Matter-antimatter asymmetry creation in the early Universe and particle collective excitations

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K17644
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Nagoya University
• Principal Investigator: Miura Kohtaroh 名古屋大学, 基礎理論研究センター, 研究員 (50511432)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: ニュートリノ集団励起とレプトン数生成

Outline of Final Research Achievements

We have investigated a creation mechanism of matter-antimatter asymmetry observed in the Universe in terms of a collective excitation of elementary particles in the electroweak phase transition (EWPT) era. We have focused on the resonant-leptogenesis in which the lepton number would be created at around the EWPT - a frontier of the high energy particle physics, and it is thus under scrutiny with phenomenological interests. An important feature in the EWPT is that left-handed neutrinos possess a non-trivial collective excitation due to the presence of massive weak bosons. We have taken account of this effect and evaluated the decay rate of the right-handed neutrino, a key quantity in the leptogenesis. Comparing to the case assuming massless weak bosons, the decay rate gets 30% enhancement at around 100 GeV.

Free Research Field

素粒子物理学