Search for baryon and lepton number violating decays $\boldsymbol{D \rightarrow p\ell}$

TL;DR

This study searches for rare baryon and lepton number violating decays of D mesons into a proton and a lepton, using a large dataset, and sets upper limits on their branching fractions due to no observed signals.

Contribution

First search for D meson decays violating baryon and lepton number, establishing upper limits on branching fractions with a large Belle dataset.

Findings

No significant signals observed.

Upper limits on branching fractions are (5-8) x 10^{-7}.

Results constrain new physics models.

Abstract

We search for the baryon and lepton number violating charm decays, $D \rightarrow p\ell$, where $D$ is either a $D^0$ or a $\overline{D}^0$ and $\ell$ is a muon or an electron, using a data sample of $921\,\mathrm{fb}^{-1}$ collected by the Belle detector at the KEKB asymmetric energy $e^{+}e^{-}$ collider. In the absence of significant signals, we set upper limits on the branching fractions in the range $(5 - 8) \times 10^{-7}$ at a 90\% confidence level, depending on the decay mode.