Search for massive, long-lived particles using multitrack displaced vertices or displaced lepton pairs inppcollisions ats=8  TeV

Abstract

Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. This analysis uses a data sample of proton-proton collisions at ffiffi ffi s p ¼ 8 TeV corresponding to an integrated luminosity of 20.3 fb −1 collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split supersymmetry, and gauge mediation. In some of the search channels, the trigger and search strategy are based only on the decay products of individual long-lived particles, irrespective of the rest of the event. In these cases, the provided limits can easily be reinterpreted in different scenarios.

Simplified phenomenology for colored dark sectors

“…This requirement is however insufficient in sight of the current collider bounds. Long-lived coannihilation partners produced at colliders would form Rhadrons [64][65][66] that are constrained up to a few TeV by the current LHC searches [67][68][69][70][71][72].…”

R-parity violating supersymmetry and neutrino physics: experimental signatures

“…Furthermore the fact that in the low-m 1/2 high-m 0 region theχ 0 1 is slightly long lived, as evident from Fig. 2, opens up the possibility to use searches for displaced vertices [28,29] in order to probe this model at the LHC [30]. Lastly, theχ 0 1 decays to one or two neutrinos give rise to a moderately high E miss T , thus rendering some E miss T -based analyses pertinent to bRPV.…”

“…in 28% of events it would decay within 30 cm and in 44% events within 1 m. Therefore, the µνSSM signal events would be characterised by displaced τ leptons plus neutrinos. This distinctive signature opens up the possibility to exploit current or future variations of analyses carried out by ATLAS and CMS looking for a displaced muon and tracks [28,29] or searching for displaced dileptons [57,29], dijets [58] or muon jets [59] arising in Higgs decays to pairs of long-lived invisible particles. In Fig.…”

Long-lived colored scalars at the LHC

“…The search has a highest mass exclusion of scalar top quark with mass below 790 GeV and a proper lifetime of 2 cm/c. The ATLAS collaboration has performed a very comprehensive study of displaced vertices, targeting long-lived particles decaying into two leptons or five or more charged particles [9]. Limits are set on models of R-parity violation, split SUSY, and gauge mediated SUSY breaking.…”

“…Therefore, to probe long-lived particle decays, especially within the inner detector, analyses must incorporate dedicated triggers and beyond the accustomed particle reconstruction algorithms. The latter should have the potential to pin down the origin of many particles (tracks) to one single displaced vertex [5,6,9].…”