セミナー 2015年

Yasuaki Hikida, Rikyo U.

N=3 higher spin holography and Higgs phenomenon

Meeting Room 1, Kenkyu-Honkan 1F
Superstring theory includes a lot of massive higher spin excitations, and there would appear a higher spi gauge symmetry at the tensionless limit. Moreover, it has been expected that these states could be described by a broken phase of higher spin gauge theory. Recently, it becomes possible to discuss the realizations of the idea with the help of Vasiliev theory and AdS/CFT correspondence. In this talk, I will explain recent developments on the concrete relation between higher spin gauge theory and superstring theory by making use of AdS/CFT correspondence. In particular, I will focus on the AdS_3 case. Moreover, I will show that higher spin fields become massive due to the braking of higher spin symmetry using a simple example.

Sadakazu Haino, Institute of Physics, Academia Sinica

[Cosmophysics Seminar] The new results from Alpha Magnetic Spectrometer (AMS)

Meeting Room 1, Kenkyu Honkan 1F
The AMS collaboration presented the latest results in its quest to understand the origin of cosmic rays and dark matter. These intriguing results were shared and discussed during the “AMS days” in April/2015. Some detailed discussions on the new results will be made in this seminar.

Biswarup Mukhopadhyaya, Harish-Chandra Research Institute, Allahabad, India

The credibility of SUSY phenomenology: some silver linings

Meeting room 3, Kenkyu Honkan 1F
With mass limits on supersymmetric particles going up, the role of supersymmetry (SUSY) as the prime option for physics beyond the standard model may appear somewhat debatable to some quarters. In this backdrop, we start by briefly touching upon the desirability as well viability of SUSY in the current context. Then we summarise a few recent works, particularly those by our group, where there is a slight departure from the commonest approaches to SUSY phenomenology, be it in logic, motivation or collider signals.

Yukinari Sumino, Tohoku University

Understanding Heavy Quark­AntiQuark System by Perturbative QCD

Meeting room 1, Kenkyu honkan 1F
Due to the discovery of renormalon cancellation, it became possible to describe the nature of a heavy quark­antiquark system (such as bottomonium) based on perturbative QCD, both qualitatively and quantitatively. Accordingly, interpretaions of the heavy quark mass and interquark force have been modified considerably. I overview what has been understood and some of theoretical progress since then. The UV part of the interquark potential can be computed in perturbative QCD. We show that a “Coulomb+linear” potential is obtained as the prediction.

Ryusuke Jinno, The University of Tokyo

Gravitational effects on inflaton decay

Meeting room 1, Kenkyu honkan 1F
The inflaton inevitably couples to all non-conformally coupled matters to gravity, through an oscillation in the Hubble parameter or the cosmic scale factor. This oscillation leads to particle production during the inflaton oscillation regime. In this talk, I first apply the analysis of scalar particle production to the case of minimally-coupled inflaton to gravity, and then extend the analysis to non-minimally coupled case, in which the Hubble parameter oscillates more violently. I also show the analysis of the graviton production by the inflaton in both minimal & non-minimal case.
Reference :
1. Gravitational Effects on Inflaton Decay, Yohei Ema, Ryusuke Jinno, Kyohei Mukaida, Kazunori Nakayama arXiv:1502:02475
2. Yohei Ema, Ryusuke Jinno, Kyohei Mukaida, Kazunori Nakayama, to appear

Vojtech Krejcirik, RIKEN

[cancelled] Few new insights into $\bar{K}N$ interaction

Seminar room, Kenkyu honkan 3F
In this talk, I will report on the recent progress in the analysis of meson-baryon interaction in the strange sector. In the first part, the EFT motivated model taking into account both L=0 and L=1 partial wave will be presented. The model aims at a uniform treatment of both $\Lambda(1405)$ and $\Sigma(1385)$ resonances both in vacuum and in the nuclear medium. The second half of the talk will be devoted to the discussion of lattice QCD approach (HAL QCD approach, in particular) to the problem.

