Search for anomalous production of multilepton events in pp collisions at $ \sqrt {s} = 7\,TeV $

Abstract

A search for anomalous production of events with three or more isolated leptons in pp collisions at √ s = 7 TeV is presented. The data, corresponding to an integrated luminosity of 4.98 fb −1 , were collected by the CMS experiment at the LHC during the 2011 run. The search is applicable to any model of new physics that enhances multiple lepton production. The observed multilepton events are categorized into exclusive search channels based on the identity and kinematics of the objects in the events. An estimate of the standard-model background rates from data is emphasized, but simulation is also used to estimate some of the background rates. The search results are interpreted in the context of supersymmetry, including both R-parity-conserving and R-parity-violating models. We derive exclusion limits as a function of squark, gluino, and chargino masses.

Light stau phenomenology and the Higgs γγ rate

“…On the other hand, final states similar to the ones we are interested in have been already investigated by CMS [93] in the context of searches for charginos and neutralinos. However, comparing the cross sections listed in the third column of table 1 to the CMS results, we note that the CMS multilepton searches are still not sensitive to our scenario.…”

Multi-lepton signals of multiple Higgs bosons

“…However, designing such a dedicated search would require a detailed understanding of backgrounds in many channels that is well beyond the scope of a theory-level study. Instead, as done previously in a study of the multi-lepton signatures of the Standard Model Higgs boson [10], we will adopt the selection cuts and background estimates of an existing CMS multi-lepton analysis [8,9] to demonstrate the efficacy of a 2HDM multi-lepton search. In the conclusions, we will comment briefly on how a focussed search could be further optimized to maximize sensitivity to multi-lepton final states arising from an extended scalar sector.…”

“…The CMS multi-lepton search strategy [8,9] is particularly well-suited in this respect, since its power lies in the combination of numerous exclusive channels. While the sensitivity to new physics in any individual channel alone is not necessarily significant, the exclusive combination across multiple channels can provide considerable sensitivity.…”

“…For each benchmark spectrum we combine the 20 exclusive multi-lepton channels to obtain an overall sensitivity as a function of two-dimensional mixing angle parameter spaces that characterize each of the four discrete types of flavor conserving 2HDMs. With this, we identify regions of 2HDM parameter space that are excluded by the existing CMS multi-lepton search [9], as well as those regions where future multi-lepton searches at the LHC will have sensitivity.…”

“…Section 4 is devoted to summarizing the multi-lepton search strategy and the simulation methods we use. The results of our study are displayed in section 5 where we identify the regions of parameter space that are excluded on the basis of the existing CMS multi-lepton search with 5 fb −1 of 7 TeV proton-proton collisions [9] as well as those regions to which future searches will have sensitivity. In section 6 we suggest some refinements to future multi-lepton searches that could enhance the sensitivity to extended Higgs sectors.…”