BAU production in the $S_N$-breaking Standard Model

TL;DR

This paper investigates how breaking $S_N$ symmetries in the Standard Model can generate sufficient CP violation to explain the universe's baryon asymmetry, showing that existing models are already capable of this without new issues.

Contribution

It demonstrates that $S_N$-breaking in the Standard Model can produce enough CP violation to account for the baryon asymmetry of the universe, using numerical analysis of parameter variations.

Findings

CP violation can be significantly enhanced near specific parameter values.

$S_N$-breaking models can generate sufficient baryon asymmetry.

Numerical results show regions with $R_{ riangle} > 10^{10}$.

Abstract

CP violation (CPV) and the baryon asymmetry of the universe (BAU) are two of the most significant unresolved problems in physics. This article presents further research on the CPV problem in the standard model (SM) with thirty-two candidate sets of the ten "natural" parameters that exhibit the same CKM performance. These parameters are considered "natural" because they consist solely of the Yukawa couplings and the vacuum expectation value (VEV) of the unique Higgs doublet in the SM. We then investigate the CPV problem and the BAU problem using the Jarlskog measure of CPV, $\Delta_{CP}=J(m^2_t -m^2_c)(m^2_t -m^2_u)(m^2_c -m^2_u)(m^2_b -m^2_s)(m^2_b -m^2_d)(m^2_s -m^2_d)/ T^{12}$, given that CP symmetry is violated following the breakdowns of $S_N$ symmetries. Subsequently, we perform numerical tests in a simplified scenario where eight of the ten parameters are fixed, and the remaining two parameters are allowed to vary from their $S_2$-symmetric values ${\bf (x,~y)}=(-1,~1)$ to their current values in all thirty-two parameter sets. To estimate the enhancement of CPV in such processes, we propose a ratio $R_{\Delta} \equiv \Delta_{CP} / \Delta^{(0)}_{CP}$ between the running $\Delta_{CP}$ and its current value, denoted by $\Delta^{(0)}_{CP}$, which is approximately $10^{-20}$. In all thirty-two cases, the three-dimensional (3D) plots of $R_{\Delta}$ exhibit many regions that stick out of the $R_{\Delta}=10^{10}$ plane, especially in regions very close to ${\bf (x,~y)}=(-1,~1)$. These results demonstrate that the $S_N$-breaking Standard Model is already sufficient to violate CP symmetry explicitly and generate a significant amount of BAU. Furthermore, it solves existing problems without creating new ones.