Search for top squark pair production in pp collisions at s = 13 $$ \sqrt{s}=13 $$ TeV using single lepton events

Abstract

A search for top squark pair production in pp collisions at √ s = 13 TeV is performed using events with a single isolated electron or muon, jets, and a large transverse momentum imbalance. The results are based on data collected in 2016 with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb −1 . No significant excess of events is observed above the expectation from standard model processes. Exclusion limits are set in the context of supersymmetric models of pair production of top squarks that decay either to a top quark and a neutralino or to a bottom quark and a chargino. Depending on the details of the model, we exclude top squarks with masses as high as 1120 GeV. Detailed information is also provided to facilitate theoretical interpretations in other scenarios of physics beyond the standard model. A Additional information 17The CMS collaboration 22 IntroductionSupersymmetry (SUSY) [1][2][3][4][5][6][7][8] is an extension of the standard model (SM) that postulates the existence of a superpartner for every SM particle with the same gauge quantum numbers but differing by one half-unit of spin. The search for a low mass top squark, the scalar partner of the top quark, is of particular interest following the discovery of a Higgs boson [9][10][11], as it would substantially contribute to the cancellation of the divergent loop corrections to the Higgs boson mass, providing a possible solution to the hierarchy problem [12][13][14].We present results of a search for top squark pair production in the final state with a single lepton ( = e or µ) with high transverse momentum (p T ), jets, and significant p T imbalance. Dedicated top squark searches have been carried out by the ATLAS [15] and CMS [16,17] collaborations based on 13 TeV proton-proton (pp) collisions at the CERN LHC, with data sets corresponding to integrated luminosities of 3.2 and 2.3 fb −1 , respectively. In this paper we report on an extension of the search of ref.[16] in the single-lepton final state that exploits the data sample collected with the CMS detector [18] in 2016, corresponding to the much larger integrated luminosity of 35.9 fb −1 . We find no evidence for an excess of events above the expected background from standard model processes, and interpret the results as limits on simplified models [19][20][21][22] of the pair production of top squarks ( t) Figure 1. Simplified-models diagrams corresponding to top squark pair production, followed by the specific decay modes targeted in this paper. (a) pp → t t → t χdecaying into top quarks and neutralinos ( χ 0 1 ) and/or bottom quarks and charginos ( χ ± 1 ), as shown in figure 1. We take the χ 0 1 to be the lightest supersymmetric particle (LSP) and to be stable. The CMS detectorThe central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter, and a brass and scintillat...

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