Baryon-Number Violating ${\Lambda }_c$ Decays from Light-Cone Sum Rules

Abstract

Baryon-number-violating decays with missing energy probe new interactions connecting Standard-Model quarks to light invisible fermions. Such signatures can arise from dimension-six operators coupling three quarks to an SM-singlet fermion $\chi$, which escapes detection. With a suitable baryon-number assignment for $\chi$, total baryon number is conserved while its violation is apparent in the visible sector. We study the exclusive decays ${\Lambda }_c\to \pi \bar{\chi }$ and ${\Lambda }_c\to K\bar{\chi }$, determining the required form factors using light-cone sum rules with pion and kaon distribution amplitudes. The calculation includes leading-order two-particle contributions up to twist four and factorisable four-particle terms. Two ${\Lambda }_c$ interpolating currents are employed to assess the current dependence. Using single-operator benchmarks based on collider bounds, we obtain branching fractions of order $10^{-7}$ over sizeable parts of the physical region, with uncertainty envelopes reaching $10^{-6}$ in some scenarios. These are indicative estimates within the retained light-cone expansion. We compare with existing chiral-perturbation-theory and QCD-factorisation estimates and discuss experimental prospects. Future data from STCF and Belle II could probe part of the predicted range, while FCC-ee could reach smaller branching fractions.

arXiv comment20 pages, 6 figures, 4 tables