Supersymmetry protects the primordial baryon asymmetry

Abstract

It has been argued that any primordial B+ L asymmetry existing at very high temperatures can be subsequently erased by anomalous electroweak effects. We argue that this is not necessarily the case in the supersymmetric standard model because, apart from B and/or L, there are, above a certain temperature T ss , two other anomalous U(1) currents. As a consequence, anomalous electroweak effects are only able to partially transform a B+ L excess into a generation of primordial sparticle (e.g. gaugino) density. This relaxes recent bounds on B-, L-violating non-renormalizable couplings by several orders of magnitude. In particular, dimension-5 couplings inducing neutrino masses may be four orders of magnitude larger than in the non-supersymmetric case, allowing for neutrino masses m v ⩽ 10 eV. These values are consistent with a MSW+see-saw explanation of the solar-neutrino data and also with possible ν μ ↔ ν τ oscillations measurable at accelerators. Cosmological bounds on other rare processes, such as neutron-antineutron oscillations get also relaxed by several orders of magnitude compared with previous estimates.