Moderately Suppressed Dimension-five Proton Decay in a Flipped $SU(5)$ Model

TL;DR

This paper analyzes how a flipped SU(5) GUT model moderates dimension-five proton decay, balancing observable decay rates with suppression to meet experimental bounds, through specific Higgsino and GUT-scale mass structures.

Contribution

It introduces a flipped SU(5) model with a unique Higgsino mass structure that moderates proton decay rates while maintaining observable decay signatures.

Findings

Moderate suppression of proton decay consistent with current bounds.

Predicted distributions of proton decay mode ratios.

Quantitative evaluation of Wilson coefficients related to decay modes.

Abstract

We study colored Higgsino-mediated proton decay (dimension-five proton decay) in a model based on the flipped $SU(5)$ GUT. In the model, the GUT-breaking ${\bf10}$, ${\bf \overline{10}}$ fields have a GUT-scale mass term and gain VEVs through higher-dimensional operators, which induces an effective mass term between the color triplets in the ${\bf 5}$, ${\bf \bar{5}}$ Higgs fields that is not much smaller than the GUT scale. This model structure gives rise to observable dimension-five proton decay, and at the same time achieves moderate suppression on dimension-five proton decay that softens the tension with the current bound on $\Gamma(p\to K^+\nu)$. We investigate the flavor dependence of the Wilson coefficients of the operators relevant to dimension-five proton decay, by relating them with diagonalized Yukawa couplings and CKM matrix components in MSSM, utilizing the fact that the GUT Yukawa couplings are in one-to-one correspondence with the MSSM Yukawa couplings in flipped models. Then we numerically evaluate the Wilson coefficients, and predict the distributions of the ratios of the partial widths of various proton decay modes.