Performance of electron reconstruction and selection with the CMS detector in proton-proton collisions at √ s = 8 TeV

A search for pair production of third-generation scalar leptoquarks decaying to top quark and τ lepton pairs is presented using proton-proton collision data at a center-ofmass energy of √ s = 8 TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb −1 . The search is performed using events that contain an electron or a muon, a hadronically decaying τ lepton, and two or more jets. The observations are found to be consistent with the standard model predictions. Assuming that all leptoquarks decay to a top quark and a τ lepton, the existence of pair produced, charge −1/3, third-generation leptoquarks up to a mass of 685 GeV is excluded at 95% confidence level. This result constitutes the first direct limit for leptoquarks decaying into a top quark and a τ lepton, and may also be applied directly to the pair production of bottom squarks decaying predominantly via the R-parity violating coupling λ 333 .

Section: Reconstruction and Identification Of Physics Objectsmentioning

confidence: 99%

Search for third-generation scalar leptoquarks in the tτ channel in proton-proton collisions at s = 8 $$ \sqrt{s}=8 $$ TeV

Khachatryan¹,

Sirunyan²,

Tumasyan³

et al. 2015

“…The cluster is then matched to a reconstructed track. The electron selection is based on the shower shape, track-cluster matching, and consistency between the cluster energy and the track momentum [45]. Muon candidates are reconstructed by performing a global fit that requires consistent hit patterns in the tracker and the muon system [46].…”

Section: Jhep11(2017)029mentioning

confidence: 99%

Search for electroweak production of charginos and neutralinos in WH events in proton-proton collisions at $$ \sqrt{s}=13 $$ TeV

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2017

Results are reported from a search for physics beyond the standard model in proton-proton collision events with a charged lepton (electron or muon), two jets identified as originating from a bottom quark decay, and significant imbalance in the transverse momentum. The search was performed using a data sample corresponding to 35.9 fb −1 , collected by the CMS experiment in 2016 at √ s = 13 TeV. Events with this signature can arise, for example, from the electroweak production of gauginos, which are predicted in models based on supersymmetry. The event yields observed in data are consistent with the estimated standard model backgrounds. Limits are obtained on the cross sections for chargino-neutralino ( χ ± 1 χ 0 2 ) production in a simplified model of supersymmetry with the decays χ The CMS collaboration 22 IntroductionSupersymmetry (SUSY) [1][2][3][4][5][6][7][8] is a theoretically attractive extension of the standard model (SM) that is based on a symmetry between bosons and fermions. SUSY predicts the existence of a superpartner for every SM particle, with the same gauge quantum numbers but differing by one half unit of spin. In R-parity conserving SUSY models, supersymmetric particles are created in pairs, and the lightest supersymmetric particle (LSP) is stable [9][10][11]. As a result, SUSY also provides a potential connection to cosmology as the LSP, if neutral and stable, may be a viable dark matter candidate. Previous searches based on 13 TeV proton-proton collision data at the CERN LHC focused on strong production of colored SUSY particles [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Pair production of these particles would have the largest cross section for SUSY processes and therefore provides the strongest discovery potential with small datasets. However, the absence of signals in these searches suggests that strongly produced SUSY particles may be too massive to be found with the present data. In contrast, neutralinos ( χ 0 ) and charginos ( χ ± ), mixtures of the superpartners of the SM electroweak gauge bosons and the Higgs bosons, can have masses within the accessible range. Because of the absence of color charge, the production cross sections are lower, and these particles may have thus far eluded detection. This provides strong motivation for dedicated searches for electroweak SUSY particle production.Depending on the mass spectrum, the charginos and neutralinos can have significant decay branching fractions to vector bosons V (W or Z) and the Higgs boson (H). Here, "H" refers to the 125 GeV Higgs boson [29], interpreted as the lightest CP-even state of an extended Higgs sector. The H boson is expected to have SM-like properties if all of the other Higgs bosons are much heavier [30]. The observation of a Higgs boson in a SUSY-like process would provide evidence that SUSY particles couple to the Higgs field, a necessary condition for SUSY to stabilize the Higgs boson mass. Pair production of neutralinos and/or charginos can thus lead to the HH, VH, and VV decay...

“…Selected events are required to have exactly one electron [37] or muon [38] with p T > 20 GeV and |η| < 1.4442 or |η| < 2.4, respectively. The lepton needs to be consistent with originating from the primary interaction vertex and isolated from other activity in the event.…”

Section: Event Reconstruction and Preselectionmentioning

confidence: 99%

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

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2017

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...