Teppei Kitahara, KMI, Nagoya University

Direct CP violation in $K ¥to ¥mu^+ ¥mu^-$ and new physics search

##### A rare decay $K_L ¥to ¥mu^+ ¥mu^-$ has been measured precisely, while a similar rare decay $K_S ¥to ¥mu^+ ¥mu^-$ has not been seen yet, which will be measured by an upgrade of the LHCb experiment. Although both processes are almost CP conserving, I will point out that an interference contribution between $K_L$ and $K_S$ in a neutral kaon beam emerges from a genuine direct CP violation. It will be shown that the interference contribution can be a comparable size to the standard-model prediction of BR$(K_S ¥to ¥mu^+ ¥mu^-)$. I will also introduce several new physics effects in $K ¥to ¥mu^+ ¥mu^-$, and a connection with $¥epsilon’/¥epsilon$, which is a direct CP violation in $K ¥to ¥pi ¥pi$.

References:

arXiv:1707.06999, Phys.Rev.Lett. 119 (2017) 20, 201802

arXiv:1711.11030, JHEP 05 (2018) 024

arXiv:1712.04959, JHEP 04 (2018) 019

Takuya Furusawa, TITECH

[KEK-Keio-YITP-Joint seminar] Global anomaly matching in the higher-dimensional CP^N model

##### “An ‘t Hooft anomaly is an obstruction to gauge global symmetries and constrains low-energy behaviors of a system. In this talk, we focus on the 3D CP^N model, an effective field theory of quantum anti-ferromagnets, and derive a mixed ‘t Hooft anomaly between the refection and magnetic symmetries. To detect the ‘t Hooft anomaly, we insert a flux for the reflection symmetry by putting the model on a non-orientable manifold. Then, we find an obstruction to gauge the magnetic symmetry. This anomaly indicates that even when the flavor symmetry is broken explicitly, the model doesn’t admit a unique gapped ground state as long as the refection and magnetic symmetries are respected. As an application, we also discuss the finite-temperature phase diagram of the CP^N model. This talk is based on: T.F., M. Hongo, “Global anomaly matching in the higher-dimensional $¥mathbb{CP}^{N?1}$ model”, PRB. 101, 155113, (2020).”

Ryosuke Sato, DESY

Axion fragmentation and its implication for relaxion scenario

##### The axion(-like particle) is ubiquitous in physics beyond the standard model. The axion has cosine-like potential, and the axion filed goes over a large number of wiggles if its initial velocity is large enough to overcome the barrier.

During this process, the axion quantum fluctuation grows exponentially and this growth of quantum fluctuation gives friction to zeromode.

We denote this phenomenon as axion fragmentation, and discuss it in detail.

We also discuss its implication for the relaxion scenario which is a solution for the electroweak hierarchy problem.

Takahisa Igata, KEK

[cosmophys seminar] Polarization patterns on the outer edge of the black hole shadow and the gravitational Faraday rotation

##### When lights orbiting around a black hole reach an observation point, they form a photon ring that outlines the black hole shadow. In this talk, we focus on the polarization pattern on a photon ring formed by linearly polarized lights and show how it depends on the spin parameter of the black hole and the inclination angle of the rotation axis. We clarify the relationship between polarization propagation and hidden symmetry in the Kerr spacetime, such as the Killing-Yano symmetry, and consider the gravitational Faraday rotation, which is a rotation of the polarization plane due to the gravitational field during propagation.

Yu Hamada, Kyoto University

Topological Nambu monopole in two Higgs doublet models

##### Two Higgs doublet model (2HDM), in which one more Higgs doublet is added to the Standard Model(SM), is one of the most simple extensions of the SM. 2HDM allows a solitonic object called as the Nambu monopole, which is a magnetic monopole attached with two vortex strings.

We show that the monopole is topologically stable when the Higgs potential has a global U(1) symmetry and a $¥mathbb{Z}_2$ symmetry. We also discuss phenomenological implications of the monopole. This talk is based on arXiv:1904.09269 and 2003.08772.

Mitsunori Kubota, Osaka University

CP-violating Higgs model canceling the electric dipole moment

##### 5Baryon asymmetry of the Universe requires an extra CP violation and a mechanism for departure from equilibrium for a baryon-number changing process. The extended model with the CP-violating Higgs sector is a good candidate realizing it. However, such extra CP violation is strongly constrained by the electric dipole moment (EDM) data. In this talk, we propose an idea to overcome that conflict between the requirement and the constraint in the general two Higgs doublet model in which the CP-violating phases are originated by the scalar potential and the Yukawa interaction. In our scenario, the contributions to the EDM from the two sources of the CP violation can lead to destructive interference. Consequently, we show that the individual CP-violating phases can get O(1) [rad] while the EDM constraints are satisfied. This talk is based on arXiv:2004.03943 [hep-ph].

Tobias Binder, Kavli IPMU, University of Tokyo

Progress in understanding dark matter Sommerfeld-enhanced annihilation, bound-state formation and decay in the early Universe

##### If DM is realized at around the TeV-mass region or above, even the heaviest electroweak force carriers could act as long-range forces, leading to the existence of meta-stable DM bound states. The formation and subsequent decay of the latter further deplete the relic density during the freeze-out process on top of the Sommerfeld enhancement, allowing for larger DM masses. In this talk, I discuss how a dense and hot primordial plasma environment influences these quantum mechanical effects, leading to a more complete description and more precise prediction of the thermal WIMP relic abundance.

岡田崇, RIKEN

[cancelled] KEK連携コロキウム「進化ダイナミクスの数理入門」

Tobias Binder, Kavli IPMU, University of Tokyo

[cancelled] Progress in understanding dark matter Sommerfeld-enhanced annihilation, bound-state formation and decay in the early Universe

##### If DM is realized at around the TeV-mass region or above, even the heaviest electroweak force carriers could act as long-range forces, leading to the existence of meta-stable DM bound states. The formation and subsequent decay of the latter further deplete the relic density during the freeze-out process on top of the Sommerfeld enhancement, allowing for larger DM masses. In this talk, I discuss how a dense and hot primordial plasma environment influences these quantum mechanical effects, leading to a more complete description and more precise prediction of the thermal WIMP relic abundance.

Reona Arai, Tokyo Institute of Technology

[cancelled] Finite N corrections to the Schur index from D3-brane analysis in AdS_5/CFT_4