5. Theoretical Physics (CSN4)

Matter-Antimatter Asymmetry from Soft Supersymmetry Breaking

by Dr Fong Chee Sheng

Aula A1 (LNF)

Aula A1


Via Enrico Fermi, 40 00044 Frascati (Roma)
The fact that we live in a matter-antimatter asymmetric universe is a deep mystery in which the Standard Model (SM) of particle physics falls short of explaining. Imposing supersymmetry (SUSY) on the SM plus right-handed neutrinos with large lepton-number-violating Majorana masses results in the stability of Higgs mass under quantum corrections, the small active neutrino masses and the generation of baryon asymmetry of the universe (baryogenesis) through leptogenesis. However we know that SUSY has to be broken and the existence of the soft SUSY-breaking terms introduce additional CP-violating sources which can be utilized in leptogenesis in a scenario termed Soft Leptogenesis (SL). First, we study the CP violation in SL and show that for all soft SUSY-breaking sources of CP violation an exact cancellation between the leading order asymmetries produced in the fermionic and bosonic channels occurs at T=0. Hence thermal effects have to be taken into account to partially lift this cancellation. Then we discuss the effective theory appropriate for studying SL. In the temperature range relevant for SL lepton flavor effects play an important role and in particular they could enhance the efficiency of SL by up to a factor of 1000 from the unflavored scenario, permitting larger values of the required lepton-number-violating soft bilinear term up to a natural SUSY scale (TeV). Interestingly at temperatures T > 10^7 GeV the main source of B-L asymmetry is the CP asymmetry of a new anomalous R-charge. This results in baryogenesis through R-genesis with an efficiency that can be up to two orders of magnitude larger than in the usual estimates. Contrary to common belief, in this regime, a sizeable baryon asymmetry is generated also when thermal effects are neglected