鈴木惇也, 東京大学

[Cosmophysics seminar] Hidden Photon ダークマター探索

Room 345, 4 go-kan 3F
ダークマターの存在はさまざまな観測結果から示唆されており、その直接探索実験は実験物理学の花形の一つとなっている。現在、ダークマターの正体として WIMP を想定し原子核反跳を捉える実験が盛んにおこなわれている。一方、それ以外に axion などの軽い粒子が非熱的に生成されるというシナリオも考えられ、その探索を目指す実験として ADMX などがある。近年、hidden photon (dark photon) も非熱的なシナリオでダークマターになりうることが指摘され、その新奇な探索手法として dish antenna を用いた方法が 提案された。それを受けて我々の研究室では、 ~ eV と ~10^{-5} eV 、2つの hidden photon 質量領域をカバーする2つの実験装置をつくり、その探索を行った。本講演ではダークマターの可能性としての hidden photon について、その実験手法と我々の探索結果についての話をおこなう。

Daisuke Harada, KEK

Phenomenology of Heavy vector-like quarks

Meeting room 1, Kenkyu honkan 1F
K中間子の崩壊におけるCPの破れについて説明するため、クォークの世代数が、少なくとも3世代以上であることが知られている。標準模型の枠内では、4世代目のクォークおよびレプトンが存在してはいけないという理論的な理由は存在しない。しかしながら、最近のLHC実験におけるヒッグス探索の結果によって、4世代目のカイラルなクォークは強く否定されている。この実験によって、4世代目のクォーク自体が否定されているわけではなく、その他の可能性として、ベクターライクフェルミオンが知られている。例えば、リトルヒッグス模型や余剰次元の模型といった様々なNew Physicsの模型において、このようなフェルミオンが導入されている。従って、このようなベクターライクフェルミオンがTeVスケールの物理の与える影響について調べることは非常に興味深い。我々の研究では、個々の模型に依存せずにベクターライクフェルミオンの効果について調べるため、有効模型を用いて、LHC実験における発見可能性やフレーバー物理に与える影響について調査した。セミナーでは、この研究成果について議論する。

Yuichiro Nakai, Harvard University

Deconstruction, Holography and Emergent Supersymmetry

Meeting room 1, Kenkyu honkan 1F
In this talk, we discuss a gauge theory in a 5D warped space via the dimensional deconstruction that a higher dimensional gauge theory is constructed from a moose of 4D gauge groups. By the AdS/CFT
correspondence, a 5D warped gauge theory is dual to a 4D conformal field theory (CFT) with a global symmetry. As far as physics of the gauge theory, we obtain the one-to-one correspondence between each component of a moose of gauge groups and that of a CFT. We formulate a supersymmetric extension
of deconstruction and explore the framework of natural supersymmetry in a 5D warped space – the supersymmetric Randall-Sundrum model with the IR-brane localized Higgs and bulk fermions – via the gauge moose. In this model, a supersymmetry breaking source is located at the end of the moose corresponding to the UV brane and the first two generations of squarks are decoupled. With left-right gauge symmetries in the bulk of the moose, we demonstrate realization of accidental or emergent supersymmetry of the Higgs sector in comparison with the proposed “Moose/CFT correspondence.”

Kohsaku Tobioka, Tel Aviv U., Weizmann, KEK

Probing Higgs-charm coupling, for current and future LHC

Meeting room 1, Kenkyu honkan 1F
We introduce four different types of data­driven analyses that constrain the size of the Higgs­charm Yukawa coupling: (i) recasting the vector­boson associated, Vh, analyses that search for bottom­pair final state; (ii) the direct measurement of the total width; (iii) the search to h­> J/\psi\gamma; (iv) a global fit to the Higgs signal strengths. A comparison with t\bar{t}h data allows us to show that the Higgs does not couple to quarks in a universal way. Finally, we demonstrate how the experimental collaborations can further improve our direct bound (i) using charm­tagging.

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