In this paper we briefly discuss the estimation of uncertainties in QCD backgrounds to searches for Supersymmetry under development by the ATLAS collaboration.
Supersymmetry (SUSY) is one of the most relevant scenarios of new physics searched by the ATLAS experiment at the CERN Large Hadron Collider. In this writeup the principal search strategies employed by ATLAS are outlined and the most recent results for analyses targeting SUSY discovery are discussed. A wide range of signatures is covered motivated by various theoretical scenarios and topologies: strong production, third-generation fermions, long-lived particles and R-parity violation, among others. The results are based on up to ~5 fb-1 of data recorded during 2010-2011 at sqrt(s) = 7 TeV centre-of-mass energy by the ATLAS experiment at the LHC.
A novel method is proposed here to precisely model the multi-dimensional features of QCD multi-jet events in hadron collisions. The method relies on the schematization of high-pT QCD processes as 2->2 reactions made complex by sub-leading effects. The construction of libraries of hemispheres from experimental data and the definition of a suitable nearest-neighbor-based association map allow for the generation of artificial events that reproduce with surprising accuracy the kinematics of the QCD component of original data, while remaining insensitive to small signal contaminations. The method is succinctly described and its performance is tested in the case of the search for the hh->bbbb process at the LHC.
The latest results from CMS on searches for supersymmetry are presented. Searches involving all-hadronic final states with jets and missing transverse energy, and in final states including one or more isolated leptons are discussed. The results are based on 19.5/fb of LHC proton-proton collisions at sqrt = 8 TeV taken with the CMS detector.
Searches for pair and single production of supersymmetric particles under the assumption that R-parity is violated via a single dominant coupling are presented. A subset of the most recent results from LEP, Tevatron and HERA is selected. The data are in agreement with the Standard Model expectation. Limits on the production cross sections and the masses of supersymmetric particles are derived.