Same-sign trileptons at the LHC: a window to lepton-number violating supersymmetry

Abstract

We present a detailed investigation to establish that lepton-number (L) violating supersymmetry (SUSY) can be effectively probed at the LHC in the practically background-free same-sign trilepton (SS3ℓ) and same-sign four-lepton (SS4ℓ) channels. With this in view, we extend our earlier analysis of SS3ℓ and SS4ℓ signals by considering situations based on minimal supergravity as well as a phenomenological SUSY model. We find that the R-parity violating scenario predicts large event rates, for both the 7 and 14 TeV runs. Furthermore, we show that it is extremely unlikely to ever achieve similar rates in R-parity conserving SUSY. In addition, we show how SS3ℓ and SS4ℓ, in conjunction with the mixed-sign trilepton and four-lepton channels, can be used to extract dynamical information about the underlying SUSY theory, namely, the Majorana character of the decaying lightest neutralino and the nature of L-violating couplings. We define suitable variables and relationships between them which can be verified experimentally and which are largely independent of the SUSY production cross sections and the cascade decay branching fractions. These theoretical predictions are validated by Monte Carlo simulations including detector and background effects.