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Theses

• Graduation Work Linear Collider —to-> Relic Density [In Japanese]
• Magisterial Thesis Supersymmetry without R-Parity: Its Phenomenology

2010

• Lepton Flavor Violation and Cosmological Constraints on R-parity Violation.
  Motoi Endo, Koichi Hamaguchi and Sho Iwamoto. JCAP 1002:032 [arXiv:0912.0585].

2011

• Stau Kinks at the LHC.
  Shoji Asai, Yuya Azuma, Motoi Endo, Koichi Hamaguchi and Sho Iwamoto. JHEP 1112 (2011) 041 [arXiv:1103.1881].
• Higgs Mass and Muon Anomalous Magnetic Moment in Supersymmetric Models with Vector-Like Matters.
  Motoi Endo, Koichi Hamaguchi, Sho Iwamoto and Norimi Yokozaki. Phys. Rev. D 84, 075017 [arXiv:1108.3071].
• LHC Dijet Signals in New Physics Models for Top Forward-Backward Asymmetry.
  Motoi Endo and Sho Iwamoto. [arXiv:1110.0014].
• Higgs mass, muon g-2, and LHC prospects in gauge mediation models with vector-like matters.
  Motoi Endo, Koichi Hamaguchi, Sho Iwamoto and Norimi Yokozaki. Phys. Rev. D 85, 095012 [arXiv:1112.5653].
• Higgs mass and muon anomalous magnetic moment in the U(1) extended MSSM.
  Motoi Endo, Koichi Hamaguchi, Kazunori Nakayama, Sho Iwamoto and Norimi Yokozaki. Phys. Rev. D 85, 095006 [arXiv:1112.6412].

2012

• Vacuum Stability Bound on Extended GMSB Models.
  Motoi Endo, Koichi Hamaguchi, Sho Iwamoto and Norimi Yokozaki. [arXiv:1202.2751].

Graduation Work (2008) "Linear Collider —to-> Relic Density"

The work I did in the "Undergraduate Research"   course; this work was supervised by Dr. Masako Iwasaki, a lecturer of Aihara Lab. (lab on experimental particle physics).

We followed the work by Feng and Peskin, and showed how precisely we can measure the mass of the superpaticles with the International Linear Collider.

This report is written in Japanese.

Magisterial Thesis (2010) "Supersymmetry without R-Parity: Its Phenomenology"

The magisterial thesis, mainly focused on my previous work; supervised by Prof. Koichi Hamaguchi.

We in this paper reviewed the R-parity violation, symmetries imposed instead of the R-parity, and experimental constraints on the R-parity violating couplings; then we, as done in the previous work, but more pedagogically, discuss cosmological constraints on the couplings which become severe in the presence of lepton flavor violation.

We investigate in detail the R-parity violating SUSY, especially the constraints on its parameters. The constraints are mainly obtained from collider experiments, and they are of order 10^-3-10^-4. However, we found that, if lepton flavor violating processes are strong enough to equilibrate the lepton flavor asymmetry in the early universe, which is naturally expected in various models, the present baryon–antibaryon asymmetry brings us much more stringent constraints of order 10^-6-10^-7.

Lepton Flavor Violation and Cosmological Constraints on R-parity Violation

In this paper we discussed the cosmological constraints on the R-parity violation. You can find more pedagogical discussion in my magisterial thesis, Section 3 and 4; it would be a great help if you are new to this topic, although it is not so sophisticated as that in this paper...

In supersymmetric standard models R-parity violating couplings are severely constrained, since otherwise they would erase the existing baryon asymmetry before the electroweak transition. It is often claimed that this cosmological constraint can be circumvented if the baryon number and one of the lepton flavor numbers are sufficiently conserved in these R-parity violating couplings, because for each lepton flavor is separately conserved by the sphaleron process. We discuss the effect of lepton flavor violation on the conservation, and show that even tiny slepton mixing angles and will spoil the separate conservation. In particular, if lepton flavor violations are observed in experiments such as MEG and B-factories, it will imply that all the R-parity violating couplings must be suppressed to avoid the erasure. We also discuss the implication for the decay of the lightest MSSM particle at the LHC.

Stau Kinks at the LHC

In this paper is discussed "kink tracks", an exotic signature detected by the TRT (ATLAS/LHC). Especially we discuss stau kink tracks, focusing on the following two models: (1) SUSY with a stau MSSM-LSP, R-parity violated in or ; (2) SUSY with a gravitino LSP, a stau NLSP. Roughly speaking, if in (1), or if in (2), we would be achieve discovery of such kink signatures with 14TeV LHC.

I want to emphasize two points. The one is that this approach is very effective to find long-lived staus (). The other is that the reach of (1) is the favored region with respect to the discussion in my previous paper.

We investigate the possibility of probing SUSY models by analyzing the kink signatures of charged tracks at the LHC. As underlying models, we consider two models, SUSY models with a gravitino LSP and a stau NLSP, and R-parity violating SUSY models with a stau (N)LSP. We show that, if the decay length is , a large number of kink events can be discovered in a wide range of the SUSY parameters. We also discuss model discrimination by identifying the daughter particles of the kink tracks.

