CP Violation in Pseudo-Dirac Fermion Oscillations

TL;DR

This paper investigates CP violation in pseudo-Dirac fermion oscillations within supersymmetric models with broken $U(1)_R$ symmetry, highlighting potential observable effects like same sign dilepton asymmetries.

Contribution

It provides a comprehensive analysis of fermion-antifermion oscillations, including decay and CP violation effects, in models with small Majorana mass terms.

Findings

Large CP violation (order 1) is possible in these oscillations.

Decays into leptonic final states can produce observable same sign dilepton asymmetries.

Oscillation effects could serve as signatures of $U(1)_R$ breaking in collider experiments.

Abstract

Supersymmetric theories with a $U(1)_R$ symmetry have Dirac gauginos, solve the supersymmetric flavor and CP problems, and have distinctive collider signatures. However when supergravity is included, the $U(1)_R$ must be broken, adding small Majorana mass terms which split the mass of the two components of the Dirac gaugino and lead to oscillations between $U(1)_R$ charge eigenstates. We present a general study of fermion-antifermion oscillations in this system, including the effects of decays and CP violation. We consider the effects of such oscillations in the case where the two $U(1)_R$ charge eigenstates can decay into the same final state, and show that $O(1)$ CP violation is allowed. In the case of decays into final states containing leptons such CP violation can be observed as a same sign dilepton asymmetry.