記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of High Energy Physics  

Abstract: A two Higgs doublet model (2HDM) is one of minimal extensions of the Standard Model (SM), and it is well-known that the general setup predicts the flavor-violating phenomena, mediated by neutral Higgs interactions. Recently the CMS collaboration has reported an excess of the lepton-flavor-violating Higgs decay in h → μτ channel with a significance of 2.4 σ. We investigate the CMS excess in a general 2HDM with tree-level Flavor Changing Neutral Currents (FCNCs), and discuss its impact on the other physical observations. Especially, we see that the FCNCs relevant to the excess can enhance the neutral Higgs contributions to the muon anomalous magnetic moment, and can resolve the discrepancy between the measured value and the SM prediction. We also find that the couplings to be consistent with the anomaly of the muon magnetic moment as well as the CMS excess in h → μτ predict the sizable rate of τ → μγ, which is within the reach of future B factory.

DOI： 10.1007/JHEP05(2015)028

Web of Science

Scopus

記述言語：日本語   出版者・発行元：Proceedings of Science  

In a general two Higgs double model, flavor-changing phenomena mediated by neutral Higgs bosons are predicted. We find the μ - τ flavor-violating Higgs interactions in a general Higgs doublet model can explain the excess event in a Higgs decay h → μτ observed by the CMS collaboration as well as the anomaly of the muon anomalous magnetic moment, simultaneously. We also discuss that the predicition of τ → μγ in the scenario can be within the reach of the future B-factory.

Scopus

記述言語：日本語   出版者・発行元：Journal of High Energy Physics  

In this paper, we consider phenomenology of a model with an Lμ - Lτ gauge symmetry. Since the muon couples to the Lμ - Lτ gauge boson (called Z00 boson), its contribution to the muon anomalous magnetic moment (muon g-2) can account for the discrepancy between the standard model prediction and the experimental measurements. On the other hand, the Z00 boson does not interact with the electron and quarks, and hence there are no strong constraints from collider experiments even if the Z00 boson mass is of the order of the electroweak scale. We show an allowed region of a parameter space in the Lμ - Lτ symmetric model, taking into account consistency with the electroweak precision measurements as well as the muon g-2. We study the Large Hadron Collider (LHC) phenomenology, and show that the current and future data would probe the interesting parameter space for this model. Open Access, © 2014 The Authors.

DOI： 10.1007/JHEP03(2014)105

Web of Science

Scopus

記述言語：日本語   出版者・発行元：Proceedings of Science  

An anomaly of the muon anomalous magnetic moment (muon g-2) has been reported. The discrepancies between the Standard Model (SM) prediction and the measured value are about 3-4 s. If this anomaly is due to new physics beyond the SM, we expect new particles and interactions related with the muon sector. In this talk, we consider a model with an Lµ - Lt gauge symmetry. Since the muon couples to the Lµ - Lt gauge boson (called Z" boson), its contribution to the muon g-2 can account for the discrepancy. On the other hand, the Z" boson does not interact with the electron nor quarks, and hence there are no strong constraints from collider experiments even if the Z" boson mass is of the order of the electroweak scale. We show an allowed region of a parameter space in the model, taking into account consistency with the electroweak precision measurements as well as the muon g-2. We study the Large Hadron Collider (LHC) phenomenology, and show that the current and future data would probe the interesting parameter space for this model.

Scopus

記述言語：日本語   出版者・発行元：Physical Review D - Particles, Fields, Gravitation and Cosmology  

About 3σ deviation from the standard model prediction of muon anomalous magnetic moment (muon g-2) has been reported. We consider new physics beyond the standard model which has new Yukawa interactions with muons. We compute new contributions to muon g-2 and corrections to electroweak observables, and show the consistent region of parameter space. We find that in a simple model where the chirality flip of a muon occurs only in the external muon line in one-loop muon g-2 diagrams, it is necessary to introduce the relatively large new Yukawa coupling and the electroweak scale new particles. On the other hand, in a model where the chirality flip can occur in the internal fermion line of one loop muon g-2 diagrams, we can obtain favorable g-2 contributions without large Yukawa coupling, and they are consistent with the precision electroweak observables. Finally, we discuss effects of new particles for muon g-2 on the Higgs boson decay h→γγ and direct productions of these particles at the LHC experiment. © 2012 American Physical Society.

DOI： 10.1103/PhysRevD.86.095025

Web of Science

Scopus

担当区分：筆頭著者   記述言語：日本語  

LEP実験のヒッグス粒子の制限を見直し、超対称理論での軽いヒッグス粒子の可能性を議論する。

記述言語：英語  

The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Super-beams, Laboratori Nazionali di Frascati, Rome, 21–26 June 2005) and NuFact06 (Ivine, CA, 24–30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second-generation super-beam experiments, beta-beam facilities and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report.

