Search for lepton-number-violating signals in the charm sector

TL;DR

This paper investigates lepton-number-violating decays of the $D^0$ meson as potential evidence for Majorana neutrinos, assessing LHCb's sensitivity to these rare processes and their implications for sterile neutrino models.

Contribution

It introduces a novel search for $| riangle L|=2$ $D^0$ decays in charm physics and evaluates LHCb's potential to improve experimental bounds on such processes.

Findings

LHCb could detect branching ratios as low as 10^{-9} with 300 fb^{-1}

Potential to surpass previous experimental bounds from E791

Constraints on sterile neutrino parameter space from these searches

Abstract

We explore signals of lepton-number-violation in the charm physics sector. We study the four-body $|\Delta L|= 2$ decays of the $D^0$ meson, $D^0 \to P^- \pi^-\mu^+ \mu^+$ ($P = \pi, K$) as an alternative evidence of the Majorana nature of neutrinos. We carry out an exploratory study on the potential sensitivity that LHCb experiment could achieve for these $|\Delta L|= 2$ processes. We show that for a long term expected integrated luminosity of 300 fb$^{-1}$, a signal significance of branching ratios of the order $\mathcal{O}(10^{-9})$ might be accessible, allowing to improve the experimental bounds obtained by the E791 experiment. Limits on the parameter space of a heavy sterile neutrino that could be obtained from their experimental search are discussed as well.