Recursos de colección

Caltech Authors (157.532 recursos)

Repository of works by Caltech published authors.

Group = CMS@Caltech

Mostrando recursos 1 - 20 de 53

  1. Search for a heavy resonance decaying to a top quark and a vector-like top quark at √s = 13 TeV

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Bunn, J.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A search is presented for massive spin-1 Z′ resonances decaying to a top quark and a heavy vector-like top quark partner T. The search is based on a 2.6 fb^(−1) sample of proton-proton collisions at 13 TeV collected with the CMS detector at the LHC. The analysis is optimized for final states in which the T quark decays to a W boson and a bottom quark. The focus is on all-jet final states in which both the W boson and the top quark decay into quarks that evolve into jets. The decay products of the top quark and of the...

  2. Measurement of the tt production cross section using events with one lepton and at least one jet in pp collisions at √s = 13 TeV

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Bunn, J.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A measurement of the tt production cross section at √s = 13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.2 fb^(−1), collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be σ_(tt) = 888 ± 2,(stat)^(+26)_(−28)(syst)±20(lumi)pb, in agreement with...

  3. Measurement of the top quark mass using single top quark events in proton-proton collisions at √s = 8 TeV

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Bunn, J.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A measurement of the top quark mass is reported in events containing a single top quark produced via the electroweak t channel. The analysis is performed using data from proton-proton collisions collected with the CMS detector at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb^(−1). Top quark candidates are reconstructed from their decay to a W boson and a b quark, with the W boson decaying leptonically to a muon and a neutrino. The final state signature and kinematic properties of single top quark events in the t channel are used...

  4. Search for single production of vector-like quarks decaying to a Z boson and a top or a bottom quark in proton-proton collisions at √s = 13 TeV

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Bunn, J.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A search for single production of vector-like quarks, T and B, decaying into a Z boson and a top or a bottom quark, respectively, is presented. The search is performed using data collected by the CMS experiment at the LHC in proton-proton collisions at √s = 13 TeV, corresponding to an integrated luminosity of 2.3fb^(−1). An exotic T quark production mode through the decay of a heavy Z′ resonance is also considered. The search is performed in events with a Z boson decaying leptonically, accompanied by a bottom or a top quark decaying hadronically. No excess of events is observed...

  5. Measurement of electroweak-induced production of Wγ with two jets in pp collisions at √s = 8 TeV and constraints on anomalous quartic gauge couplings

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A measurement of electroweak-induced production of Wγ and two jets is performed, where the W boson decays leptonically. The data used in the analysis correspond to an integrated luminosity of 19.7 fb^(−1) collected by the CMS experiment in √s = 8 TeV proton-proton collisions produced at the LHC. Candidate events are selected with exactly one muon or electron, missing transverse momentum, one photon, and two jets with large rapidity separation. An excess over the hypothesis of the standard model without electroweak production of Wγ with two jets is observed with a significance of 2.7 standard deviations. The cross section measured...

  6. Search for new physics with dijet angular distributions in proton-proton collisions at √s = 13 TeV

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Bunn, J.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A search is presented for extra spatial dimensions, quantum black holes, and quark contact interactions in measurements of dijet angular distributions in proton-proton collisions at √s = 13 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 2.6 fb^(−1). The distributions are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Limits for different contact interaction models are obtained. In a benchmark model, valid to next-to-leading order in QCD and in which only left-handed quarks participate, quark contact interactions are excluded up to a...

  7. A search for new phenomena in pp collisions at √s = 13 TeV in final states with missing transverse momentum and at least one jet using the αT variable

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A search for new phenomena is performed in final states containing one or more jets and an imbalance in transverse momentum in pp collisions at a centre-of-mass energy of 13 TeV. The analysed data sample, recorded with the CMS detector at the CERN LHC, corresponds to an integrated luminosity of 2.3 fb^(−1). Several kinematic variables are employed to suppress the dominant background, multijet production, as well as to discriminate between other standard model and new physics processes. The search provides sensitivity to a broad range of new-physics models that yield a stable weakly interacting massive particle. The number of observed...

  8. Search for dark matter produced with an energetic jet or a hadronically decaying W or Z boson at √s = 13 TeV

    Sirunyan, A. M.; Anderson, D.; Bornheim, A.; Bunn, J.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A search for dark matter particles is performed using events with large missing transverse momentum, at least one energetic jet, and no leptons, in proton-proton collisions at √s = 13 TeV collected with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 12.9 fb^(−1) . The search includes events with jets from the hadronic decays of a W or Z boson. The data are found to be in agreement with the predicted background contributions from standard model processes. The results are presented in terms of simplified models in which dark matter particles are produced...

  9. Search for electroweak production of a vector-like quark decaying to a top quark and a Higgs boson using boosted topologies in fully hadronic final states

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Bunn, J.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A search is performed for electroweak production of a vector-like top quark partner T of charge 2/3 in association with a standard model top or bottom quark, using 2.3 fb^(−1) of proton-proton collision data at s√=13 TeV collected by the CMS experiment at the CERN LHC. The search targets T quarks decaying to a top quark and a Higgs boson in fully hadronic final states. For a T quark with mass above 1 TeV the daughter top quark and Higgs boson are highly Lorentz-boosted and can each appear as a single hadronic jet. Jet substructure and b tagging techniques are...

