Rare decays of B mesons via on-shell sterile neutrinos

TL;DR

This paper calculates the decay rates of rare B meson decays involving on-shell sterile neutrinos, highlighting their potential observability at Belle II and LHCb experiments, and discusses how neutrino lifetime affects detection prospects.

Contribution

It provides the first detailed calculation of B meson rare decay rates via on-shell sterile neutrinos, considering neutrino lifetime effects and CKM suppression factors.

Findings

Decay rates depend on neutrino lifetime and decay channels.

Decays involving charmed mesons avoid CKM suppression.

Potential detection at Belle II and LHCb with missing momentum signatures.

Abstract

In view of the projected high number of produced $B$ mesons in Belle II experiment ($\sim 10^{10}$ per year), in addition to the presently ongoing LHC-b, we calculate the rate of decay for the rare decays of $B$ mesons via a sterile on-shell neutrino $N$, which subsequently may decay leptonically or semileptonically within the detector: $B \to (D^{(*)}) \ell_1^{\pm} N$, then $N \to \ell_1^{\pm} \ell_2^{\mp} \nu$ or $N \to \ell^{\pm} \pi^\mp$. Here, $\ell_1 \not= \ell_2$ in order to avoid serious QED background. We account for the possible effects of the strong neutrino lifetime on the observability of the rare decays. If no charmed mesons ($D^{(*)}$) are produced at the first vertex of the sterile neutrino, a strong CKM-suppression becomes effective; this is not true if we consider instead the decays of $B_c$ mesons which can be produced copiously in LHC-b. The production of charmed mesons $D^{(*)}$ at the first vertex offers an attractive possibility because it avoids strong CKM-suppression. Such rare decays of $B$ mesons could be detected at Belle II experiment, with $N$ neutrino either decaying within the detector or manifesting itself as a massive missing momentum.