Signals for minimal supergravity at the CERN Large Hadron Collider. II. Multilepton channels

We use isajet to perform a detailed study of the multilepton signals expected from cascade decays of supersymmetric particle produced at the CERN LHC. Our analysis is performed within the framework of the minimal supergravity model with gauge coupling unification and radiative electroweak symmetry breaking. We delineate the regions of parameter space where jets plus missing energy plus 1, 2 (opposite-sign and same-sign dileptons), and 3 isolated lepton events should be visible above standard model backgrounds. We find that if any ${E}_{T}$ signal at the LHC is to be attributed to gluino and/or squark production, and if ${m}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}}\ensuremath{\lesssim}1$ TeV, then several of these signals must be simultaneously observable. Furthermore, assuming 10 ${\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity, we find that the reach for supersymmetry in the $1\ensuremath{\ell}+\mathrm{jets}+{E}_{T}$ channel extends to ${m}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}}\ensuremath{\sim}2300(1600)$ GeV for ${m}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{q}}\ensuremath{\sim}{m}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}}({m}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{q}}\ensuremath{\sim}1.5{m}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}})$, and exceeds the corresponding reach in the $0\ensuremath{\ell}+{E}_{T}$ channel. We show that measurements of the various topological cross sections, jet, and $B$-hadron multiplicities in these events, together with the charge asymmetry for single lepton and same-sign dilepton events, and flavor asymmetry for opposite-sign dilepton events, serve to narrow the allowed range of underlying SUGRA parameter values. We also delineate parameter regions where signals with clean isolated dilepton (from slepton production) and trilepton events (from chargino or neutralino production) are visible at the LHC, and examine the extent to which these signals can be separated from other SUSY sources.