Andrew Akeroyd, University of Southampton
Decay of charged Higgs bosons into charm and bottom quarks in multi-Higgs doublet models
Meeting room 1, Kenkyu honkan 1F
A scalar particle has been discovered at the Large Hadron Collider (LHC), but it is not yet known if this particle corresponds to the Higgs boson of the Standard Model or if it is the first of many Higgs bosons which are waiting to be discovered. Higgs bosons with electric charge (“charged Higgs bosons” or “charged scalars”) are predicted in many extensions of the Standard Model. Searches for such particles are being carried out at the LHC, in particular in the decays of the top quark, and these searches assume that two specific decay modes of the charged Higgs boson are dominant: In this talk I show that a third decay mode, into charm and bottom quarks, can be dominant in models with more than two Higgs isospin doublets. So far there has been no dedicated search for this decay to charm and bottom quarks at the LHC, but it could readily be performed as an extension of an ongoing search which assumes that the charged Higgs boson decays into a charm quark and a strange quark.
Francesco Knechtli, University of Wuppertal
Non-perturbative Gauge-Higgs Unification on the Lattice
Meeting room 1, Kenkyu honkan 1F Gauge-Higgs Unification models are theories where the Higgs field is identified with some of the extra-dimensional components of the gauge field.
Gauge-Higgs Unification models are theories where the Higgs field is identified with some of the extra-dimensional components of the gauge field.
One motivation for these models is that the extra-dimensional gauge symmetry protects the Higgs potential from divergences in the ultra-violet cut-off.
Perturbative studies indicate that fermions are necessary to trigger the Higgs mechanism. Given the non-renormalizability of gauge theories in dimensions higher than four, we study non-perturbatively the simplest model which is a five-dimensional SU(2) gauge theory on a orbifold.
The starting point is the formulation on an anisotropic Euclidean lattice.
Results using a semi-analytic mean-field expansion and Monte Carlo simulations show that the Higgs mechanism takes place without fermions and support an alternative view of the lattice orbifold as a five-dimensional bosonic superconductor.
Tsunehide Kuroki, Nagoya U
SUSY breaking by nonperturbative dynamics in a matrix model for 2D type IIA superstrings
Seminar room, Kenkyu honkan 3F
We explicitly compute nonperturbative effects in a supersymmetric double-well matrix model corresponding to two-dimensional type IIA superstring theory on a nontrivial Ramond-Ramond background. We analytically determine the full one-instanton contribution to the free energy and one-point function, including all perturbative fluctuations around the one-instanton background. The leading order two-instanton contribution is determined as well. We see that supersymmetry is spontaneously broken by instantons, and that the breaking persists after taking a double scaling limit which realizes the type IIA theory from the matrix model. The result implies that spontaneous supersymmetry breaking occurs by nonperturbative dynamics in the target space of the IIA theory. We also discuss recent progress in summing up all instanton contributions using knowledge of random matrix theory
Masakiyo Kitazawa, Osaka U
Thermal fluctuations in relativistic heavy ion collisions
Seminar room, Kenkyu honkan 3F
Event-by-event fluctuations of conserved charges in relativistic heavy ion collisions are useful observables to investigate primordial thermodynamics of the hot medium generated by the collisions. In particular, they are promising observables to investigate the global structure of QCD phase diagram in experiments, and have been actively measured in the beam-energy scan program at RHIC. In this talk, I will give a review on the present status of the experimental measurement of the fluctuations observables. I will also explian why the fluctuations are interesting and important observables. Some new methods to use these observables more efficiently will also be discussed.
Philipp Gubler, RIKEN
How does the measurement of the phi-meson mass shift in nuclear matter constrain the strangeness content of the nucleon?
Seminar room, Kenkyu honkan 3F In this seminar, I will present our latest results of our study on the behavior of the phi-meson at finite density [1], which makes use of a QCD sum rule approach in combination with the maximum entropy method [2]. As earlier works have already shown, we find a strong correlation between a possible mass shift of the phi-meson in nuclear matter and the strangeness content of the nucleon, which is proportional to the strange sigma term, sigma_{sN}. In contrast to other studies, we however find that, depending on the value of sigma_{sN}, the phi-meson could receive both a positive or negative mass shift at nuclear matter density. I will discuss the relevance of our results for the interpretation of the E325 experiment, which was performed at KEK and for the future E16 experiment to be carried out at the J-PARC facility.
In this seminar, I will present our latest results of our study on the behavior of the phi-meson at finite density [1], which makes use of a QCD sum rule approach in combination with the maximum entropy method [2]. As earlier works have already shown, we find a strong correlation between a possible mass shift of the phi-meson in nuclear matter and the strangeness content of the nucleon, which is proportional to the strange sigma term, sigma_{sN}. In contrast to other studies, we however find that, depending on the value of sigma_{sN}, the phi-meson could receive both a positive or negative mass shift at nuclear matter density. I will discuss the relevance of our results for the interpretation of the E325 experiment, which was performed at KEK and for the future E16 experiment to be carried out at the J-PARC facility.
If time allows, I will also briefly describe a few possible other applications of our method, such as investigating the behavior of in hadrons in a magnetic field or the study of some basic properties of the unitary fermi gas.
[1] P. Gubler and K. Ohtani, arXiv:1404.7701 [hep-ph].
[2] P. Gubler and M. Oka, Prog. Theor. Phys. 124, 995 (2010), arXiv:1005.2459 [hep-ph].
