Abstract
A search is performed for long-lived particles that decay into final states that include a pair of electrons or a pair of muons. The experimental signature is a distinctive topology consisting of a pair of charged leptons originating from a displaced secondary vertex. Events corresponding to an integrated luminosity of 19.6 (20.5) inverse femtobarns in the electron (muon) channel were collected with the CMS detector at the CERN LHC in proton-proton collisions at sqrt(s) = 8 TeV. No significant excess is observed above standard model expectations. Upper limits on the product of the cross section and branching fraction of such a signal are presented as a function of the long-lived particle's mean proper decay length. The limits are presented in an approximately model-independent way, allowing them to be applied to a wide class of models yielding the above topology. Over much of the investigated parameter space, the limits obtained are the most stringent to date. In the specific case of a model in which a Higgs boson in the mass range 125-1000 GeV decays into a pair of long-lived neutral bosons in the mass range 20-350 GeV, each of which can then decay to dileptons, the upper limits obtained are typically in the range 0.2-10 fb for mean proper decay lengths of the long-lived particles in the range 0.01-100 cm. In the case of the lowest Higgs mass considered (125 GeV), the limits are in the range 2-50 fb. These limits are sensitive to Higgs boson branching fractions as low as 1E-4.
Highlights
Long-lived particles, which could manifest themselves through their delayed decays to leptons, are predicted in many extensions of the standard model (SM)
In this paper we present an inclusive search for massive, long-lived exotic particles that decay to final states that include a pair of charged lepptffioffi ns using proton-proton collision data collected at s 1⁄4 8 TeV during 2012 with the compact muon solenoid (CMS) detector at the CERN LHC
To ensure that the trigger efficiencies obtained from the sample of Z bosons, in which the leptons are prompt, are valid for leptons from LL particle decay, we examine the trigger efficiency in simulated signal events as a function of the lifetime of the LL particles
Summary
Long-lived particles, which could manifest themselves through their delayed decays to leptons, are predicted in many extensions of the standard model (SM). We search for events containing a pair of electrons or muons (dileptons) originating from a common secondary vertex within the volume of the CMS tracker, and with a significant transverse displacement from the event primary vertex. This topological signature has the potential to provide clear evidence for physics beyond. The neutralino is produced in events containing a pair of squarks, where a squark can decay via the process q~ → qχ~0; χ~0 → lþl−ν Both models predict up to two displaced dilepton vertices per event in the CMS tracker volume, of which we only require one to be found. The ATLAS Collaboration has performed related searches for long-lived particles using different decay channels [12,13], or lower-mass LL particles [14], compared to those considered in this paper
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
