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Search for stealth supersymmetry in events with jets, either photons or leptons, and low missing transverse momentum in pp collisions at 8 TeV  [PDF]
CMS Collaboration
Physics , 2014, DOI: 10.1016/j.physletb.2015.03.017
Abstract: The results of a search for new physics in final states with jets, either photons or leptons, and low missing transverse momentum are reported. The study is based on a sample of proton-proton collisions collected at center-of-mass energy sqrt(s) = 8 TeV with the CMS detector in 2012. The integrated luminosity of the sample is 19.7 inverse femtobarns. Many models of new physics predict the production of events with jets, electroweak gauge bosons, and little or no missing transverse momentum. Examples include stealth models of supersymmetry (SUSY), which predict a hidden sector at the electroweak energy scale in which SUSY is approximately conserved. The data are used to search for stealth SUSY signatures in final states with either two photons or an oppositely charged electron and muon. No excess is observed with respect to the standard model expectation, and the results are used to set limits on squark pair production in the stealth SUSY framework.
Search for supersymmetry at the CMS in all-hadronic final state  [PDF]
Gheorghe Lungu,for the CMS collaboration
Physics , 2009,
Abstract: We present a search for supersymmetry (SUSY) in the fully hadronic final state with the CMS detector at the LHC. This final state contains at least two jets and a significant transverse energy imbalance due to neutralinos escaping detection. The background to all-hadronic signature arise from QCD multijet production, ttbar and electroweak boson+jet production. These background can be estimated by utilizing a data-driven approach using events thus enabling a possible discovery of SUSY in the early physics data. In addition to the generic search, we also present an analysis which utilizes a new quantity, alpha_T, constructed exclusively from the transverse energies of the jets to effectively eliminate the QCD background.
Search for supersymmetry in events with photons and low missing transverse energy in pp collisions at sqrt(s) = 7 TeV  [PDF]
CMS Collaboration
Physics , 2012, DOI: 10.1016/j.physletb.2012.12.055
Abstract: Many models of new physics, including versions of supersymmetry (SUSY), predict production of events with low missing transverse energy, electroweak gauge bosons, and many energetic final-state particles. The stealth SUSY model yields this signature while conserving R-parity by means of a new hidden sector in which SUSY is approximately conserved. The results of a general search for new physics, with no requirement on missing transverse energy, in events with two photons and four or more hadronic jets are reported. The study is based on a sample of proton-proton collisions at sqrt(s) = 7 TeV corresponding to 4.96 inverse femtobarns of integrated luminosity collected with the CMS detector in 2011. Based on good agreement between the data and the standard model expectation, the data are used to determine model-independent cross-section limits and a limit on the squark mass in the framework of stealth SUSY. With this first study of its kind, squark masses less than 1430 GeV are excluded at the 95% confidence level.
Search for Natural SUSY with inclusive search strategies at the LHC using the CMS detector  [PDF]
Sezen Sekmen for the CMS Collaboration
Physics , 2013,
Abstract: Natural SUSY suggests the existence of light stop quarks, accessible at the LHC, which are the focus of a dedicated CMS search program. I present two inclusive CMS searches that look for TeV scale colored sparticles in final states with jets, b-tagged jets and missing transverse energy performed using up to 19.4fb-1 of 8TeV LHC proton-proton data. No deviation from the Standard Model was observed in these searches, and the implications for this was shown for several simplified model scenarios and phenomenological MSSM.
Electroweak boson production in heavy-ion collisions with CMS  [PDF]
Michael Gardner
Physics , 2013, DOI: 10.1088/1742-6596/509/1/012071
Abstract: The Compact Muon Solenoid (CMS) is fully equipped to measure leptonic decays of electroweak probes in the high multiplicity environment of nucleus-nucleus collisions. Electroweak boson production is an important benchmark process at hadron colliders. Precise measurements of W and Z production in heavy-ion collisions can help to constrain nuclear PDFs as well as serve as a standard candle of the initial state in PbPb collisions at the LHC energies. The inclusive and differential measurements of the Z boson yield in the muon and electron decay channel will be presented, establishing that no modification is observed with respect to pp collisions, scaled by the number of incoherent nucleon-nucleon collisions.
SUSY Scalar Production in the Electroweak Sudakov Regime of Lepton Colliders  [PDF]
M. Beccaria,M. Melles,F. M. Renard,C. Verzegnassi
Physics , 2001, DOI: 10.1103/PhysRevD.65.093007
Abstract: We consider the production of SUSY scalar pairs at lepton colliders, for c.m. energies much larger than the mass of the heaviest SUSY (real or virtual) particle involved in the process. In that energy regime, we derive the leading and subleading terms of the electroweak Sudakov logarithms in the MSSM, first working at one loop with physical states and then resumming to all orders with asymptotic expansions. We show that the first order of the resummed expression reproduces the physical one loop approximation, and compute systematically the possible effects on various observables both at one loop and to all orders. We discuss the regimes and the processes where the one loop approximation can or cannot be trusted, working in an energy range between 1 TeV and 4 TeV under a "light" SUSY mass assumption. As a byproduct of our analysis, we propose a determination of the MSSM parameter tan(beta) showing how a relative accuracy of about 25 percent can be easily achieved in the region tan(beta)>14, under reasonable experimental assumptions.
Search for Electroweak Production of Single Top Quarks at DZero  [PDF]
A. P. Heinson,for the DZero Collaboration
Physics , 2001, DOI: 10.1142/S0217751X01007005
Abstract: This paper discusses a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb.
Search for new physics using events with two same-sign isolated leptons in the final state at CMS  [PDF]
Santiago Folgueras
Physics , 2013, DOI: 10.1051/epjconf/20136020036
Abstract: We present a search for new physics using events with two same-sign isolated leptons with/out the presence of b-jets in the final state, targetting two very different SUSY scenarios, one dominated by strong production of squarks and gluinos where the 3rd generation squarks are lighter than other squarks and the other dominated by electroweak production neglecting completely any strongly interacting particles. No excees above the standard model background is observed. The results are interpreted in various SUSY models.
Measurement of Electroweak Vector Boson Pair Production in pp Collision with the CMS Detector at LHC  [PDF]
Ajay Kumar
Physics , 2014,
Abstract: We present an overview of measurements of electroweak vector boson pair production and anomalous Triple Gauge Couplings (aTGC), with semileptonic and fully leptonic final states. The data analyzed were taken at center of mass energy of 7 & 8 TeV by the CMS detector at the Large Hadron Collider. The cross-section measurements are important because they are test of the Standard Model predictions, while these processes serve as background for Higgs searches and various other processes.
Search for invisible Higgs boson production with the CMS detector at the LHC  [PDF]
Matthew E. Chasco for the CMS Collaboration
Physics , 2013,
Abstract: Results are presented for the search for invisible Higgs boson production using the full LHC dataset corresponding to integrated luminosity of 5.1 fb^-1 and 19.6 fb^-1 of proton-proton collision data at sqrt(s)= 7 TeV and 8 TeV (respectively) collected by the CMS detector. The invisible Higgs is searched for in final states of missing transverse energy, with two leptons from a recoiling Z boson. No significant excess is found beyond standard model predictions, and limits are obtained on the branching fraction of the Higgs boson to invisible particles.
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