Publications (48)169.51 Total impact

Article: Indirect reach of heavy MSSM Higgs bosons by precision measurements at future lepton colliders
[Show abstract] [Hide abstract]
ABSTRACT: In the Minimal Supersymmetric Standard Model (MSSM), the bottom Yukawa coupling of the Higgs boson can considerably deviate from its Standard Model prediction due to nondecoupling effects. We point out that the ratio of the Higgs boson decay branching fraction to a bottom quark pair and that to a $W$boson pair from the same production channel is particularly sensitive to large additional MSSM Higgs boson mass regions at future electronpositron colliders. Based on this precision measurement, we explicitly show the indirect discovery reach of the additional Higgs bosons according to planned programs of the International Linear Collider.  [Show abstract] [Hide abstract]
ABSTRACT: We study direct searches of additional Higgs bosons in multitopquarks events at the LHC RunII, its luminosity upgraded version with 3000 fb$^{1}$, and the International Linear Collider (ILC) with the collision energy of 1 TeV. Additional Higgs bosons are predicted in all kinds of extended Higgs sectors, and their detection at collider experiments is a clear signature of the physics beyond the standard model. We consider two Higgs doublet models with the discrete symmetry as benchmark models. If these additional Higgs bosons are heavy enough, the decay modes including top quarks can be dominant, and the searches in multitopquarks events become an important probe of the Higgs sector. We evaluate the discovery reach in the parameter space of the model, and find that there are parameter regions where the searches at the LHC with 3000 fb$^{1}$ cannot survey, but the searches at the ILC 1 TeV run can. The combination of direct searches at the LHC and the ILC is useful to explore extended Higgs sectors. 
Article: T.
[Show abstract] [Hide abstract]
ABSTRACT: W bosons produced at high transverse momentum in hadron collisions can have polarization along the direction perpendicular to the production plane, which is odd under naïve T reversal where both the threemomenta and angular momenta are reversed. Perturbative QCD predicts nonzero polarization at the oneloop level, which can be measured as parityodd components in the angular distribution of charged leptons from the decay of W bosons. We perform a detectorlevel simulation with the generator MadGraph5_aMC@NLO, and demonstrate that the asymmetry can be observed at the 8 TeV LHC with 20 fb^{1} of data. If confirmed, it will be the first experimental measurement of the sign of the imaginary part of oneloop QCD amplitudes.  [Show abstract] [Hide abstract]
ABSTRACT: In this report, selected topics of tau leptons are collected in view of the highenergy collider experiments and the Higgsboson search. Those topics include decay modes, taujet tagging, collinear approximation and the tau polarization. Using these unique properties of tau leptons, it is possible to observe various properties of the Higgs boson or the associated scalars in the extended Higgs models at the LHC.  [Show abstract] [Hide abstract]
ABSTRACT: W bosons produced at high transverse momentum in hadron collisions can have polarization along the direction perpendicular to the production plane, which is odd under na$\ddot{\i}$veTreversal where both the threemomenta and angular momenta are reversed. Perturbative QCD predicts nonzero polarization at the oneloop level, which can be measured as parityodd components in the angular distribution of charged leptons from the decay of W bosons. We perform a detectorlevel simulation with the generator MadGraph5_aMC@NLO, and demonstrate that the asymmetry can be observed at the 8 TeV LHC with 20 fb$^{1}$ of data. If confirmed, it will be the first experimental measurement of the sign of the imaginary part of oneloop QCD amplitudes.  [Show abstract] [Hide abstract]
