Searching for apparent baryon number violation in ${\mathrm{\Lambda }}_c^{+}$ decays at the Super Tau-Charm Facility

Observation of baryon number violation (BNV) in laboratory experiments would constitute unambiguous evidence for physics beyond the Standard Model. We propose dedicated searches for $\mathit{\text{apparent}}$ BNV in charm-baryon decays, ${\mathrm{\Lambda }}_c^{+}\to M^{+}+$ missing energy ($M=\pi ,K$) where the missing energy stems from a resonance. These channels have not been explored experimentally so far, despite the relatively clean environment potentially provided by near ${\mathrm{\Lambda }}_c^{+}{\bar{\mathrm{\Lambda }}}_c^{-}$ threshold production at $e^{+}{e}^{-}$ colliders. Performing state-of-the-art Monte Carlo simulations for the proposed Super Tau-Charm Facility (STCF), we evaluate the signal efficiencies and derive projected model-independent sensitivities under the assumption of negligible background. We further interpret these sensitivities within two theoretical frameworks: a sterile-neutrino-extended low-energy effective field theory ($\nu$LEFT) and R-parity-violating (RPV) supersymmetry. With an integrated luminosity of 1 ab${}^{-1}$, STCF can probe new-physics scales of several TeV in the $\nu$LEFT description and constrain the RPV model parameter ${\lambda }_{212}^{\mathrm{\prime }\mathrm{\prime }}\mathrm{/}{m}_{\tilde{q}}^2$ down to about $0.1{\mathrm{T}\mathrm{e}\mathrm{V}}^{-2}$. Our results demonstrate that STCF provides a highly competitive opportunity for probing BNV interactions in rare charm-baryon decays.