A measurement is presented of the cross section for the electroweak production of a W boson in association with two jets in proton-proton collisions at a center-of-mass energy of 8 TeV. The data set ...was collected with the CMS detector and corresponds to an integrated luminosity of 19.3 fb super(-1). The measured fiducial cross section for W bosons decaying to electrons or muons and for p sub(T) super(j1) > 60 GeV, p sub(T) super(j2) > 50 GeV, | eta super(j)| < 4.7, and m sub(jj) > 1000 GeV is 0.42 plus or minus 0.04 (stat) plus or minus 0.09 (syst) plus or minus 0.01 (lumi) pb. This result is consistent with the standard model leading-order prediction of 0.50 plus or minus 0.02 (scale) plus or minus 0.02 (PDF) pb obtained with MadGraph5_amclo 2.1 interfaced to pythia 6.4. This is the first cross section measurement for this process. Figure not available: see fulltext.
A search is presented for single top quark production in the s channel in proton-proton collisions with the CMS detector at the CERN LHC in decay modes of the top quark containing a muon or an ...electron in the final state. The signal is extracted through a maximum-likelihood fit to the distribution of a multivariate discriminant defined using boosted decision trees to separate the expected signal contribution from background processes. The analysis uses data collected at centre-of-mass energies of 7 and 8 TeV and corresponding to integrated luminosities of 5.1 and 19.7 fb super(-1), respectively. The measured cross sections of 7.1 plus or minus 8.1 pb (at 7 TeV) and 13.4 plus or minus 7.3 pb (at 8 TeV) result in a best fit value of 2.0 plus or minus 0.9 for the combined ratio of the measured and expected values. The signal significance is 2.5 standard deviations, and the upper limit on the rate relative to the standard model expectation is 4.7 at 95% confidence level. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A search for exclusive or quasi-exclusive gamma gamma arrow right W super(+) W super(-) production, via pp arrow right p ...super((*)) W super(+) W super(-) p super((*)) arrow right p super((*)) mu super( plus or minus )e super() p super((*)) at ... TeV, is reported using data corresponding to an integrated luminosity of 19.7 fb super(-1). Events are selected by requiring the presence of an electron-muon pair with large transverse momentum p sub(T)( mu super( plus or minus )e super()) > 30 GeV, and no associated charged particles detected from the same vertex. The 8 TeV results are combined with the previous 7 TeV results (obtained for 5.05 fb super(-1) of data). In the signal region, 13 (2) events are observed over an expected background of 3.9 plus or minus 0.6 (0.84 plus or minus 0.15) events for 8 (7) TeV, resulting in a combined excess of 3.4 sigma over the background-only hypothesis. The observed yields and kinematic distributions are compatible with the standard model prediction for exclusive and quasi-exclusive gamma gamma arrow right W super(+) W super(-) production. Upper limits on the anomalous quartic gauge coupling operators a sub(0,)C super( )W(dimension-6) and f sub( )M,1,2,3(dimension-8), the most stringent to date, are derived from the measured dilepton transverse momentum spectrum. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The decorrelation in the azimuthal angle between the most forward and the most backward jets (Mueller-Navelet jets) is ...measured in data collected in pp collisions with the CMS detector at the LHC at ... TeV. The measurement is presented in the form of distributions of azimuthal-angle differences, Delta , between the Mueller-Navelet jets, the average cosines of ( pi - Delta ), 2( pi - Delta ), and 3( pi - Delta ), and ratios of these cosines. The jets are required to have transverse momenta, p sub(T), in excess of 35 GeV and rapidities, |y|, of less than 4.7. The results are presented as a function of the rapidity separation, Delta y, between the Mueller-Navelet jets, reaching Delta y up to 9.4 for the first time. The results are compared to predictions of various Monte Carlo event generators and to analytical predictions based on the DGLAP and BFKL parton evolution schemes. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).are reported from a search for the top squark ..., the lighter of the two supersymmetric partners of the top quark. The ...data sample corresponds to 19.7 fb super(-1) of proton-proton collisions at ... TeV collected with the CMS detector at the LHC. The search targets ... and ... decay modes, where ... and ... are the lightest chargino and neutralino, respectively. The reconstructed final state consists of jets, b jets, missing transverse energy, and either one or two leptons. Leading backgrounds are determined from data. No significant excess in data is observed above the expectation from standard model processes. The results exclude a region of the two-dimensional plane of possible ... and ... masses. The highest excluded ... and ... masses are about 700 GeV and 250 GeV, respectively. Figure not available: see fulltext.
