The performance of the CMS Level-1 Trigger for supersymmetric events at an LHC luminosity of 2 x 1033 cm-2s-1 is reviewed. Energy and momentum trigger thresholds have been chosen to yield a maximum ...Level-1 output rate of 50 kHz, within a safety factor of three. The Level-1 trigger efficiencies for the majority of the channels studied are found to be greater than 90%, which provides a good basis for the High-Level Trigger, where more stringent conditions are applied. Reasons for occasional lower efficiencies are given.
A peaking structure in the J/ psi phi J/ psi phi mass spectrum near threshold is observed in B super( plus or minus ) arrow right J/ psi phi K super( plus or minus )B plus or minus arrow right J/ psi ...phi K plus or minus decays, produced in pp collisions at s=7 TeV collected with the CMS detector at the LHC. The data sample, selected on the basis of the dimuon decay mode of the J/ psi J/ psi , corresponds to an integrated luminosity of 5.2 fb super(-1). Fitting the structure to an S -wave relativistic Breit-Wigner lineshape above a three-body phase-space nonresonant component gives a signal statistical significance exceeding five standard deviations. The fitted mass and width values are m=4148.0 plus or minus 2.4(stat.) plus or minus 6.3(syst.)MeV and Gamma =28-11+15(stat.) plus or minus 19(syst.)MeV, respectively. Evidence for an additional peaking structure at higher J/ psi phi J/ psi phi mass is also reported.
Results are presented of a search for compositeness in electrons and muons using a data sample of pp collisions at a center-of-mass energy s = 7 TeV collected with the CMS detector at the LHC and ...corresponding to an integrated luminosity of 5.0 fb - 1 . Excited leptons (a a) are assumed to be produced via contact interactions in conjunction with a standard model lepton and to decay via a a a a gamma , yielding a final state with two energetic leptons and a photon. The number of events observed in data is consistent with that expected from the standard model. The 95% confidence upper limits for the cross section for the production and decay of excited electrons (muons), with masses ranging from 0.6 to 2 TeV, are 1.48 to 1.24 fb (1.31 to 1.11 fb). Excited leptons with masses below 1.9 TeV are excluded for the case where the contact interaction scale equals the excited lepton mass. The limits on the cross sections are the most stringent ones published to date.
A measurement of the t t A= production cross section in pp collisions at s = 7 TeV is presented. The results are based on data corresponding to an integrated luminosity of 2.3 fb-1 collected by the ...CMS detector at the LHC. Selected events are required to have one isolated, high transverse momentum electron or muon, large missing transverse energy, and hadronic jets, at least one of which must be consistent with having originated from a b quark. The measured cross section is 158.1 +/- 2.1 (stat .) +/- 10.2 (syst .) +/- 3.5 (lum .) pb , in agreement with standard model predictions.
An updated search for heavy narrow resonances decaying to muon or electron pairs using the CMS detector is presented. Data samples from pp collisions at s = 7 TeV and 8 TeV at the LHC, with ...integrated luminosities of up to 5.3 and 4.1 fb - 1 , respectively, are combined. No evidence for a heavy narrow resonance is observed. The analysis of the combined data sets excludes, at 95% confidence level, a Sequential Standard Model Z SSM a2 resonance lighter than 2590 GeV, a superstring-inspired Z I a2 lighter than 2260 GeV, and KaluzaaKlein gravitons lighter than 2390 (2030) GeV, assuming that the coupling parameter k / M A= Pl is 0.10 (0.05). These are the most stringent limits to date.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A measurement of W super(+)W super(-) production in pp collisions at ... is presented. The data were collected with the CMS ...detector at the LHC, and correspond to an integrated luminosity of 4.92 plus or minus 0.11 fb super(-1). The W super(+)W super(-) candidates consist of two oppositely charged leptons, electrons or muons, accompanied by large missing transverse energy. The W super(+)W super(-) production cross section is measured to be 52.4 plus or minus 2.0 (stat.) plus or minus 4.5 (syst.) plus or minus 1.2 (lum.) pb. This measurement is consistent with the standard model prediction of 47.0 plus or minus 2.0 pb at next-to-leading order. Stringent limits on the WW gamma and WWZ anomalous triple gauge-boson couplings are set.
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 protonaproton collisions at s = 7 TeV corresponding to 4.96 fb - 1 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.
An inclusive search for supersymmetric processes that produce final states with jets and missing transverse energy is performed in pp collisions at a centre-of-mass energy of 8 TeV. The data sample ...corresponds to an integrated luminosity of 11.7 fb super(-1) collected by the CMS experiment at the LHC. In this search, a dimensionless kinematic variable, alpha sub(T), is used to discriminate between events with genuine and misreconstructed missing transverse energy. The search is based on an examination of the number of reconstructed jets per event, the scalar sum of transverse energies of these jets, and the number of these jets identified as originating from bottom quarks. No significant excess of events over the standard model expectation is found. Exclusion limits are set in the parameter space of simplified models, with a special emphasis on both compressed-spectrum scenarios and direct or gluino-induced production of third-generation squarks. For the case of gluino-mediated squark production, gluino masses up to 950-1125 GeV are excluded depending on the assumed model. For the direct pair-production of squarks, masses up to 450 GeV are excluded for a single light first- or second-generation squark, increasing to 600 GeV for bottom squarks.
Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, ...including the transverse momenta ( ) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta ( ), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb super(-1). The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the distributions of the leading jets at high values, the distributions of the at high- and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.
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