Baryonecrosis: Displaced Vertices from $R$-Parity Violation

Abstract

The LHC has placed stringent limits on superpartner masses, in conflict with naturalness. R-parity violation is one of the few scenarios that allows reduction of these limits and is thus worth significant exploration at the LHC. We demonstrate that if the R-parity violating operator UDD is used, we generically expect all SUSY events at the LHC to have displaced vertices. If a squark is the LSP, it will have a short displaced vertex. If any other particle is the LSP, the displaced vertex is naturally expected to be quite long, possibly even outside the detectors. These scenarios are already constrained by existing searches for missing energy. This arises because this operator efficiently washes-out the baryon asymmetry in the early universe, unless the squarks are heavy and the coupling is small. Avoiding displaced vertices is possible, but requires baryogenesis below the weak scale. Thus, for example, the use of sphalerons in baryogenesis does not avoid the requirement of displaced vertices. This motivates searching for hadronic displaced vertices at the LHC with decay lengths anywhere from tens of microns to meters.