Baryon number violating hydrogen decay

TL;DR

This paper investigates the decay of hydrogen atoms via baryon number violating interactions using an effective field theory approach, providing new bounds on decay widths and exploring potential astrophysical signals.

Contribution

First application of EFT to estimate hydrogen BNV decay widths using nucleon decay constraints, integrating LEFT, ChPT, and SMEFT frameworks.

Findings

Bounds on inverse partial widths exceed 10^44 years.

Diphoton decay H→γγ is least constrained and potentially astrophysically interesting.

Monochromatic photon signals from the Sun are challenging to detect.

Abstract

Most studies on baryon number violating (BNV) processes in the literature focus on free or bound nucleons in nuclei, with limited attention given to the decay of bound atoms. Given that hydrogen is the most abundant atom in the universe, it is particularly intriguing to investigate the decay of hydrogen atom as a means to probe BNV interactions. In this study, for the first time, we employ a robust effective field theory (EFT) approach to estimate the decay widths of two-body decays of hydrogen atom into standard model particles, by utilizing the constraints on the EFT cutoff scale derived from conventional nucleon decay processes. We integrate low energy effective field theory (LEFT), chiral perturbation theory (ChPT), and standard model effective field theory (SMEFT) to formulate the decay widths in terms of the LEFT and SMEFT Wilson coefficients (WCs), respectively. By applying the bounds on the WCs from conventional nucleon decays, we provide a conservative estimate on hydrogen BNV decays. Our findings indicate that the bounds on the inverse partial widths of all dominant two-body decays exceed $10^{44}$ years. Among these modes, the least constrained diphoton decay $\Hy\to \gamma\gamma$ might be astrophysically interesting, although the monochromatic photon signal from our Sun is difficult to detect with current near-Earth telescopes.