arXiv:2607.02026·v2·High Energy Physics — Phenomenology

One-loop proton decay from Peccei-Quinn symmetry

Abstract

We promote the accidental $B + L$ symmetry of the Standard Model to a Peccei-Quinn (PQ) symmetry while realizing spontaneous proton decay radiatively. The PQ anomaly sector consists of vector-like quarks (VLQs), providing a Kim-Shifman-Vainshtein-Zakharov-type axion solution to the strong CP problem. After spontaneous PQ breaking, a residual $Z_{2}$ symmetry remains, which forbids tree-level proton decay. The VLQs required to generate the QCD anomaly, together with scalar mediators, odd under the residual $Z_{2}$ , induce one-loop proton decay through the effective operator $u_{R} u_{R} d_{R} e_{R}$ . We study its ultraviolet completions, featuring distinct vector-like fermion and scalar representations, and show that the resulting models lead to distinct predictions for the axion-to-photon coupling, testable in helioscope and haloscope experiments. We investigate proton and neutron decay pheneomenology focusing on the channel $p \to e^{+} π^{0}$ . We also discuss axion dark matter in pre- and post-inflationary cosmology.

Comments: 17 LaTeX pages; 3 figures. Minor changes in main text, Fig.3 updated with new plot added and references added. Matches version published in PLB