Search for supersymmetry in events with soft leptons, low jet multiplicity, and missing transverse momentum in proton-proton collisions at sqrt(s) = 8 TeV

TL;DR

This paper reports a search for supersymmetric particles with compressed spectra using CMS data at 8 TeV, setting limits on top squark and chargino masses based on specific decay scenarios.

Contribution

It introduces a search strategy targeting compressed supersymmetry scenarios with soft leptons and low jet multiplicity, and sets new exclusion limits on top squark and chargino masses.

Findings

Excluded top squark masses below 316 GeV for Delta m = 25 GeV.

Excluded chargino masses below 307 GeV for specific decay assumptions.

Data are consistent with standard model background expectations.

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.