GeV, and two beam polarizations $mathrm{e_{L}^{-}e_{R}^{+}}$ and $mathrm{e_{R}^{-}e_{L}^{+}}$, for which the polarizations of $mathrm{e^{-}}$ and $mathrm{e^{+}}$ are $left(Pmathrm{e^{-}},Pmathrm{e^{+}}right)$ =($-$80%, +30%) and (+80%, $-$30%), respectively. Assuming an integrated luminosity of 250 $mathrm{fb^{-1}}$ for each beam polarization at $sqrt{s}$ = 250 GeV, where the best lepton momentum resolution is obtainable, $sigma_{mathrm{ZH}}$ and $M_{mathrm{H}}$ can be determined with a precision of 2.5% and 37 MeV for $mathrm{e_{L}^{-}e_{R}^{+}}$ and 2.9% and 41 MeV for $mathrm{e_{R}^{-}e_{L}^{+}}$, respectively. Regarding a 20 year ILC physics program, the expected precisions for the $mathrm{HZZ}$ coupling and $M_{mathrm{H}}$ are estimated to be 0.4% and 14 MeV, respectively. The event selection is designed to optimize the precisions of $sigma_{mathrm{ZH}}$ and $M_{mathrm{H}}$ while minimizing the bias on the measured $sigma_{mathrm{ZH}}$ due to discrepancy in signal efficiencies among Higgs decay modes. For the first time, model independence has been demonstrated to a sub-percent level for the $sigma_{mathrm{ZH}}$ measurement at each of the three center-of-mass energies. The results presented show the impact of center-of-mass energy and beam polarization on the evaluated precisons and serve as a benchmark for the planning of the ILC run scenario.
We investigate the possibility of detecting the Higgs bosons predicted in the Minimal Supersymmetric extension of the Standard Model $(h^0, H^0, A^0, H^pm)$, with the reactions $e^{+}e^{-}to bbar b h^0 (H^0, A^0)$, and $e^+e^-to tau^-bar u_tau H^+, tau^+ u_tau H^-$, using the helicity formalism. We analyze the region of parameter space $(m_{A^0}-tanbeta)$ where $h^0, H^0, A^0$ and $H^pm$ could be detected in the limit when $tanbeta$ is large. The numerical computation is done considering two stages of a possible Next Linear $e^{+}e^{-}$ Collider: the first with $sqrt{s}=500$ $GeV$ and design luminosity 50 $fb^{-1}$, and the second with $sqrt{s}=1$ $TeV$ and luminosity 100-200 $fb^{-1}$.
In this work, we study the implication of Higgs precision measurements at future Higgs factories on the MSSM parameter space, focusing on the dominant stop sector contributions. We perform a multi-variable fit to both the signal strength for various Higgs decay channels at Higgs factories and the Higgs mass. The chi-square fit results show sensitivity to mA, tan beta, stop mass parameter mSUSY as well as the stop left-right mixing parameter Xt. We also study the impact of the Higgs mass prediction on the MSSM and compare the sensitivities of different Higgs factories.
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