Higgs Mass and Muon Anomalous Magnetic Moment in Supersymmetric Models with Vector-Like Matters

We had, in 2012 summer, some 2 sigma indication of 130-140 GeV Higgs. It was extremely heavier than expected, and if we assume the MSSM framework, such mass cannot be achieved without very very fine tuning, which was of a great depression. This depression stands out with taking the muon g-2 anomaly into consideration, which requires a much lighter SUSY scale.

So we extend the MSSM with , or extra vector-like quarks. Such extra matters yields coupling, which drastically lifts up the Higgs mass with the same mechanism as , and with the help we can keep the SUSY scale lighter to achieve the SUSY explanation of the muon anomaly.

The 130-140 GeV Higgs signal disappeared soon, actually died at a few months, as is usual for 2-sigma excesses, but this framework was used in the next paper.

We study the muon anomalous magnetic moment (muon ) and the Higgs boson mass in a simple extension of the minimal SUSY Standard Model with extra vector-like matters, in the frameworks of GMSB models and mSUGRA models. It is shown that the deviation of the muon and a relatively heavy Higgs boson can be simultaneously explained in large region. (i) In GMSB models, the Higgs mass can be more than 135 GeV (130 GeV) in the region where muon is consistent with the experimental value at the () level, while maintaining the perturbative coupling unification. (ii) In the case of mSUGRA models with universal soft masses, the Higgs mass can be as large as about 130 GeV when muon is consistent with the experimental value at the level. In both cases, the Higgs mass can be above 140 GeV if the constraint is not imposed.

LHC Dijet Signals in New Physics Models for Top Forward-Backward Asymmetry

It is shown that the flavor changing model, which can be explain the anomalies in the top forward-backward asymmetry, gives a signature on the dijet () measurement in the LHC experiment.

This means the LHC experiment would give another clue than the charge asymmetry to explore the origin of the anomaly, which is quite important in this era where the Tevatron unfortunately shut down.

Actually I have done many analyses besides shown in this letter, which I would give in some talks :)

The dijet signature at the LHC is studied in new physics models for the top forward-backward asymmetry at the Tevatron. In the -mediator models, flavor-changing interactions contribute to the dijet production cross section as well as the asymmetry at least at the one-loop level. It is found that the LHC dijet measurements at have constrained the coupling larger than 2.5-3. The sensitivity is expected to be improved significantly as the integrated luminosity increases in the LHC.

Higgs mass, muon g-2, and LHC prospects in gauge mediation models with vector-like matters

The 130-140 GeV Higgs died soon, but after a few months we found excesses of around 125 GeV.

Even for 125 GeV, it is difficult to realize the simultaneous explanation of the Higgs mass and the muon anomaly. It can be achieved with setting the gluino mass heavier than the bino/wino mass, or setting the 3rd-generation scalar mass heavier than the 1st and 2nd generation mass, at the GUT scale. It is somewhat peculiar for us, and thus we dug up the previous framework which we proposed for 130-140 GeV Higgs. It allows us to achieve the simultaneous explanation within the framework of the GMSB and the CMSSM.

We also discuss LHC prospects; SUSY searches and 4th generation quark searches. The SUSY searches give lower bounds on the SUSY scale (depending on the signature, or the MSSM-LSP and its lifetime) even with a dataset corresponds to . The 4th generation searches have yielded no general bound because the extra vector-like matters have several decay branch, but assuming the decay products several mass bounds can be obtained; here we would like to emphasize the importance of the search for signature.

Recently the ATLAS and CMS collaborations presented preliminary results of Standard Model Higgs searches and reported excesses of events for a Higgs boson at 124-126 GeV. Such a Higgs mass can be naturally realized, simultaneously explaining the muon anomaly, in gauge-mediated SUSY breaking models with extra vector-like matters. Upper bounds are obtained on the gluino mass, , and on the extra vector-like quark mass, , in the parameter region where the Higgs boson mass is 124-126 GeV and the muon is consistent with the experimental value at the level. The LHC prospects are explored in the parameter region. It is found that some of the regions are already excluded by the LHC, and most of the parameter space is expected to be covered at A study on the extra vector-like quarks, especially current bounds on their masses and prospects for future searches, is also included.

mass and muon anomalous magnetic moment in the U(1) extended MSSM

TBW

We study phenomenological aspects of the MSSM with extra U(1) gauge symmetry. We find that the lightest Higgs boson mass can be increased up to 125 GeV, without introducing a large SUSY scale or large A-terms, in the frameworks of the CMSSM and gauge mediated SUSY breaking (GMSB) models. This scenario can simultaneously explain the discrepancy of the muon anomalous magnetic moment (muon ) at the level, in both of the frameworks, U(1)-extended CMSSM/GMSB models. In the CMSSM case, the dark matter abundance can also be explained.

Vacuum Stability Bound on Extended GMSB Models

TBW

Extensions of GMSB models were recently explored to explain the recent reports of the Higgs boson mass around 124-126 GeV. Some models predict a large term, which can spoil the vacuum stability of the universe. We study two GMSB extensions: i) the model with a large trilinear coupling of the top squark, and ii) that with extra vector-like matters. In both models, the vacuum stability condition provides upper bounds on the gluino mass if combined with the muon . The whole parameter region is expected to be covered by LHC at . The analysis is also applied to the mSUGRA models with the vector-like matters.

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