Mathematics / Matematik
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Article Citation - WoS: 13Citation - Scopus: 14Search for R-Parity Violating Decays of a Top Squark in Proton–proton Collisions at √s=8 Tev(Elsevier B.V., 2016) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Gomez, G.The results of a search for a supersymmetric partner of the top quark (top squark), pair-produced in proton–proton collisions at s=8 TeV, are presented. The search, which focuses on R-parity violating, chargino-mediated decays of the top squark, is performed in final states with low missing transverse momentum, two oppositely charged electrons or muons, and at least five jets. The analysis uses a data sample corresponding to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in 2012. The data are found to be in agreement with the standard model expectation, and upper limits are placed on the top squark pair production cross section at 95% confidence level. Assuming a 100% branching fraction for the top squark decay chain, t˜→tχ˜1 ±,χ˜1 ±→ℓ±+jj, top squark masses less than 890 (1000) GeV for the electron (muon) channel are excluded for the first time in models with a single nonzero R-parity violating coupling λijk ′ (i,j,k≤2), where i,j,k correspond to the three generations. © 2016 The Author(s)Article Citation - WoS: 8Citation - Scopus: 9Search for Supersymmetry in Electroweak Production With Photons and Large Missing Transverse Energy in Pp Collisions at √s=8tev(Elsevier B.V., 2016) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Fernandez, M.Results are reported from a search for supersymmetry with gauge-mediated supersymmetry breaking in electroweak production. Final states with photons and large missing transverse energy (ET miss) were examined. The data sample was collected in pp collisions at s=8TeV with the CMS detector at the LHC and corresponds to 7.4fb−1. The analysis focuses on scenarios in which the lightest neutralino has bino- or wino-like components, resulting in decays to photons and gravitinos, where the gravitinos escape undetected. The data were obtained using a specially designed trigger with dedicated low thresholds, providing good sensitivity to signatures with photons, ET miss, and low hadronic energy. No excess of events over the standard model expectation is observed. The results are interpreted using the model of general gauge mediation. With the wino mass fixed at 10GeV above that of the bino, wino masses below 710GeV are excluded at 95% confidence level. Constraints are also set in the context of two simplified models, for which the analysis sets the lowest cross section limits on the electroweak production of supersymmetric particles. © 2016 The AuthorArticle Citation - WoS: 23Citation - Scopus: 26Search for Supersymmetry in Events With Soft Leptons, Low Jet Multiplicity, and Missing Transverse Energy in Proton–proton Collisions at √s=8 Tev(Elsevier B.V., 2016) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Palencia Cortezon, E.Results are presented from a search for supersymmetric particles in scenarios with small mass splittings. The data sample corresponds to 19.7 fb−1 of proton–proton collisions recorded by the CMS experiment at s=8 TeV. The search targets top squark (t˜) pair production in scenarios with mass differences Δm=m(t˜)−m(χ˜1 0) below the W-boson mass and with top-squark decays in the four-body mode (t˜→bℓνχ˜1 0), where the neutralino (χ˜1 0) is assumed to be the lightest supersymmetric particle (LSP). The signature includes a high transverse momentum (pT) jet associated with initial-state radiation, one or two low-pT leptons, and significant missing transverse energy. The event yields observed in data are consistent with the expected background contributions from standard model processes. Limits are set on the cross section for top squark pair production as a function of the t˜ and LSP masses. Assuming a 100% branching fraction for the four-body decay mode, top-squark masses below 316 GeV are excluded for Δm=25 GeV at 95% CL. The dilepton data are also interpreted under the assumption of chargino–neutralino production, with subsequent decays to sleptons or sneutrinos. Assuming a difference between the common χ˜1 +/χ˜2 0 mass and the LSP mass of 20 GeV and a τ-enriched decay scenario, masses in the range m(χ˜1 +)<307 GeV are excluded at 95% CL. © 2016 The AuthorArticle Citation - WoS: 40Citation - Scopus: 41Search for Supersymmetry in the Multijet and Missing Transverse Momentum Final State in Pp Collisions at 13 Tev(Elsevier B.V., 2016) Khachatryan, V.; Karapınar, Güler; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Castineiras De Saa, J.R.A search for new physics is performed based on all-hadronic events with large missing transverse momentum produced in proton–proton collisions at s=13 TeV. The data sample, corresponding to an integrated luminosity of 2.3 fb−1, was collected with the CMS detector at the CERN LHC in 2015. The data are examined in search regions of jet multiplicity, tagged bottom quark jet multiplicity, missing transverse momentum, and the scalar sum of jet transverse momenta. The observed numbers of events in all search regions are found to be consistent with the expectations from standard model processes. Exclusion limits are presented for simplified supersymmetric models of gluino pair production. Depending on the assumed gluino decay mechanism, and for a massless, weakly interacting, lightest neutralino, lower limits on the gluino mass from 1440 to 1600 GeV are obtained, significantly extending previous limits. © 2016 The Author