Baryogenesis vs. proton stability in theories with extra dimensions.pdf

a r X i v : h e p - p h / 0 0 0 3 3 1 2 v 1 3 1 M a r 2 0 0 0 Baryogenesis vs. proton stability in theories with extra dimensions Antonio Masiero?, Marco Peloso?, Lorenzo Sorbo?, and Rula Tabbash§ Scuola Internazionale Superiore di Studi Avanzati (S.I.S.S.A.), Via Beirut 2? 4, I ? 34014 Trieste, Italy and Istituto Nazionale di Fisica Nucleare, Sez. di Trieste Via Valerio 2, I ? 34127 Trieste, Italy (March 31, 2000) We propose a new scenario of baryogenesis in the context of theories with large extra dimensions. The baryon number is almost conserved at zero temperature by means of a localization mechanism recently analyzed by Arkani-Hamed and Schmaltz: leptons and quarks are located at two slightly displaced positions in the extra space, and this naturally suppresses the interactions which “convert” the latter in the former. We show that this is expected to be no longer true when finite temperature effects are taken into account. The whole scenario is first presented in its generality, without referring to the bulk geometry or to the specific mechanism which may generate the baryon asymmetry. As an example, we then focus on a baryogenesis model reminiscent of GUT baryogenesis. The Sakharov out of equilibrium condition is satisfied by assuming nonthermal production of the bosons that induce baryon number violation. PACS: 98.80.Cq, 11.10.Kk Preprint : SISSA 31/2000/EP I. INTRODUCTION Despite the great success of Quantum Field Theory, a consistent scenario where gravity is also included still lacks. The most promising framework that could help in this task is string theory, whose consistency requires additional dimensions beyond the standard 3 + 1 . This extra space is usually assumed to be compact, with a small compactification radius of order M? 1p . However, it has been observed in ref. [1] that, having no test of gravity below the millimeter scale, we do not really need such a tiny compactification radius, provided the extra dimensions are accessible only to gr