[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 non-decoupling 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 electron-positron
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 multi-top-quarks
events at the LHC Run-II, 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 multi-top-quarks 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.
[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 three-momenta and angular momenta are reversed. Perturbative QCD predicts nonzero polarization at the one-loop level, which can be measured as parity-odd components in the angular distribution of charged leptons from the decay of W bosons. We perform a detector-level 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 one-loop QCD amplitudes.
[Show abstract][Hide abstract] ABSTRACT: In this report, selected topics of tau leptons are collected in view of the high-energy collider experiments and the Higgs-boson search. Those topics include decay modes, tau-jet 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$\ddot{\i}$ve-T-reversal where both the three-momenta and
angular momenta are reversed. Perturbative QCD predicts non-zero polarization
at the one-loop level, which can be measured as parity-odd components in the
angular distribution of charged leptons from the decay of W bosons. We perform
a detector-level 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 one-loop QCD amplitudes.
[Show abstract][Hide abstract] ABSTRACT: After the discovery of the standard-model-like 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 softly-broken $Z_2$ 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 softly-broken 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
standard-model-like 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 high-luminosity run or at the
International Linear Collider, we can identify the non-minimal Higgs sector
even without direct discovery of additional Higgs bosons at the LHC.
Physical Review D 06/2014; 90(7). DOI:10.1103/PhysRevD.90.075001 · 4.64 Impact Factor
[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
standard-model (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.
[Show abstract][Hide abstract] ABSTRACT: We propose a new method to measure a theoretically well-defined 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.
[Show abstract][Hide abstract] ABSTRACT: We propose a new method to measure a theoretically well-defined 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.
Physics Letters B 04/2014; 741. DOI:10.1016/j.physletb.2014.12.044 · 6.13 Impact Factor
[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 softly-broken 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.
Nuclear Physics B 04/2014; 886. DOI:10.1016/j.nuclphysb.2014.07.007 · 3.93 Impact Factor
[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 softly-broken 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 self-coupling, 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 Gamma-Gamma Collider, the
International Linear Collider (ILC), the Large Hadron Collider High-Luminosity
Upgrade (HL-LHC), Very Large Hadron Colliders up to 100 TeV (VLHC), a Muon
Collider, and a Triple-Large Electron Positron Collider (TLEP).
[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 two-Higgs 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 gamma-gamma 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.
Journal of High Energy Physics 05/2013; 2013(8). DOI:10.1007/JHEP08(2013)129 · 6.11 Impact Factor
[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 SM-like 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
same-sign 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 next-to-leading order QCD corrections. We find that the
lower mass bound on $H^{\pm\pm}$ is about 84 GeV.
Physics Letters B 05/2013; 726(1-3). DOI:10.1016/j.physletb.2013.08.054 · 6.13 Impact Factor
[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
isospin-doublet scalar field which is odd under an unbroken Z_2 symmetry. The
model predicts four kinds of Z_2-odd 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 standard-model background
contributions at the ILC with the center-of-mass 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.
Physics Letters B 03/2013; 725(4-5). DOI:10.1016/j.physletb.2013.07.011 · 6.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present search prospects and phenomenology of doubly resonant signals that
come from the decay of a neutral weak-singlet color-octet vector state \omega_8
into a lighter weak-triplet color-octet 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 W-tagged 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 left-handed charged leptons or two right-handed 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
invariant-mass 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 tau-tagging procedures, and show that the chiral structure
of the Yukawa interactions of H^{\pm\pm} can be distinguished by measuring the
invariant-mass distributions.