${\Lambda }_b\to {\Lambda }^{(\ast )}\nu \bar{\nu }$ decays and the recent Belle-II $B^{+}\to K^{+}\nu \bar{\nu }$ data

Abstract

The Belle-II experiment has recently reported the first measurement of $B^{+}\to K^{+}\nu \bar{\nu }$ decay which exceeds the Standard Model prediction by approximately 2.7$\sigma$. The deviation may indicate the presence of new physics beyond the Standard Model in the $b\to s\nu \bar{\nu }$ sector. Under this assumption, we study the hadronic ${\Lambda }_b\to \Lambda (\to p\pi )\nu \bar{\nu }$ and ${\Lambda }_b\to {\Lambda }^{\ast }(\to N\bar{K})\nu \bar{\nu }$ decays within both the Standard Model and beyond. We work in a low energy effective field theory framework with additional light right-handed neutrinos. We calculate the differential branching ratios of these decay modes and explore the implications of the Belle-II results through various observables.

Comments: 11 pages, 4 figures, 6 tables