Nucleon decays into three leptons: Noncontact contributions

TL;DR

This paper systematically analyzes nucleon decays into three leptons induced by dimension-6 baryon number violating operators, providing new bounds and more reliable estimates compared to previous phase-space calculations.

Contribution

It classifies noncontact contributions to nucleon decays into three leptons, formulates decay widths in terms of Wilson coefficients, and derives improved bounds from experimental data.

Findings

Stringent bounds on triple-lepton nucleon decay rates from current limits.

Significant variation in bounds depending on the specific operator.

Discrepancies with previous phase-space estimates by several orders of magnitude.

Abstract

We investigate baryon number violating (BNV) nucleon decays into three leptons from noncontact contributions that are induced by dimension-6 (dim-6) BNV operators in low-energy effective field theory (LEFT) with an exchange of a baryon, meson, lepton, or photon field. We systematically classify all these processes that change lepton flavor by one unit and formulate their decay widths in terms of the dim-6 LEFT Wilson coefficients. By applying constraints on these Wilson coefficients derived from current experimental limits on BNV two-body nucleon decays, we obtain stringent bounds on the rates of these triple-lepton modes. These bounds vary significantly from one dim-6 operator to another under consideration. Our results for the $\Delta(B-L)=0$ modes differ by several orders of magnitude from previous phase-space estimates in the literature, thereby providing a more reliable assessment of their potential occurrence. In addition, we provide improved bounds on $\Delta(B+L)=0$ modes compared to the existing experimental limits.