Abstract
Results are presented from a search for supersymmetric particles in scenarios with a compressed mass spectrum. The data sample corresponds to 19.7 inverse femtobarns of proton-proton collisions recorded by the CMS experiment at sqrt(s) = 8 TeV. The search targets top squark pair production in scenarios with mass differences Delta m = m(top squark) - m(neutralino) below the W-boson mass and with top-squark decays in the four-body mode (top squark to b l nu neutralino), where the neutralino is assumed to be the lightest supersymmetric particle (LSP). The signature includes a high transverse momentum (pt) jet associated with initial-state radiation, one or two low-pt leptons, and significant missing transverse energy. The event yields observed in data are consistent with the expected background contributions from standard model processes. Limits are set on the cross section for top squark pair production as a function of the top squark and LSP masses. Assuming a 100% branching fraction for the four-body decay mode, top-squark masses below 316 GeV are excluded for Delta m = 25 GeV at 95% CL. The dilepton data are also interpreted under the assumption of chargino-neutralino production, with subsequent decays to sleptons or sneutrinos. Assuming a difference between the common lightest chargino/next lightest neutralino mass and the LSP mass of 20 GeV and a tau-enriched decay scenario, masses in the range m(chargino) < 307 GeV are excluded at 95% CL.
Highlights
The main objectives of the CERN LHC programme include searches for new physics, in particular supersymmetry (SUSY) [1,2,3,4,5], one of the most promising extensions of the standard model (SM) of particle physics
The√data sample corresponds to 19.7 fb−1 of proton–proton collisions recorded by the CMS experiment at s = 8 TeV
In this paper we investigate the production of supersymmetric particles in a scenario in which the mass splitting between the next-to-lightest SUSY particle (NLSP) and the lightest supersymmetric particle (LSP) is small, which is referred to as compressed SUSY
Summary
The main objectives of the CERN LHC programme include searches for new physics, in particular supersymmetry (SUSY) [1,2,3,4,5], one of the most promising extensions of the standard model (SM) of particle physics. In SUSY models with R-parity [8] conservation, sparticles are pair-produced and their decay chains end with the lightest supersymmetric particle (LSP). In this paper we investigate the production of supersymmetric particles in a scenario in which the mass splitting between the next-to-lightest SUSY particle (NLSP) and the LSP is small, which is referred to as compressed SUSY. In this case, the events would escape classical search strategies because of the low transverse momenta (pT) of the decay products of the NLSP. For small χ1+ − χ10 mass splittings, the leptons in the final state would be soft and within the signal region of the dilepton search
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