Understanding and predicting low-energy neutrino parameters with leptogenesis

Abstract

In this work, we address two major problems of the Standard Model of particle physics: the baryon asymmetry of the Universe and neutrino masses and mixing. A strict link between these two aspects can be established by the seesaw mechanism and leptogenesis. This connection can be fruitfully exploited to gain information on neutrino parameters. To this aim, we first introduce the type-I seesaw mechanism and leptogenesis, moving then to the strong thermal leptogenesis scenario. Here a large pre-existing asymmetry is efficiently erased by leptogenesis, and an analytical lower bound on the absolute neutrino mass scale can be derived. We then consider SO(10)-inspired leptogenesis, in which a set of conditions kindred to those realised in SO(10) Grand Unification Theories is imposed on the seesaw setup. A rigorous analytical study of this scenario is performed, allowing us to obtain analytical explanations of the numerous predictions on neutrino parameters. SO(10)-inspired and strong thermal SO(10)-inspired leptogenesis appear then to represent a very interesting scenario, rich of definite predictions on neutrino parameters that will be in the reach of forthcoming experiments. Finally, we examine the supersymmetric extension of SO(10)-inspired leptogenesis, analysing how the constraints on neutrino parameters change. The lower bound imposed by thermal leptogenesis on the reheating temperature is carefully studied, in light of the gravitino problem. We conclude that the thermal leptogenesis scenario represents an intriguing and viable mechanism also in the supersymmetric framework.

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