Exploring GeV-scale Majorana neutrinos in lepton-number-violating Λb0 baryon decays

Abstract

In this work, the lepton-number-violating processes in | Δ L | = 2 decays of Λ 0 b baryon, Λ 0 b → p π + μ − μ − and Λ 0 b → Λ + c π + μ − μ − , 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 τ 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 BR ( Λ 0 b → p π + μ − μ − ) ≲ O ( 10 − 9 – 10 − 8 ) and BR ( Λ 0 b → Λ + c π + μ − μ − ) ≲ O ( 10 − 8 – 10 − 7 ) . Exclusion regions on the parameter space ( m N , | V μ N | 2 ) associated with the heavy neutrino are presented and compared with those from K − → π + μ − μ − (NA48/2) and B − → π + μ − μ − (LHCb) as well as by different search strategies such as NA3, CHARMII, NuTeV, Belle, and DELPHI.