This paper presents the search for the production of a Higgs boson in association with a single top quark (tHq), using data collected in proton-proton collisions at a center-of-mass energy of 8 TeV ...corresponding to an integrated luminosity of 19.7 fb super(-1). The search exploits a variety of Higgs boson decay modes resulting in final states with photons, bottom quarks, and multiple charged leptons, including tau leptons, and employs a variety of multivariate techniques to maximize sensitivity to the signal. The analysis is optimized for the opposite sign of the Yukawa coupling to that in the standard model, corresponding to a large enhancement of the signal cross section. In the absence of an excess of candidate signal events over the background predictions, 95% confidence level observed (expected) upper limits on anomalous tHq production are set, ranging between 600 (450) fb and 1000 (700) fb depending on the assumed diphoton branching fraction of the Higgs boson. This is the first time that results on anomalous tHq production have been reported. Figure not available: see fulltext.
The result of a search for flavor changing neutral currents (FCNC) through single top quark production in association with a photon is presented. The study is based on proton-proton collisions at a ...center-of-mass energy of 8 TeV using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 fb super(-1). The search for t gamma events where t arrow right Wb and W arrow right mu nu is conducted in final states with a muon, a photon, at least one hadronic jet with at most one being consistent with originating from a bottom quark, and missing transverse momentum. No evidence of single top quark production in association with a photon through a FCNC is observed. Upper limits at the 95% confidence level are set on the tu gamma and tc gamma anomalous couplings and translated into upper limits on the branching fraction of the FCNC top quark decays: (t arrow right u gamma )<1.310 super(-4) and (t arrow right c gamma )<1.710 super(-3). Upper limits are also set on the cross section of associated t gamma production in a restricted phase-space region. These are the most stringent limits currently available. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A search for compositeness of electrons and muons is presented using a data sample of proton-proton collisions at a ...center-of-mass energy of ... TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb super(-1). Excited leptons ( super(*)) produced via contact interactions in conjunction with a standard model lepton are considered, and a search is made for their gauge decay modes. The decays considered are super(*) arrow right gamma and super(*) arrow right Z, which give final states of two leptons and a photon or, depending on the Z-boson decay mode, four leptons or two leptons and two jets. The number of events observed in data is consistent with the standard model prediction. Exclusion limits are set on the excited lepton mass, and the compositeness scale Lambda . For the case M sub( )= Lambda the existence of excited electrons (muons) is excluded up to masses of 2.45 (2.47) TeV at 95% confidence level. Neutral current decays of excited leptons are considered for the first time, and limits are extended to include the possibility that the weight factors f and f', which determine the couplings between standard model leptons and excited leptons via gauge mediated interactions, have opposite sign. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A search for a very light Higgs boson decaying into a pair of tau leptons is presented within the framework of the ...next-to-minimal supersymmetric standard model. This search is based on a data set corresponding to an integrated luminosity of 19.7 fb super(-1) of proton-proton collisions collected by the CMS experiment at a centre-of-mass energy of 8 TeV. The signal is defined by the production of either of the two lightest scalars, h sub(1) or h sub(2), via gluon-gluon fusion and subsequent decay into a pair of the lightest Higgs bosons, a sub(1) or h sub(1). The h sub(1) or h sub(2) boson is identified with the observed state at a mass of 125 GeV. The analysis searches for decays of the a sub(1) (h sub(1)) states into pairs of tau leptons and covers a mass range for the a sub(1) (h sub(1)) boson of 4 to 8 GeV. The search reveals no significant excess in data above standard model background expectations, and an upper limit is set on the signal production cross section times branching fraction as a function of the a sub(1) (h sub(1)) boson mass. The 95% confidence level limit ranges from 4.5 pb at ... ... GeV to 10.3 pb at ... ... GeV. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 ...TeV pp collision data corresponding to an integrated luminosity of 19.5 fb super(-1), collected by the CMS experiment at the LHC. Final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from ... or ... decays. The ... cross section is measured to be 382 sub(-102) super(+117) fb with a significance of 4.8 standard deviations from the background-only hypothesis. The ... cross section is measured to be 242 sub(-55) super(+65) fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the ... and ... cross sections. Figure not available: see fulltext.
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