Yusuke Kimura, YITP, Kyoto University
Discrete Gauge Symmetries in F-theory Compactifications without Section (in Japanese)
Meeting room 3, Kenkyu honkan 1F
セクションを持たないF理論のモデルを考察する。セクションを持たないF理論のモデルにおいては、離散ゲージ群が自然に現れ。セクションを持たないF理論のモデルの構成や、現れる離散ゲージ群について議論する。射影空間の積における超曲面や完全交叉、および射影空間の積の２重被覆を考えることで、genus-1ファイバーを持ったセクションのないカラビ・ヤウ4-foldsを構成する。Jacobian fibrationsやそのMordell-Weil群についても議論する。また、7ブレーン上の非可換ゲージ対称性についても議論する。
Richard Ruiz, Durham U., IPPP
Neutrino Jets from High-Mass WR Gauge Bosons in TeV-Scale Left-Right Symmetric Models
Meeting room 1, Kenkyu honkan 1F, In this seminar, we re-examine the discovery potential at hadron colliders of high-mass WR gauge bosons in Left-Right Symmetric Models. We focus on the case where the WR is very heavy compared to the heavy Majorana neutrino N. Present search strategies for WR-N production are not sensitive to this regime due to the breakdown of the collider signature definition: since the neutrinos produced in WR decays are highly boosted, their decays to leptons and jets are highly collimated, forming a single object we call a “neutrino jet.”
In this seminar, we re-examine the discovery potential at hadron colliders of high-mass WR gauge bosons in Left-Right Symmetric Models. We focus on the case where the WR is very heavy compared to the heavy Majorana neutrino N. Present search strategies for WR-N production are not sensitive to this regime due to the breakdown of the collider signature definition: since the neutrinos produced in WR decays are highly boosted, their decays to leptons and jets are highly collimated, forming a single object we call a “neutrino jet.”
After exploring the phenomenology of neutrino jets, we consider an alternative WR-N search strategy at hadron colliders. We include QCD corrections to WR production with threshold resummation at NNLL and matched, for the first time, to the threshold-improved parton distributions. We these improvements, we present the discovery potential of neutrino jets at the 13 TeV Large Hadron Collider and a hypothetical future 100 TeV Very Large Hadron Collider.
(references)
1607.03504, 1610.08985
Natsumi Nagata, The University of Tokyo
A supersymmetric two-field relaxion model
Meeting room 1, Kenkyu honkan 1F
We discuss a supersymmetric version of a two-field relaxion model that naturalizes supersymmetric models with high SUSY-breaking. This exploits a relaxion mechanism that does not depend on QCD dynamics and where the relaxion potential barrier height is controlled by a second axion-like field. During the cosmological evolution, the relaxion rolls down with a nonzero value that breaks supersymmetry and scans the soft supersymmetric mass terms. Electroweak symmetry is broken after the soft masses become of order the supersymmetric Higgs mass term and causes the relaxion to stop rolling. This can explain the tuning in supersymmetric models, while preserving the QCD axion solution to the strong CP problem. We will also consider possible inflation models compatible with this framework.
Olcyr Sumensari, LPT Orsay
B-Physics Puzzles and Lepton Flavor Violation
Meeting room 1, Kenkyu honkan 1F
Even though the LHC searches so far did not unveil the new physics (NP)particles, the B-physics experiments at LHCb, BaBar and Belle hint towards deviations from Lepton Flavor Universality in semi-leptonic decays. In this talk I will review the status of these puzzles, and discuss the possibilities for BSM scenarios. Particular emphasis will be given to the implications for Lepton Flavor Violation in B meson decays
Mayumi Saitou, Ochanomizu University
Hydrodynamics on non-commutative space
Meeting room 3, Kenkyu honkan 1F Recently, Y. Nambu formulated a new hydrodynamics in which incompressible fluid dynamics is connected to Hamiltonian dynamics in terms of area preserving diffeomorphism. If the equations of motion of two-dimensional fluid are expressed using Poisson brackets, then it is allowed to understand a stream function plays a role of Hamiltonian. According to this standpoint, three-dimensional incompressible fluid theory can be related to the dynamics of Nambu brackets.
Recently, Y. Nambu formulated a new hydrodynamics in which incompressible fluid dynamics is connected to Hamiltonian dynamics in terms of area preserving diffeomorphism. If the equations of motion of two-dimensional fluid are expressed using Poisson brackets, then it is allowed to understand a stream function plays a role of Hamiltonian. According to this standpoint, three-dimensional incompressible fluid theory can be related to the dynamics of Nambu brackets.
In this talk, we investigate a hydrodynamics on non-commutative space based on the formulation of dynamics by Nambu. Replacing Poisson or Nambu brackets by Moyal brackets with a parameter θ, a new hydrodynamics on non-commutative space is derived. It has an additional term of O(θ2), which does not exist in the usual Navier-Stokes equation.
