Searching for supersymmetry with same-sign di-leptons using the CMS experiment at the Large Hadron Collider.

摘要

The year 2010 marked the beginning of a new era in collider physics as the Large Hadron Collider (LHC) began colliding proton beams at a record-setting, center-of-mass energy of 7 TeV. The work described herein represents one of the first efforts to search for evidence of R-parity conserving supersymmetry (SUSY) using the Compact Muon Solenoid (CMS) experiment at the LHC. The analysis exploits an event topology based on same-sign di-leptons, hadronic jets, and missing transverse energy. This signature is expected to be featured in a variety of new physics scenarios and is known to be heavily suppressed by the Standard Model. The search uses data produced during the 2010 LHC run, corresponding to fL d t = 35 pb-1. An extensive overview of the data-driven methods used to model the behavior of background processes is given. After imposing the event selection requirements that define the signal region, 1 event is observed, which is statistically consistent with the total expected Standard Model background rate of 0.80 +/- 0.33. Given this lack of an excess, exclusion limits are calculated on the parameter space of SUSY models with universal gaugino and scalar mass scales. The general limit on cross-section ! multiplied by branching ratio BR and the event selection acceptance Aexperiment is sigma x BR x Aexperiment < 13 pb at 95% C.L. In order to make the results of this search accessible to the wider theoretical community, a parameterization of the experimental acceptance is presented. Using this parameterization, the viability of a large class of new physics models, not restricted to supersymmetry, can be tested against the limits set by this search.