B-ball Baryogenesis and the Baryon to Dark Matter Ratio

TL;DR

This paper proposes B-ball Baryogenesis (BBB) as a natural mechanism within the MSSM to explain why the baryon and dark matter densities are of the same order. BBB relies on Affleck-Dine condensate dynamics that fragment into Q-balls carrying baryon number, with B-balls surviving thermalization and decaying after the LSP freeze-out to produce neutralinos, thereby linking baryon and dark matter densities via similar number densities. The analysis identifies a viable parameter window, especially for the d=6 $u^c d^c d^c$ direction, requiring a relatively low reheating temperature $T_R \sim 10^{3}$–$10^{5}$ GeV, and derives constraints from B-ball formation efficiency, thermal destruction, and LSP annihilation. The suggested scenario elegantly ties MSSM physics to cosmological observations, making concrete predictions about the allowed reheating temperatures, LSP masses (potentially $m_\chi\lesssim 67$ GeV in pure BBB), and inflationary model requirements, while favoring specific flat directions for the AD condensate.

Abstract

We demonstrate that B-ball decay in the MSSM can naturally solve the puzzle of why the densities of baryons and dark matter in the Universe are similar. This requires that the B-balls survive thermalization and decay below the freeze-out temperature of the neutralino LSP, typically 1-10GeV. It is shown that this can happen if the baryon asymmetry originates from a squark condensate along the d=6 u^{c}d^{c}d^{c} D-flat direction of the MSSM scalar potential. For this to work the reheating temperature after inflation must be no greater than 10^3-10^5 GeV.