Nagoya University
Theoretical Elementary Particle Physics Laboratory

Date&Time Mon May 10 2021 (14:00 - 15:00)
Tomohiro Fujita
Affiliation Waseda Univ.
Title Hunting Axion like Particles by Observations and Experiments
Abstract Axion like particle (ALP) is a well-motivated hypothetical particle beyond the standard model and attracts growing attention. In this seminar, I discuss the possible roles of ALPs in the Universe and their experimental/observational tests. Recently, a re-analysis of Planck satellite data found the cosmic birefringence with the statistical significance of 2.4σ. This is a signal beyond the ΛCDM standard cosmology and can be explained by a slow-rolling ALP with a Chern-Simons coupling to photons which is responsible for dark energy. Alternatively, if the ALP rolls down its potential before the CMB emission, it not only explains the observed cosmic birefringence but also alleviates the Hubble tension problem. Furthermore, ALP with a tiny mass is a promising candidate for dark matter, because its extended de Broglie wave naturally resolves the core-cusp problem. We are running three independent ALP dark matter search projects in the ultra-light mass range 10^{-22}eV < m < 10^{-10}eV. I would like to introduce them, when time allows.
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