ABSTRACT: After the discovery of the standardmodellike Higgs boson at the LHC, the structure of the Higgs sector remains unknown. We discuss how it can be determined by the combination of direct and indirect searches for additional Higgs bosons at future collider experiments. First of all, we evaluate expected excluded regions for the mass of additional neutral Higgs bosons from direct searches at the LHC with the 14 TeV collision energy in the two Higgs doublet models with a softlybroken $Z_2$ symmetry. Second, precision measurements of the Higgs boson couplings at future experiments can be used for the indirect search of extended Higgs sectors if measured coupling constant with the gauge boson slightly deviates from the standard model value. In particular, in the two Higgs doublet model with the softlybroken discrete symmetry, there are four types of Yukawa interactions, so that they can be discriminated by measuring the pattern of deviations in Yukawa coupling constants. Furthermore, we can fingerprint various extended Higgs sectors with future precision data by detecting the pattern of deviations in the coupling constants of the standardmodellike Higgs boson. We demonstrate how the pattern of deviations can be different among various Higgs sectors which predict the electroweak rho parameter to be unity; such as models with additional an isospin singlet, a doublet, triplets or a septet. We conclude that as long as the gauge coupling constant of the Higgs boson slightly differs from the standard model prediction but is enough to be detected at the LHC and its highluminosity run or at the International Linear Collider, we can identify the nonminimal Higgs sector even without direct discovery of additional Higgs bosons at the LHC.  [Show abstract] [Hide abstract]
ABSTRACT: We study the methods and their accuracies for determining tan\beta\ in two Higgs doublet models at future lepton colliders. In addition to the previously proposed methods using direct production of additional Higgs bosons, we propose a method using the precision measurement of the decay branching ratio of the standardmodel (SM)like Higgs boson. The method is available if there is a deviation from the SM in the coupling constants of the Higgs boson with the weak gauge bosons. We find that, depending on the type of Yukawa interactions, this method can give the best sensitivity in a wide range of tan\beta. 
Article: Weight function method for precise determination of top quark mass at Large Hadron Collider
[Show abstract] [Hide abstract]
ABSTRACT: We propose a new method to measure a theoretically welldefined top quark mass at the LHC. This method is based on the "weight function method" proposed in ref. [17]. It requires only lepton energy distribution and is basically independent of the production process of the top quark. We perform a simulation analysis of the top quark mass reconstruction with $t\overline{t}$ pair production and lepton+jets decay channel at the leading order. The estimated statistical error of the top quark mass is about 0.4 GeV with an integrated luminosity of 100 fb$^{1}$ at $\sqrt{s}=14$ TeV. We also estimate some of the major systematic uncertainties and find that they are under good control. 
Article: Weight function method for precise determination of top quark mass at Large Hadron Collider
[Show abstract] [Hide abstract]
ABSTRACT: We propose a new method to measure a theoretically welldefined top quark mass at the LHC. This method is based on the “weight function method,” which we proposed in our preceding paper. It requires only lepton energy distribution and is basically independent of the production process of the top quark. We perform a simulation analysis of the top quark mass reconstruction with pair production and lepton + jets decay channel at the leading order. The estimated statistical error of the top quark mass is about with an integrated luminosity of at . We also estimate some of the major systematic uncertainties and find that they are under good control.  [Show abstract] [Hide abstract]
ABSTRACT: We discuss complementarity of discovery reaches of heavier neutral Higgs bosons and charged Higgs bosons at the LHC and the International Linear Collider (ILC) in two Higgs doublet models (2HDMs). We perform a comprehensive analysis on their production and decay processes for all types of Yukawa interaction under the softlybroken discrete symmetry which is introduced to avoid flavour changing neutral currents, and we investigate parameter spaces of discovering additional Higgs bosons at the ILC beyond the LHC reach. We find that the 500 GeV run of the ILC with the integrated luminosity of 500 fb^{1} shows an advantage for discovering the additional Higgs bosons in the region where the LHC cannot discover them with the integrated luminosity of 300 fb^{1}. For the 1 TeV run of the ILC with the integrated luminosity of 1 ab^{1}, production processes of an additional Higgs boson associated with the top quark can be useful as discovery channels in some parameter spaces where the LHC with the integrated luminosity of 3000 fb^{1} cannot reach. It is emphasized that the complementary study at the LHC and the ILC is useful not only to survey additional Higgs bosons at the TeV scale, but also to discriminate types of Yukawa interaction in the 2HDM.  [Show abstract] [Hide abstract]
