Sterile neutrinos in $Λ_b^0\to (Λ_c^+,p^+)\ell^-_1\ell^-_2\ell^+_3ν$ decays

Abstract

We study lepton number violating and lepton number conserving semi-leptonic decays of heavy baryons Λ 0 b to three charged leptons and a neutrino. The decays occur through two intermediate quasi-degenerate GeV-scale sterile neutrinos of either Majorana or Dirac type that can be on-shell. Interference between the intermediate heavy neutrinos leads to CP violation in the final states. Effect of neutrino oscillations between the heavy states are also considered in observables of interests, i.e., branching ratio, and the CP-asymmetry. Given the present constraints on the heavy-to-light mixing elements |V eN | and |V µN |, CP-averaged branching ratio of Λ 0 b → (Λ c , p)µµeν with intermediate Majorana neutrinos is almost two orders of magnitude larger than for the same with Dirac neutrinos, whereas, CP-averaged branching ratio of Λ 0 b → (Λ c , p)eeµν is of the same order of magnitude for both Majorana and Dirac neutrino induced decays. CP-violation is found to be appreciable when the neutrino mass difference is comparable with the average decay widths.

$Δ$L=2 hyperon decays induced by Majorana neutrinos and doubly-charged scalars

“…On the other hand, ∆L = 2 hyperon decays allow the possibility to study channels involving equal-sign muon and electrons in the final state that are not available in nuclear decays due to limited phase space. There is a large amount of studies related to ∆L = 2 processes in decays of tau leptons [9][10][11][12][13][14][15][16], pseudoscalar mesons [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33], and Λ b baryons [34][35][36][37], mainly motivated by the resonant effect produced by an intermediate Majorana neutrino and their study in flavor-factories experiments; this new study is motivated by the large dataset of hyperons pairs produced in charmonium decays that has been and are expected to be accumulated in the BESIII experiment [38,39].…”