Exploring GeV-scale Majorana neutrinos in lepton-number-violating ${\Lambda }_b^0$ baryon decays

Abstract

In this work, the lepton-number-violating processes in $|\Delta L|=2$ decays of ${\Lambda }_b^0$ baryon, ${\Lambda }_b^0\to p{\pi }^{+}{\mu }^{-}{\mu }^{-}$ and ${\Lambda }_b^0\to {\Lambda }_c^{+}{\pi }^{+}{\mu }^{-}{\mu }^{-}$, are investigated for the first time, via an intermediate on-shell Majorana neutrino $N$ with a mass in the GeV scale. We explore the experimental sensitivity of these dimuon channels at the LHCb and CMS experiments, in which heavy neutrino lifetimes in the accessible ranges of ${\tau }_N=[1,100,1000]$ ps are considered. For a integrated luminosity collected of 10 and 50 fb${}^{-1}$ at the LHCb and 30, 300 and 3000 fb${}^{-1}$ at the CMS, we found significant sensitivity on branching fractions of the order $\mathrm{BR}({\Lambda }_b^0\to p{\pi }^{+}{\mu }^{-}{\mu }^{-})\lesssim \mathcal{O}(10^{-9}-10^{-8})$ and $\mathrm{BR}({\Lambda }_b^0\to {\Lambda }_c^{+}{\pi }^{+}{\mu }^{-}{\mu }^{-})\lesssim \mathcal{O}(10^{-8}-10^{-7})$. Exclusion regions on the parameter space ($m_N,|V_{\mu N}{|}^2$) associated with the heavy neutrino are presented and compared with those from $K^{-}\to {\pi }^{+}{\mu }^{-}{\mu }^{-}$ (NA48/2) and $B^{-}\to {\pi }^{+}{\mu }^{-}{\mu }^{-}$ (LHCb) as well as by different search strategies such as NA3, CHARMII, NuTeV, Belle, and DELPHI.

Comments: 13 pages, 10 figures. v3: matches with version published in Phys. Rev. D