ABSTRACT: We discuss complementarity of discovery reaches of heavier neutral Higgs bosons and charged Higgs bosons at the LHC and the International Linear Collider (ILC) in two Higgs doublet models (2HDMs). We perform a comprehensive analysis on their production and decay processes for all types of Yukawa interaction under the softlybroken discrete symmetry which is introduced to avoid flavour changing neutral currents, and we investigate parameter spaces of discovering additional Higgs bosons at the ILC beyond the LHC reach. We find that the 500 GeV run of the ILC with the integrated luminosity of 500 fb^{1} shows an advantage for discovering the additional Higgs bosons in the region where the LHC cannot discover them with the integrated luminosity of 300 fb^{1}. For the 1 TeV run of the ILC with the integrated luminosity of 1 ab^{1}, production processes of an additional Higgs boson associated with the top quark can be useful as discovery channels in some parameter spaces where the LHC with the integrated luminosity of 3000 fb^{1} cannot reach. It is emphasized that the complementary study at the LHC and the ILC is useful not only to survey additional Higgs bosons at the TeV scale, but also to discriminate types of Yukawa interaction in the 2HDM. 
 [Show abstract] [Hide abstract]
ABSTRACT: This report summarizes the work of the Energy Frontier Higgs Boson working group of the 2013 Community Summer Study (Snowmass). We identify the key elements of a precision Higgs physics program and document the physics potential of future experimental facilities as elucidated during the Snowmass study. We study Higgs couplings to gauge boson and fermion pairs, double Higgs production for the Higgs selfcoupling, its quantum numbers and $C\!P$mixing in Higgs couplings, the Higgs mass and total width, and prospects for direct searches for additional Higgs bosons in extensions of the Standard Model. Our report includes projections of measurement capabilities from detailed studies of the Compact Linear Collider (CLIC), a GammaGamma Collider, the International Linear Collider (ILC), the Large Hadron Collider HighLuminosity Upgrade (HLLHC), Very Large Hadron Colliders up to 100 TeV (VLHC), a Muon Collider, and a TripleLarge Electron Positron Collider (TLEP). 
Article: ILC Higgs White Paper
[Show abstract] [Hide abstract]
ABSTRACT: The ILC Higgs White Paper is a review of Higgs Boson theory and experiment at the International Linear Collider (ILC). Theory topics include the Standard Model Higgs, the twoHiggs doublet model, alternative approaches to electroweak symmetry breaking, and precision goals for Higgs boson experiments. Experimental topics include the measurement of the Higgs cross section times branching ratio for various Higgs decay modes at ILC center of mass energies of 250, 500, and 1000 GeV, and the extraction of Higgs couplings and the total Higgs width from these measurements. Luminosity scenarios based on the ILC TDR machine design are used throughout. The gammagamma collider option at the ILC is also discussed.  [Show abstract] [Hide abstract]
ABSTRACT: We propose a new method to measure various physical parameters, using characteristic weight functions. This method requires only lepton energy distribution and ideally it does not depend on the velocity of the parent particle. We demonstrate an application of this method by simulating a reconstruction of the Higgs boson mass in the H> WW > lnu lnu decay mode at the LHC. We show that systematic errors are suppressed compared to statistical errors. In the vector boson fusion channel, the statistical accuracy of the mass determination is estimated to be +12% and 14% at an integrated luminosity of 100fb^{1}, assuming the Higgs boson mass to be 125GeV and root{s}=14TeV.  [Show abstract] [Hide abstract]
