The Baryogenesis Window in the MSSM
Marcela Carena, Germano Nardini, Mariano Quiros, Carlos E. M. Wagner
TL;DR
This paper analyzes electroweak baryogenesis within the MSSM, focusing on a light stop scenario where a strong first-order electroweak phase transition can occur while satisfying experimental Higgs-mass bounds. Using RG-improved Higgs- and stop-potentials and dominant two-loop finite-temperature corrections, the authors map out a narrowly allowed region in the $(m_{\\tilde t}, m_H)$ plane, with absolute upper bounds $m_H \\lesssim 127$ GeV and $m_{\\tilde t} \\lesssim 120$ GeV. They classify cosmological histories of the EW phase transition, finding that only metastable EW vacua can realize EWBG under current constraints, provided the nucleation dynamics favor electroweak bubbles and the vacuum lifetime exceeds the age of the Universe. The work also discusses EDM constraints and indicates that the resulting parameter space should be probed by the LHC.
Abstract
Electroweak baryogenesis provides an attractive explanation of the origin of the matter-antimatter asymmetry that relies on physics at the weak scale and thus it is testable at present and near future high-energy physics experiments. Although this scenario may not be realized within the Standard Model, it can be accommodated within the MSSM provided there are new CP-violating phases and the lightest stop mass is smaller than the top-quark mass. In this work we provide an evaluation of the values of the stop (m_{\tilde t}) and Higgs (m_H) masses consistent with the requirements of electroweak baryogenesis based on an analysis that makes use of the renormalization group improved Higgs and stop potentials, and including the dominant two-loop effects at high temperature. We find an allowed window in the (m_{\tilde t},m_H)-plane, consistent with all present experimental data, where there is a strongly first-order electroweak phase transition and where the electroweak vacuum is metastable but sufficiently long-lived. In particular we obtain absolute upper bounds on the Higgs and stop masses, m_H\lesssim 127 GeV and m_{\tilde t}\lesssim 120 GeV, implying that this scenario will be probed at the LHC.