SO(10)-inspired solution to the problem of the initial conditions in leptogenesis

Abstract

We show that, within SO(10)-inspired leptogenesis, there exists a solution, with definite constraints on low energy neutrino parameters, able simultaneously to reproduce the observed baryon asymmetry and to satisfy the conditions for the independence of the final asymmetry of the initial conditions (strong thermal leptogenesis). We find that the wash-out of a pre-existing asymmetry as large as O(0.1) requires: i) reactor mixing angle in the range \theta_13 = (2 - 20) degrees, in agreement with the experimental result \theta_13 = (8 - 10) degrees; ii) atmospheric mixing angle in the range \theta_23 = (16 - 41) degrees, compatible only with current lowest experimentally allowed values; iii) Dirac phase in the range \delta \simeq -\pi/2 - \pi/5, with the bulk of the solutions around \delta \simeq -\pi/5 and such that sign(J_CP)= - sign(\eta_B); iv) neutrino masses m_i normally ordered; v) lightest neutrino mass in the range m_1 \simeq (15 - 25) meV, corresponding to \sum_i m_i \simeq (85 - 105) meV; vi) neutrinoless double beta decay (0\nu\beta\beta) effective neutrino mass m_ee \simeq 0.8 m_1. All together this set of predictive constraints characterises the solution quite distinctively, representing a difficultly forgeable, fully testable, signature. In particular, the condition m_ee \simeq 0.8 m_1 \simeq 15 meV can be tested by cosmological observations and (ultimately) by 0\nu\beta\beta experiments. We also discuss different aspects such as theoretical uncertainties, stability under variation of the involved parameters, form of the orthogonal and RH neutrino mixing matrices.