担当区分：筆頭著者   記述言語：英語  

In this talk, I discuss important roles of precision measurements on the muon properties, such as muon lifetime, muon anomalous magnetic moment (muon g-2) and muon rare decay (µe etc.) to test the standard model of elementary particles and to search for new physics effects. I stress that even after discovering new physics effects at the LHC, these studies on muons will be complementary to the LHC physics, and therefore, the further experimental studies on muons will be very important to understand the more fundamental theory of elementary particles.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We show that in the Minimal Supersymmetric Standard Model, the possibility for the lightest CP-even Higgs boson to be lighter than $Z$ boson (as low as about 60 GeV) is, contrary to the usual belief, not yet excluded by LEP2 data or any other existing experimental data. The characteristic of the light Higgs boson scenario (LHS) is that the $ZZh$ coupling and the decay branching ratio ${\rm Br}(h/A\to b\bar{b})$ are simultaneously suppressed as a result of generic supersymmetric loop corrections. Consequently, the $W^\pm H^\mp h$ coupling has to be large due to the sum rule of Higgs couplings to weak gauge bosons. In addition to discussing the potential of the Tevatron and $B$-factories to test the LHS, we show that the associate neutral and charged Higgs boson production process, pp\to H^\pm h (A)$, can completely probe LHS at the CERN Large Hadron Collider.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In the framework of the littlest Higgs model with T parity (LHT), we study the production processes of T-even (T+) and T-odd (T-) partners of the top quark at the Large Hadron Collider (LHC). We show that the signal events can be distinguished from the standard model backgrounds, and that information about mass and mixing parameters of the top partners can be measured with relatively good accuracies. With the measurements of these parameters, we show that a nontrivial test of the LHT can be performed. We also discuss a possibility to reconstruct the thermal relic density of the lightest T-odd particle AH using the LHC results and show that the scenario where AH becomes dark matter may be checked.

担当区分：筆頭著者   記述言語：英語  

We study Higgs boson production and decay in a certain class of Little Higgs models with T-parity where T-parity fermionic partners of the Standard Model (SM) fermions gain their mass through Yukawa-type interactions. We find that the Higgs boson production cross section at the CERN LHC via gluon-gluon fusion process could be significantly reduced, as compared to its SM prediction, for a relatively low new particle scale. On the other hand, the Higgs boson production cross section via weak boson fusion process is very close to the SM value. Furthermore, the Higgs boson decay branching ratio into -mode could be largely enhanced in small Higgs boson mass region in a certain case because the total decay width of Higgs boson in the Little Higgs model is smaller than that in the SM.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

We study the collider phenomenology of a Littlest Higgs model with T-parity. We first stress the important role of the T-odd SU(2) doublet fermions (introduced to make the model T-parity invariant) in high energy scattering processes, such as $q\bar{q}\to W_H^+ W_H^-$ where $W_H^\pm$ are the T-odd partners of $W$-bosons. Because the mass of the T-odd SU(2) doublet fermions cannot be too heavy to be consistent with low energy data, they can be copiously produced at the CERN Large Hadron Collider (LHC). Therefore, we study the collider phenomenology of the model with emphasis on the contributions of the T-odd fermion to the production of the heavy T-parity partners (either bosons or fermions) of the usual particles at the LHC. The production cross sections and the decay branching ratios of the new heavy particles are classified and various experimental signatures are discussed.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

We study Higgs boson production and decay in a certain class of Little Higgs models with T-parity in which some T-parity partners of the Standard Model (SM) fermions gain their masses through Yukawa-type couplings. We find that the Higgs boson production cross section of a 120 GeV Higgs boson at the CERN LHC via gg fusion process at one-loop level could be reduced by about 45%, 35% and 20%, as compared to its SM prediction, for a relatively low new particle mass scale f = 600, 700 and 1000 GeV, respectively. On the other hand, the weak boson fusion cross section is close to the SM value. Furthermore, the Higgs boson decay branching ratio into di-photon mode can be enhanced by about 35% in small Higgs mass region in certain case, for the total decay width of Higgs boson in the Little Higgs model is always smaller than that in the SM.

開催年月日： 2015年6月

記述言語：英語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2015年5月

記述言語：英語   会議種別：ポスター発表  

国名：日本国  

開催年月日： 2014年7月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催地：Peking University, China   国名：中華人民共和国  

開催年月日： 2013年1月

記述言語：英語   会議種別：口頭発表（一般）  

国名：中華人民共和国  

開催年月日： 2010年12月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催年月日： 2009年4月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2008年9月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2008年9月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2008年3月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2007年9月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催年月日： 2007年8月

記述言語：英語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2007年7月

記述言語：英語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2007年6月

記述言語：英語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2007年6月

記述言語：英語   会議種別：口頭発表（招待・特別）  

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催地：Peking University, China  

記述言語：日本語   会議種別：口頭発表（招待・特別）  

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Sanya, China  

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催地：茨城県東海村 J-PARC  

記述言語：日本語   会議種別：口頭発表（招待・特別）  

開催地：東京大学 本郷  

記述言語：英語   会議種別：ポスター発表  

開催地：Nagoya  

記述言語：英語   会議種別：口頭発表（招待・特別）  

記述言語：英語   会議種別：口頭発表（招待・特別）  

量子力学I、解析力学IIの演習

素粒子の標準模型の、ニュートリノやヒッグス粒子に関するトピックスを紹介する。

素粒子物理の教科書を輪講する。

素粒子の標準模型の基礎となる場の量子論などを紹介する。