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

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.

Comments: 9 pages, 8 figures. V3: title modified, matches with version published in Phys. Rev. D