Search for anomalous production of prompt like-sign lepton pairs at $ \sqrt{s}=7\;\mathrm{TeV} $ with the ATLAS detector

Abstract

An inclusive search for anomalous production of two prompt, isolated leptons with the same electric charge is presented. The search is performed in a data sample corresponding to 4.7 fb −1 of integrated luminosity collected in 2011 at √ s = 7 TeV with the ATLAS detector at the LHC. Pairs of leptons (e ± e ± , e ± µ ± , and µ ± µ ± ) with large transverse momentum are selected, and the dilepton invariant mass distribution is examined for any deviation from the Standard Model expectation. No excess is found, and upper limits on the production cross section of like-sign lepton pairs from physics processes beyond the Standard Model are placed as a function of the dilepton invariant mass within a fiducial region close to the experimental selection criteria. The 95% confidence level upper limits on the cross section of anomalous e ± e ± , e ± µ ± , or µ ± µ ± production range between 1.7 fb and 64 fb depending on the dilepton mass and flavour combination. Keywords: Hadron-Hadron ScatteringArXiv ePrint: 1210.4538Open Access, Copyright CERN, for the benefit of the ATLAS collaboration [12][13][14] may produce final states with two like-sign leptons. In the analysis described here, pairs of isolated, high-p T leptons are selected, and the invariant mass of the dilepton system (e ± e ± , e ± µ ± , µ ± µ ± ) is examined for the inclusive final state and separately for positively-and negativelycharged pairs. The ATLAS Collaboration has previously reported inclusive searches for new physics in the like-sign dilepton final state in a data sample corresponding to an integrated luminosity of 34 pb −1 [15] and in like-sign muon pairs with 1.6 fb −1 [16]. No significant deviation from SM expectations was observed, and fiducial production cross-section limits as well as limits on several specific models of physics beyond SM were derived. The CDF Collaboration has -1 - JHEP12(2012)007performed similar inclusive searches [17, 18] without observing any evidence for new physics. Furthermore, the ATLAS and CMS Collaborations have performed several searches for likesign leptons produced in association with jets or missing transverse momentum where no evidence of non-SM physics was observed [19][20][21][22][23][24][25][26].This article is organised as follows. A brief description of the ATLAS detector is given in section 2. The data and simulation samples, the event selection, and the background determination are explained in sections 3, 4, and 5, respectively. The systematic uncertainties on the background estimate (including theoretical uncertainties on the production cross sections) and signal acceptances are summarised in section 6. In section 7 the number of observed lepton pairs in data is compared to the background estimate, and in section 8 these results are used to derive upper limits on the fiducial cross section for like-sign dilepton production in a kinematic region closely related to the experimental event selection. The ATLAS detectorThe ATLAS detector [27] consists of an inner tracking system, calorimeters, and...

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