Exploring charm decays with missing energy in leptoquark models

Abstract

We investigate the possibility that scalar leptoquarks generate consequential effects on the flavor-changing neutral-current decays of charmed hadrons into final states with missing energy ($/E$) carried away by either standard model or sterile neutrinos. We focus on scenarios involving the $R_2$, ${\tilde{R}}_2$, and ${\bar{S}}_1$ leptoquarks and take into account various pertinent constraints, learning that meson-mixing ones and those inferred from collider searches can be of significance. We find in particular that the branching fractions of charmed meson decays $D\to M/E$, $M=\pi ,\rho$, and $D_s\to K^{(\ast )}/E$ and singly charmed baryon decays ${\Lambda }_c^{+}\to p/E$ and ${\Xi }_c\to \Sigma /E$ are presently allowed to attain the $10^{-7}$-$10^{-6}$ levels if induced by $R_2$ and that the impact of ${\tilde{R}}_2$ is comparatively much less. In contrast, the contributions of ${\bar{S}}_1$, which couples to right-handed up-type quarks and the sterile neutrinos, could lead to branching fractions as high as order $10^{-3}$. This suggests that these charmed hadron decays might be within reach of the BESIII and Belle II experiments or future super charm-tau factories and could serve as potentially promising probes of leptoquark interactions with sterile neutrinos.

16 pages, no figure, comments & references added, matches journal version