In hydrodynamics, to introduce Moyal brackets corresponds to a kind of quantization procedure regarding position coordinates x and y, so that it makes the position coordinates to non-commutative ones. This procedure may be a step toward finding the hydrodynamics of granular materials whose minimum size is given by θ. In order to examine the non-commutative effect, I compare the behaver of flows which have different size of θ by computer simulation. In all the discussions in this talk, incompressibility and non-relativistic flow are supposed.
Keisuke Izumi, Nagoya University
Causal Structures in Gauss-Bonnet gravity
Meeting room 3, Kenkyu honkan 1F The couplings with curvature in kinetic terms would arise as corrections from the quantum gravity theory, such as string theory. The curvature coupling in general makes the propagation to be superluminal. In the theory with superluminal modes, the causal analysis with null curves is meaningless, and thus the causal structures are nontrivial. Especially, we have to define black holes based on the fastest propagation.
The couplings with curvature in kinetic terms would arise as corrections from the quantum gravity theory, such as string theory. The curvature coupling in general makes the propagation to be superluminal. In the theory with superluminal modes, the causal analysis with null curves is meaningless, and thus the causal structures are nontrivial. Especially, we have to define black holes based on the fastest propagation.
In this talk, Gauss-Bonnet gravity will be discussed as the simplest model. We could say that in this model the kinetic term of graviton has the coupling with curvature. This model has the superluminal modes of graviton. However, we show the theorem; in stationary spacetimes, “horizon” defined by the null curve (i.e. in the usual way) becomes exactly the causal edge (i.e. the horizon in the sense of causality). Meanwhile, in dynamical spacetimes, the causal edge does not coincide with the “horizon” defined by null curves. Especially, in shrinking black hole spacetimes (by Hawking radiation), the gravitons can escape from the inside of “BH” defined by null curves.
Reference: K. Izumi, Phys.Rev. D90 (2014) no.4, 044037
Simona Murgia, University of California, Irvine
Searching for Dark Matter Shining in Gamma Rays
Seminar room, Kenkyu honkan 3F The center of the Milky Way is predicted to be the brightest source of gamma rays produced bydark matter annihilation or decay. In recent years, claims have been made of an excess consistent with a dark matter annihilation signal in the data collected by the Fermi Large Area Telescope towards the Galactic center.
The center of the Milky Way is predicted to be the brightest source of gamma rays produced bydark matter annihilation or decay. In recent years, claims have been made of an excess consistent with a dark matter annihilation signal in the data collected by the Fermi Large Area Telescope towards the Galactic center.
Although these results are intriguing, the complexity involved in modeling the foreground and background emission from conventional astrophysical sources of gamma rays makes a conclusive interpretation of these results challenging.
In this talk, I’ll present results from these searches.
Tim Tait, University of California, Irvine
Evidence for a 17 MeV Boson from Rare Excited 8Be Decays?
Meeting room 3, Kenkyu honkan 1F
I will discuss the recent experimental results from the ATOMKI group which measured the spectrum ofinternal pair conversion e+e- events in the decay of an excited state of beryllium-8 to its ground state. They observe a resonant-like structure in the invariant mass of the e+e- which is suggestiveof a new boson at 17 MeV. I’ll review the experimental results and the types of theories whichcan describe them.
Takashi Toma, Laboratoire de Physique Theorique d'Orsay
Electric Dipole Moments of Charged Leptons with Sterile Fermions
Seminar room, Kenkyu honkan 3F
We address the impact of sterile fermions on charged lepton electric dipole moments. In this work, we consider a minimal extension of the Standard Model via the addition of sterile fermions which mix with active neutrinos. Our study reveals that, in order to have a non-vanishing contribution in this framework, the minimal extension necessitates the addition of at least 2 sterile fermion states. Sterile neutrinos can give significant contributions to the charged lepton electric dipole moments if the masses of the non-degenerate sterile states are both above the electroweak scale. In addition, the Majorana nature of neutrinos is also important for the charged lepton electric dipole moments. Furthermore as a more concrete model, we consider the most minimal realisation of the Inverse Seesaw mechanism, in which the Standard Model is extended by two right-handed neutrinos and two sterile fermion states. Our study shows that the two pairs of (heavy) pseudo-Dirac mass eigenstates can give significant contributions to the electron electric dipole moment, lying close to future experimental sensitivity. In our analysis we further discuss the possibility of having a successful leptogenesis in this framework, compatible with a large electron electric dipole moment.
Masahiro Hotta, Tohoku University
Gravitational Memory Charges of Supertranslation and Superrotation on Rindler Horizons
Meeting room 1, kenkyu honkan 1F
