报告题目: Detecting High-Frequency Gravitational Waves in Planetary Magnetosphere
报告人: Dr.Takumi Kuwahara（Peking University）
报告日期: 2：00-3：00 PM, Jun.23, 2025
报告地点: 理8栋学术报告厅118
摘要：
Composite asymmetric dark matter (ADM) is the framework that naturally explains the coincidence of the baryon density and the dark matter density of the Universe. We introduce a portal interaction sharing particle-antiparticle asymmetries in the Standard Model and dark sectors. A dark photon mixing with our photon is also introduced as a low-energy portal interaction for the entropy transfer at the late-time of the Universe. These portal interactions play important roles in exploring the dark sector in this model. The dark hadrons are produced via the dark photon at the collider experiments and leave the visible decay signals. In particular, for a specific mass spectrum, we can explore the composite ADM at the long-lived particle searches at the forward-detector experiments such as FASER and FACET and the beam-dump experiments such as Dark Quest. The kinetic mixing of order of 10^-3 — 10^-5 can be explored by the forward-detector experiments on the long-lived dark hadrons, which is compatible with the direct searches of visible decay of dark photon. Through the portal interaction sharing particle-antiparticle asymmetries, dark matter particles, which are dark-sector counterparts of baryons, can decay into antineutrinos and dark-sector counterparts of mesons (dark mesons) or dark photon. Subsequent cascade decays of the dark mesons and the dark photon can also provide electromagnetic fluxes at late times of the Universe. We derive constraints on the timescale of dark matter decay in the composite ADM scenario from the astrophysical observations of the positron, electron, and gamma-ray fluxes. The constraints from cosmic-ray positron measurements by AMS-02 are the most stringent at 2 GeV: a lifetime should be larger than the order of 10^{26} s, corresponding to the cutoff scale of the portal interaction of about 10^8—10^9 GeV.
报告人简介：
Takumi Kuwahara is a postdoctoral fellow at Peking University, Center for High Energy Physics. He obtained his PhD degree in 2017 from Nagoya University. He worked as a postdoctoral fellow at University of Tokyo and institute for basic science (Republic of Korea) before joining CHEP, PKU. His main research interests focus on particle physics, in particular, dark matter and dark sector physics.