セミナー

Andrey Tayduganov

Determining the photon polarization of the $b¥to s¥gamma$ using the $B¥to K_1(1270)¥gamma¥to(K¥pi¥pi)¥gamma$ decay

Seminar hall, 4 go-kan
Recently the radiative $B$ decay to the strange axial-vector mesons, $B¥to K_1(1270) ¥gamma$, has been observed with rather large rate. This process is particularly interesting as the subsequent $K_1$ decay into its three body final state allows to determine the polarization of the gamma, which is mostly left- (right-)handed for $¥overline{B} (B)$ in the SM while various new physics models predict additional right- (left-)handed components. A new method is proposed to determine the polarization, exploiting the full Dalitz plot distribution, which seems to reduce strongly the statistical errors. In order to obtain a theoretical prediction for this polarization measurement, it is necessary to understand the hadronic $K_1 ¥to K ¥pi ¥pi$ decay channel and its uncertainties. The strong decays of the $K_1$ mesons, namely the partial wave amplitudes as well as their relative phases, are revisited in the framework of the $^3P_0$ quark-pair-creation model. Then, the result on the sensitivity of the $B¥to K_1(1270) ¥gamma$ process to the photon polarization is presented.

Tsuyoshi Houri, Osaka City University

Geometrization of Hamiltonian Dynamics and Hidden Symmetry of Space-times

Meeting room 1, Kenkyu honkan 1F
It is known that motion of free particles in curved space-times is deeply connecting with symmetry of space-times. In particular, it has been revealed that besides isometry “hidden symmetry” is important in black hole space-times since it was discovered first in Kerr space-time. Therefore it is interesting question to study how hidden symmetry works in higher-dimensional black hole space-times. In this talk, we will study hidden symmetry of five-dimensional black ring space-times together with a “Geomtrization” method. According to Maupertuis’ principle, Hamiltonian dynamics result in geodesic problems on the corresponding manifolds, which is called “Geometrization.” In the first half of this talk, beginning with a review of hidden symmetry, we will introduce the geometrization carefully. After that, hidden symmetry of five-dimensional black ring space-times will be discussed.

Kentaroh Yoshida, Kyoto University

Classical integrable structure of deformed sigma models

Meeting room 1, Kenkyu honkan 1F
We show that Yangian x quantum group symmetries are realized in two-dimensional sigma models whose target spaces are three-dimensional squashed spheres, warped AdS spaces and Schrodinger spacetimes. These symmetries enable us to develop two descriptions to describe its classical dynamics, according to the left and right symmetries. Each of the Lax pairs constructed in both ways leads to the same equations of motion. The two descriptions are related one another through a non-local map.

Kunihisa Morita, Waseda Institute for Advanced Study

時間対称化された量子力学の解釈

Seminar room, Kenkyu honkan 3F
量子力学の解釈問題において,状態の収縮を認めるか否かは重要な争点のひとつである.また,状態の収縮を認めない場合,では,物理量が測定前は明確な値をもたない物理量をもたないのに,どのようにして,測定後は明確な値をもつようになるのか,ということに答えることができなければならない.そのひとつの回答として,アハラノフらの時間対称化された量子力学(二状態ベクトル形式)をベースにした時間対称化された解釈について議論する.

坂口貴男, Brookhaven National Laboratory

電磁プローブによる重イオン衝突の研究

Seminar room, Kenkyu honkan 3F
2000年よりRHICで始まった重イオン衝突の実験においては、これまで生成量が小さかったために困難であった、ハード過程を利用した研究が可能となった。衝突でできた高温高密度物質と、ハード過程で散乱されたパートンの相互作用によって起きた、高横運動量ハドロンの収量の抑制は、この研究手法における大きな成果の一つであるが、その解釈を決定的にしたのが、衝突初期の情報をそのまま持ち出す単光子の測定である。 単光子は衝突初期から、系がハドロン化するまでに、連続的に放射されるため、重イオン衝突を系統的に研究する、最適のプローブである。 本講演では、重イオン衝突における単光子測定の歴史と、その測定手法、そしてRHICにおける最新の測定結果を紹介する。