Roberto Emparan, University of Barcelona, YITP
The large D limit of General Relativity
Meeting room 1, Kenkyu honkan 1F
General Relativity is an old theory but its dynamics remains difficult to solve and understand, in particular when strongly-gravitating objects such as black holes are involved. Although at first sight it may seem an odd idea, I will argue that it is actually quite natural to investigate the properties of this theory and its black holes in the limit in which the number of spacetime dimensions D grows to infinity. The gravitational field localizes very strongly near the black hole horizons, which simplifies dramatically the description of their interactions and allows efficient calculational approaches in an expansion in 1/D. There are also hints that this limit may lead to a reformulation of the theory in terms of low-dimensional strings.
Yuji Omura, Nagoya University
Study on two-Higgs-doublet models (with gauged U(1) symmetry)
Meeting room 1, Kenkyu honkan 1F
It is well known that generic two-Higgs-doublet models (2HDMs) suffer from potentially large Higgs-mediated flavor-changing neutral current (FCNC) problem, unless additional symmetries are imposed on the Higgs fields thereby respecting the Natural Flavor Conservation Criterion (NFC) by Glashow and Weinberg. A common way to respect the NFC is to impose Z_2 symmetry which is softly broken by a dim-2 operator. Another new way is to introduce local U(1)_H Higgs flavor symmetry that distinguishes one Higgs doublet from the other. In this talk, we discuss the phenomenology in 2HDMs with not only the Z_2 but also U(1)_H symmetry. We also study dark matter (DM) physics in the Type-I inert 2HDM with local U(1)_H Higgs gauge symmetry. The lightest neutral scalar component H of the U(1)_H-charged Higgs doublet, which does not have Yukawa couplings with the Standard-Model (SM) fermions, is stable because of the remnant discrete symmetry, and it interacts with the SM particles through the U(1)_H gauge boson (Z_H) exchange as well as the SM boson exchange. We investigate the constraints on DM: thermal relic density, and direct/indirect detections. The additional U(1)_H gauge interaction plays a crucial role in reducing the DM thermal relic density. The most important result within the inert DM model with local U(1)_H symmetry is that ~ O(10) GeV dark matter scenario, which is strongly disfavored in the usual Inert Doublet Model (IDM) with Z_2 symmetry, is revived in our model because of newly open channels, H H -> Z_H Z_H , Z_H Z. Exotic Higgs decays, h -> Z_H Z_H, Z Z_H, would be distinctive signatures of the inert 2HDM with local U(1)_H symmetry. I also give a comment on the type-II 2HDM inspired by E_6 GUT, and introduce some results on DM physics.
飯沼昌隆, 広島大学
非可換な偏光物理量の連続測定
Seminar room, Kenkyu honkan 3F
1988年にAharonovらによって提案された弱測定は、通常の量子測定とは異なり、状態をほぼ壊さずに測定する量子測定法である。初期状態をほぼ壊さずに情報を得られるため、これまで測定不可能とされた重ね合わせ状態などの中間状態での測定や、運動量と位置のような非可換な関係にある複数の物理量の連続測定を可能にする。これらの弱測定は、近年の量子測定技術の進展とともに従来では思考実験であった量子パラドックスの実験を可能しただけでなく、多くの場合、確率が負や複素数となる結果をもたらす。さらにこのとき弱測定で得られる実験値、すなわち弱値は、測定物理量の固有値の範囲を超えて大きく増大する。弱測定がもたらすこのような奇妙な結果は、従来の延長線上では考えにくいものであった。しかし近年行った偏光物理量の連続測定実験について、量子力学の数式に頼らず通常の確率論と統計的手法のみを使って、実験データから測定前の確率分布を推定したところ、量子力学や弱測定で予想される確率分布（Kirkwood-Dirac分布関数）と見事に一致した。この結果から弱値は直接得られない測定前の確率分布の平均値を表していること、測定前と測定後の確率分布は基本的に異なること、負や複素数の確率分布が本来の量子系の統計的性質である可能性が高いこと、さらに弱測定はその特性を見るきっかけを与えてくれたこと、などが分かってきた。これらは非可換な二つの偏光物理量の連続測定において初段の測定の強さを弱い領域だけでなく強い領域に至るまで行った測定からの帰結であり、量子状態は負や複素数の値を含む拡張された確率分布で記述できることを示唆する結果である。さらにこの確率分布は直接測定はできないが、その意味では密度行列と同じであり、しかも完全に１対１で対応している。セミナーでは、偏光を使った弱測定実験の結果と測定の強さの弱い領域から強い領域まで測定した連続測定実験の結果を紹介し、独立な両者の実験結果から上記の解釈ができる根拠を示す。
Yuan Qiang, IHEP
Millisecond pulsar interpretation of the Galactic center gamma-ray excess
Meeting room 2, Kenkyu honkan 1F
It was found in the Fermi-LAT data that there is an extended $gamma$-ray excess in the Galactic center region. The proposed sources to be responsible for the excess include the dark matter annihilation or an astrophysical alternative from a population of millisecond pulsars (MSPs). Whether or not the MSP scenario can explain the data self-consistently has very important implications for the detection of particle dark matter, which is however, subject to debate in the literature. In this work we study the MSP scenario in detail, based on the detected properties of the MSPs by Fermi-LAT. We build a model of the Milky Way MSPs which can reproduce the $gamma$-ray properties of the Fermi-LAT MSPs, and derive the intrinsic luminosity function of the MSPs. The model is then applied to a bulge population of MSPs. We find that the extended $gamma$-ray excess can be well explained by the bulge MSPs without violating the detectable flux distribution of MSPs by Fermi-LAT. The spatial distribution of the bulge MSPs as implied by the distribution of low mass X-ray binaries follows a $r^{-2.4}$ profile, which is also consistent with the $gamma$-ray excess data. We conclude that the MSP model can explain the Galactic center $gamma$-ray excess self-consistently, satisfying all the current observational constraints.
Yuta Hamada, Kyoto University
Naturalness and maximum entropy principle
Meeting room 3, Kenkyu honkan 1F
