CP violation with GeV-scale Majorana neutrino in $\Lambda_b\to(\Lambda_c^+, p^+)\pi^+\mu^-\mu^-$ decays

TL;DR

This paper investigates CP violation in specific baryonic decays mediated by quasi-degenerate Majorana neutrinos, showing potential for experimental detection and new constraints on neutrino properties.

Contribution

It introduces the possibility of observing CP violation in baryonic decays via on-shell Majorana neutrinos and discusses how experimental searches can constrain neutrino parameters.

Findings

CP asymmetry can be significant with quasi-degenerate Majorana neutrinos.

Decay rates are suppressed but potentially observable at the LHC.

Constraints from these decays complement existing bounds on neutrino properties.

Abstract

We explore the possibility of CP violation in baryonic $\Lambda_b\to(\Lambda_c^+, p^+)\pi^+\mu^-\mu^-$ decays which are mediated by two Majorana sterile neutrino and are $|\Delta L|=2$ lepton number violating processes. Appreciable CP asymmetry can be obtained if there are two on-shell Majorana neutrinos that are quasi-degenerate in mass with the mass difference of the order of average decay widths. We find that given the present constraints on the heavy to light mixing element $|V_{\mu N}|$, the $\Lambda_b\to p^+\pi^+\mu^-\mu^-$ and $\Lambda_b\to \Lambda_c^+\pi^+\mu^-\mu^-$ decay rates are suppressed but could be within the experimental reach at the LHC. If searches of the modes are performed, then experimental limits on the rates can be translated to constraints on the Majorana neutrino mass $m_N$ and heavy to light mixing element squared $|V_{\mu N}|^2$. We show that the constraints on the $(m_N, |V_{\mu N}|^2)$ parameter space coming from the $|\Delta L| = 2$ baryonic decays are complementary to the bounds coming from other processes.