Proton decay via dimension-six operators in intersecting D6-brane models

TL;DR

The paper investigates proton decay in supersymmetric $SU(5)$ GUTs realized via intersecting D6-branes in Type IIA orientifolds, focusing on dimension-six operators. It develops explicit vertex operators for massless states at D-brane intersections and computes two four-fermion string amplitudes, including both gauge-boson- and Higgs-mediated contributions, with normalization fixed by gauge-boson exchange. When mapped to four-dimensional field theory quantities, the string effects yield a modest enhancement of the proton decay rate, giving a lifetime around $\tau_p^{ST} \sim (0.5-2.1)\times 10^{36}$ years under plausible parameters. The results, together with the explicit vertex-operator toolkit, clarify the stringy corrections to proton decay in local intersecting-brane GUTs and quantify their phenomenological impact.

Abstract

We analyze the proton decay via dimension six operators in supersymmetric SU(5)-Grand Unified models based on intersecting D6-brane constructions in Type IIA string theory orientifolds. We include in addition to 10* 10 10* 10 interactions also the operators arising from 5-bar* 5-bar 10* 10 interactions. We provide a detailed construction of vertex operators for any massless string excitation arising for arbitrary intersecting D-brane configurations in Type IIA toroidal orientifolds. In particular, we provide explicit string vertex operators for the 10 and 5-bar chiral superfields and calculate explicitly the string theory correlation functions for above operators. In the analysis we chose the most symmetric configurations in order to maximize proton decay rates for the above dimension six operators and we obtain a small enhancement relative to the field theory result. After relating the string proton decay rate to field theory computations the string contribution to the proton lifetime is tau^{ST}_p =(0.5-2.1) x 10^{36} years, which could be up to a factor of three shorter than that predicted in field theory.

Figures (2)

• Figure 1: Intersection angles for the case $-\frac{1}{2}<\theta_{1}<0 , -\frac{1}{2}<\theta_{2}<0, \frac{1}{2}<\theta_{3}<1$.
• Figure 2: Intersection angles for the case $\frac{1}{2}<\theta_{1}<1, \frac{1}{2}<\theta_{2}<1, \frac{1}{2}<\theta_{3}<1$