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

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.