The origin of the matter-antimatter asymmetry

TL;DR

This work surveys canonical and modern mechanisms for generating the matter-antimatter asymmetry, arguing that Planck-scale and Standard Model electroweak baryogenesis are unlikely, while supersymmetric and leptogenesis pathways remain plausible. It highlights the Affleck-Dine mechanism, where coherent scalar fields along flat directions generate baryon number and can fragment into Q-balls, potentially linking ordinary matter with dark matter. By weaving together cosmology (inflation and reheating) and particle physics (neutrino masses, CP violation, SUSY breaking), the paper discusses experimental tests at colliders and dark matter searches that could validate or constrain these scenarios. The analysis suggests that detecting SUSY particles or stable Q-ball dark matter would strongly support Affleck-Dine baryogenesis and sharpen our understanding of the origin of the baryon asymmetry.

Abstract

Although the origin of matter-antimatter asymmetry remains unknown, continuing advances in theory and improved experimental limits have ruled out some scenarios for baryogenesis, for example the sphaleron baryogenesis at the electroweak phase transition in the standard model. At the same time, the success of cosmological inflation and the prospects for discovering supersymmetry at the LHC have put some other models in sharper focus. We review the current state of our understanding of baryogenesis with the emphasis on those scenarios that we consider most plausible.

Figures (9)

• Figure 1: Interference between the tree-level (a) and one-loop (b) diagrams with complex Yukawa couplings can provide the requisite source of CP violation for GUT baryogenesis. In viable models, to avoid the unwanted cancellations, one must often assume that the two scalars are different or go to higher loops (c) barrkolb.
• Figure 2: Schematic Yang-Mills vacuum structure. At zero temperature, the instanton transitions between vacua with different Chern-Simons numbers are suppressed. At finite temperature, these transitions can proceed via sphalerons.
• Figure 3: First and second order phase transitions.
• Figure 4: Results of two independent calculations of baryon asymmetry in the MSSM. On the left, contours of constant baryon asymmetry in units $10^{-10}$ calculated by cjk for the bubble wall velocity $v_{\rm w} = 0.03$ and $\tan \beta \stackrel{<}{ \sim} 3$. Mass units are GeV. Shaded regions are excluded by the LEP2 limit on the chargino mass, $m_{\chi^\pm}>104$ GeV. To maximize the baryon asymmetry, one assumes that the bubble wall is very narrow, $\ell_w \simeq 6/T$, and its velocity is $v_w=0.03$. The plot on the right represents the results of carena_2002 for $\tan \beta =10$ and a maximal CP violating phase of the $\mu$ parameter. The other parameters in both calculations have been chosen to maximize the resulting baryon asymmetry. Also shown is the observed value of the baryon asymmetry reported by WMAP map, $\eta=6.1{\,}^{+0.3}_{-0.2}$.
• Figure 5: The charge density per comoving volume in (1+1) dimensions for a sample potential analyzed numerically during the period when the spatially homogeneous condensate breaks up into high- and low-density domains. Two domains with high charge density are expected to form Q-balls.