Handhika Satrio Ramadhan, LIPI

Exotic Transitions in 6d Flux Compactifications

Room 345, 4 go-kan
“We present two profound tunneling phenomena in 6d Toy Model of Flux compactification. The first is a non-perturbative instability of the flux vacua, where the tunneling is achieved by dropping all the flux altogether and tunnel to no-flux state. We found that this state is a state with no (classical) space-time. It is a tunneling to Nothing, i.e., a bubble of nothing (reminiscent to the Wittens bubble of nothing). The second is the reverse-process, i.e., that the flux vacua can be spontaneously created from Nothing. We dubbed it Bubble from Nothing. Finally we show that a bubble from nothing is stable against nucleation of bubble of nothing, and in fact there is a smooth transition between the two.”

Mitsuru Kakizaki, Toyama University

Dark matter in UED : the role of the second KK level

Room 345, 4 go-kan
We perform a complete calculation of the relic abundance of the KK-photon LKP in the universal extra dimension model including all coannihilation channels and all resonances. We show that the production of level 2 particles which decay dominantly into SM particles contribute significantly to coannihilation processes involving level 1 KK-leptons. As a result the preferred dark matter scale is increased to R^{-1}=1.3 TeV. A dark matter candidate at or below the TeV scale can only be found in the non-minimal model by reducing the mass splittings between the KK-particles and the LKP. The LKP nucleon scattering cross section is typically small, ¥sigma <10^{-10} pb, unless the KK-quarks are nearly degenerate with the LKP.

Shuichiro Yokoyama, Nagoya University

初期揺らぎの非ガウス性と構造形成

Meeting room 1, Kenkyu honkan 1F
近年の宇宙論的観測の進歩により、現在の宇宙の構成要素だけでなく、初期宇宙の物理にも迫る研究が盛んに行われている。特に初期揺らぎの情報から、初期宇宙の重要なパラダイムの一つであるインフレーション理論に対してより詳細な議論が可能となることが期待されている。そのような現状において、初期揺らぎの非ガウス性が注目を集めている。線形摂動論+量子ゆらぎ起源という仮定のもとでは、初期揺らぎはガウス統計に従うと考えられるが、一般に揺らぎの発展が従うアインシュタイン方程式は非線形方程式であるし、場の相互作用を通じて、非ガウス性は生じる。精密観測により、この非ガウス性を精査することで、初期宇宙の新たな物理が見えてくることが期待される。例えば、宇宙背景輻射の観測では、温度揺らぎの三点相関が有力な観測量となる。また大規模構造形成のシナリオにも様々な影響を与える。本セミナーでは、この初期揺らぎの非ガウス性について、簡単なレビューをし構造形成にどのような影響を与えるかを議論する。

Takashi Shimomura, Niigata University

Constraining the Higgs masses from false vacua in the NMSSM.

Meeting room 1, Kenkyu honkan 1F
We analyze a vacuum structure of the Higgs sector in the Next-to Minimal Supersymmetric Standard Model (NMSSM). We show that some minima, which can be identified as false vacua, can be found analytically along specific directions. These minima can become deeper than the true vacuum or the electroweak symmetry breaking vacuum. Such minima should be avoided to ensure the stability of the true vacuum, resulting in constraints on the parameters of the NMSSM. The masses of the Higgses can be restricted using the constraints. We show that the Higgs masses can not be heavy so much in some parameter regions even in the NMSSM.

Kenji Ogawa, National Chiao-Tung University/KEK-NCTS exchange program visitor

The lattice study of many flavor QCD with twisted boundary condition

Meeting room 1, Kenkyu honkan 1F
Incorporated with twisted boundary condition, Polyakov loop correlators can give a definition of renormalized coupling. We employ this scheme for step scaling function in the search of conformal fixed point. Staggered fermion and plaquette gauge action are used in the lattice simulation with six different lattice sizes L = 20, 16, 12, 10, 8 and 6. For the largest lattice size L = 20, we used a large number of GPU’s and accumulated 3,000,000 trajectories in total. We found that the step scaling function sigma(u) is consistent with u in the low beta region. It strongly suggests the existence of conformal fixed point. Some details of our analysis and simulations will also be presented.

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