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Register a new userEvaluation of measurement accuracy of $h to tau ^+ tau ^-$ branching ratio at the ILC with $sqrt{s} = 250$ GeV and 500 GeV
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We evaluate the measurement accuracy of the branching ratio of $h to tau ^+ tau ^-$ at $sqrt{s} = 250$ GeV and 500 GeV at the ILC with the ILD detector simulation. For the $sqrt{s} = 250$ GeV, we assume the Higgs mass of $M_h = 120$ GeV, branching ratio of $mathrm{Br}(h to tau ^+ tau ^-) = 8.0 %$, beam polarization of $P(e^-, e^+) = (-0.8, +0.3)$, and integrated luminosity of $int L dt = 250 mathrm{fb ^{-1}}$. The Higgs-strahlung process $e^+ e^- to Zh$ with $Z to e^+ e^-$, $Z to mu ^+ mu ^-$, $Z to qbar{q}$ mode are analyzed. The measurement accuracy is calculated to be $Delta (sigma cdot mathrm{Br}) / (sigma cdot mathrm{Br}) = 3.5 %$. The scaled result to $M_h = 125$ GeV is estimated to be $4.2 %$. For the $sqrt{s} = 500$ GeV, we assume the Higgs mass of $M_h = 125$ GeV, branching ratio of $mathrm{Br}(h to tau ^+ tau ^-) = 6.32 %$, beam polarization of $P(e^-, e^+) = (-0.8, +0.3)$, and integrated luminosity of $int L dt = 500 mathrm{fb ^{-1}}$. The Higgs-strahlung process $e^+ e^- to Zh$ with $Z to qbar{q}$ mode and $WW$-fusion process $e^+ e^- to u_e bar{ u_e} h$ are analyzed. The measurement accuracy is calculated to be $Delta (sigma cdot mathrm{Br}) / (sigma cdot mathrm{Br}) = 5.7 %$ for Higgs-strahlung with $Z to qbar{q}$ and $7.5 %$ for $WW$-fusion.
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We evaluate the expected measurement accuracy of the branching ratio of the Standard Model Higgs boson decaying into tau lepton pairs $h to tau ^+ tau ^-$ at the ILC with a center-of-mass energy of $sqrt{s} = 500$ GeV with a full simulation of the ILD detector. We assume a Higgs mass of $M_h = 125$ GeV, a branching ratio of $mathrm{BR}(h to tau ^+ tau ^-) = 6.32 %$, beam polarizations of $P(e^+, e^-) = (-0.8,+0.3)$, and an integrated luminosity of $int L dt = 500 mathrm{fb^{-1}}$. The Higgs-strahlung process $e^+ e^- to Zh$ with $Z to q overline{q}$ and the $WW$-fusion process $e^+ e^- to u overline{ u} h$ are expected to be the most sensitive channels at $sqrt{s} = 500$ GeV. Using a multivariate analysis technique, we estimate the expected relative measurement accuracy of the branching ratio $Delta(sigma cdot mathrm{BR}) / (sigma cdot mathrm{BR})$ to be 4.7% and 7.4% for the $q overline{q} h$ and $ u overline{ u} h$ final states, respectively. The results are cross-checked using a cut-based analysis.
The process $e^- e^+ to tau^- tau^+$ is of particular interest because the tau lepton polarisation can be reconstructed, allowing its chiral nature to be probed. This note reports on a study of the reconstruction of the di-tau final state at ILC-500, its selection and the reduction of backgrounds, the identification of the tau leptons decay mode, and on the extraction of the tau leptons polarisation. The performance of this analysis is studied in two models of the ILD detector, one larger (IDR-L) the other smaller (IDR-S), which differ in the outer radius of the TPC and of the subdetectors beyond, and in the magnetic field strength of the detector solenoid. We find that the high-mass tau-pair events in which at least one tau decays haronically can be selected with an efficiency of around 60%, with a remaining background from non-di-tau processes at the few-% level. Single-prong decay modes $tau^pm to pi^pm u, tau^pm to pi^pm pi^0 u, tau^pm to pi^pm pi^0 pi^0 u$ can be correctly identified in around 60-90% of cases, with sample purities in the range 50-90%, depending on decay mode. The sensitivity to tau polarisation was estimated in the four beam polarisation datasets envisaged for the $4 ab^{-1}$ of data forseen for ILC-500. Statistical precisions on the polarisation in the different datasets are predicted to be between 0.5 and 2%. While some small performance differences between the two detector models are seen, they have very similar final sensitivity to the polarisation measurement.
The ILC Technical Design Report documents the design of a 500 GeV linear collider, but does not specify the center-of-mass energy steps of operation for the collider. The ILC Parameters Joint Working Group has studied possible running scenarios, including a realistic estimate of the real time accumulation of integrated luminosity based on ramp-up and upgrade processes, and considered the evolution of the physics outcomes. These physics goals include Higgs precision measurements, top quark measurements and searches for new physics. We present an optimized operating scenario and the anticipated evolution of the precision of the ILC measurements.
Precise measurements of electroweak processes at the International Linear Collider (ILC) will provide unique opportunities to explore new physics beyond the Standard Model. Fermion pair production events are sensitive to new interactions involving a new heavy gauge boson or an electroweak interacting massive particle (EWIMP).We studied the mass reach of new particles at the ILC with $sqrt{s}=250$ GeV by using $e^+ e^-to e^+ e^-$and $e^+ e^-to mu^+ mu^-$ events. We show that a mass reach for BSM particles can be determined with 90% confidence level using a toy Monte Carlo technique.
We study the prospects of measurement of the branching ratio of $h to mu ^+ mu ^-$ at the International Linear Collider (ILC). The study is performed at center-of-mass energies of 250 GeV and 500 GeV, using fully-simulated MC samples with the International Large Detector (ILD) model. For both center-of-mass energies, the two final states $qoverline{q}h$ and $ u overline{ u}h$ have been analyzed. For an integrated luminosity of 2000 fb$^{-1}$ at 250 GeV and 4000 fb$^{-1}$ at 500 GeV, corresponding to the H20 running scenario as well as its staged version, the precision on $sigma times mathrm{BR}(h to mu ^+ mu ^-)$ is estimated.
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