ABSTRACT: In the two Higgs doublet model, $\tan\beta$ is an important parameter, which is defined as the ratio of the vacuum expectation values of the doublets. We study how accurately $\tan\beta$ can be determined at linear colliders via the precision measurement of the decay branching fraction of the standard model (SM) like Higgs boson. Since the effective coupling constants of the Higgs boson with the weak gauge bosons are expected to be measured accurately, the branching ratios can be precisely determined. Consequently, $\tan\beta$ can be determined with a certain amount of accuracy. Comparing the method to those using direct production of the additional Higgs bosons, we find that, depending on the type of Yukawa interactions, the precision measurement of the decay of the SMlike Higgs boson can be the best way to determine $\tan\beta$, when the deviations in the coupling constants with the gauge boson from the SM prediction are observed at linear colliders.  [Show abstract] [Hide abstract]
ABSTRACT: In this Letter, we study the latest bound on the mass of doubly charged Higgs bosons, $H^{\pm\pm}$, assuming that they dominantly decay into a diboson. The new bound is obtained by comparing the inclusive searches for events with a samesign dilepton by the ATLAS Collaboration using the latest 20.3 fb$^{1}$ data at the LHC 8 TeV run with theoretical prediction based on the Higgs triplet model with nexttoleading order QCD corrections. We find that the lower mass bound on $H^{\pm\pm}$ is about 84 GeV.  [Show abstract] [Hide abstract]
ABSTRACT: We study collider signatures for extra scalar bosons in the inert doublet model at the international linear collider (ILC). The inert doublet model is a simple extension of the standard model by introducing an additional isospindoublet scalar field which is odd under an unbroken Z_2 symmetry. The model predicts four kinds of Z_2odd scalar bosons, and the lightest of them becomes stable and a candidate of the dark matter as long as it is electrically neutral. Taking into account the constraints from various theoretical and phenomenological conditions, we perform a simulation study for the distinctive signatures of the extra scalars over the standardmodel background contributions at the ILC with the centerofmass energy of sqrt{s} = 250 GeV and 500 GeV. We further discuss observables for determination of the mass of the scalars. We find that the parameter regions which cannot be detected at the large hadron collider can be probed at the ILC.  [Show abstract] [Hide abstract]
ABSTRACT: We present search prospects and phenomenology of doubly resonant signals that come from the decay of a neutral weaksinglet coloroctet vector state \omega_8 into a lighter weaktriplet coloroctet scalar \pi_8, which can arise in several theories beyond the Standard Model. Taking m_{\omega_8}m_{\pi_8}>m_W, we demonstrate an analysis of the signals pp \to \omega_8 \to \pi^\pm_8 W^\mp (\pi^0_8 Z) \to g W^\pm W^\mp (g Z Z). The present 8 TeV LHC run is found to have the potential to exclude or discover the signal for a range of masses and parameters. The preferred search channel has a boosted Wtagged jet forming a resonance with a second hard jet, in association with a lepton and missing energy.  [Show abstract] [Hide abstract]
ABSTRACT: The doubly charged scalar boson (H^{\pm\pm}) is introduced in several models of the new physics beyond the standard model. The H^{\pm\pm} has Yukawa interactions with two lefthanded charged leptons or two righthanded charged leptons depending on the models. We study kinematical properties of H^{\pm\pm} decay products through tau leptons in order to discriminate the chiral structures of the new Yukawa interaction. The chirality of tau leptons can be measured by the energy distributions of the tau decay products, and thus the chiral structure of the new Yukawa interaction can be traced in the invariantmass distributions of the H^{\pm\pm} decay products. We perform simulation studies for the typical decay patterns of the H^{\pm\pm} with simple event selections and tautagging procedures, and show that the chiral structure of the Yukawa interactions of H^{\pm\pm} can be distinguished by measuring the invariantmass distributions.
Publication Stats
559  Citations  
169.51  Total Impact Points  
Top Journals
Institutions

20132015

University of Toyama
Тояма, Toyama, Japan


20122015

Toyama University
Тояма, Toyama, Japan


20112012

National Taiwan University
 Department of Physics
T’aipei, Taipei, Taiwan


20072011

CERN
 Physics Department (PH)
Genève, Geneva, Switzerland


2006

Niigata University
 Department of Physics
Niahiniigata, Niigata, Japan


20042005

RIKEN
 Radiation Laboratory
Вако, Saitama, Japan


20022005

Hiroshima University
Hirosima, Hiroshima, Japan