  10. Search for dark matter in proton-proton collisions at 8 TeV with missing transverse momentum and vector boson tagged jets

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A search is presented for an excess of events with large missing transverse momentum in association with at least one highly energetic jet, in a data sample of proton-proton collisions at a centre-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 fb^(−1) collected by the CMS experiment at the LHC. The results are interpreted using a set of simplified models for the production of dark matter via a scalar, pseudoscalar, vector, or axial vector mediator. Additional sensitivity is achieved by tagging events consistent with the jets originating from a hadronically decaying vector boson. This search...

  11. Measurement of the WZ production cross section in pp collisions at √s = 7 and 8 TeV and search for anomalous triple gauge couplings at √s = 8 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    The WZ production cross section is measured by the CMS experiment at the CERN LHC in proton-proton collision data samples corresponding to integrated luminosities of 4.9 fb^(−1) collected at √s = 7 TeV, and 19.6 fb^(−1) at √s = 8 TeV. The measurements are performed using the fully-leptonic WZ decay modes with electrons and muons in the final state. The measured cross sections for 71 < m_Z < 111 GeV are σ(pp → WZ; √s = 7 TeV) = 20.14 ± 1.32 (stat) ± 0.38 (theo) ± 1.06 (exp) ± 0.44 (lumi) pb and σ(pp → WZ; √s = 8...

  12. Observation of Y(1S) pair production in proton-proton collisions at √s = 8 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    Pair production of Y(1S) mesons is observed at the LHC in proton-proton collisions at √s = 8 TeV by the CMS experiment in a data sample corresponding to an integrated luminosity of 20.7 fb^(−1). Both Y(1S) candidates are fully reconstructed via their decays to μ^+μ^−. The fiducial acceptance region is defined by an absolute Y(1S) rapidity smaller than 2.0. The fiducial cross section for the production of Y(1S) pairs, assuming that both mesons decay isotropically, is measured to be 68.8±12.7 (stat)±7.4 (syst)±2.8 (B) pb, where the third uncertainty comes from the uncertainty in the branching fraction of Y(1S) decays to...

  13. Search for supersymmetry in multijet events with missing transverse momentum in proton-proton collisions at 13 TeV

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Lawhorn, J. M.; Nguyen, T.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhang, Z.; Zhu, R. Y.; Dubinin, M.
    A search for supersymmetry is presented based on multijet events with large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of √s = 13 TeV. The data, corresponding to an integrated luminosity of 35.9 fb^(−1), were collected with the CMS detector at the CERN LHC in 2016. The analysis utilizes four-dimensional exclusive search regions defined in terms of the number of jets, the number of tagged bottom quark jets, the scalar sum of jet transverse momenta, and the magnitude of the vector sum of jet transverse momenta. No evidence for a significant excess of events is observed...

  14. Suppression and azimuthal anisotropy of prompt and nonprompt J/ψ production in PbPb collisions at √(s_N N) = 2.76 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.
    The nuclear modification factor R_(AA) and the azimuthal anisotropy coefficient v_2 of prompt and nonprompt (i.e. those from decays of b hadrons) J/ψ mesons, measured from PbPb and pp collisions at √(s_NN) = 2.76 TeV at the LHC, are reported. The results are presented in several event centrality intervals and several kinematic regions, for transverse momenta p_T > 6.5 GeV/c and rapidity |y| < 2.4, extending down to p_T = 3 GeV/c in the 1.6 < |y| < 2.4 range. The v_2 of prompt J/ψ is found to be nonzero, but with no strong dependence on centrality, rapidity, or p_T...

  15. Charged-particle nuclear modification factors in PbPb and pPb collisions at √(s_N N) = 5.02 TeV

    Khachatryan, V.; Anderson, D.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.
    The spectra of charged particles produced within the pseudorapidity window |η| < 1 at √(s_N N) = 5.02 TeV are measured using 404 μb^(−1) of PbPb and 27.4 pb^(−1) of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0.5 < p_T < 400 GeV in pp and 0.7 < p_T < 400 GeV in PbPb collisions. The corresponding nuclear modification factor, R_AA, is measured in bins of collision centrality. The R_AA in the 5% most central collisions shows a maximal suppression by a factor of 7-8...

  16. Measurement of prompt and nonprompt J/ψ production in pp and pPb collisions at √sNN = 5.02 TeV

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Bunn, J.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.
    This paper reports the measurement of J/ψ meson production in proton–proton (pp) and proton–lead (pPb) collisions at a center-of-mass energy per nucleon pair of 5.02TeV by the CMS experiment at the LHC. The data samples used in the analysis correspond to integrated luminosities of 28pb^(−1) and 35nb^(−1) for pp and pPb collisions, respectively. Prompt and nonprompt J/ψ mesons, the latter produced in the decay of B hadrons, are measured in their dimuon decay channels. Differential cross sections are measured in the transverse momentum range of 2

  17. Search for Low Mass Vector Resonances Decaying to Quark-Antiquark Pairs in Proton-Proton Collisions at √s = 13 TeV

    Sirunyan, A. M.; Anderson, D.; Bendavid, J.; Bornheim, A.; Lawhorn, J. M.; Newman, H. B.; Nguyen, T.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhang, Z.; Zhu, R. Y.; Dubinin, M.
    A search is reported for a narrow vector resonance decaying to quark-antiquark pairs in proton-proton collisions at √s = 13 TeV, collected with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.7 fb^(−1). The vector resonance is produced at large transverse momenta, with its decay products merged into a single jet. The resulting signature is a peak over background in the distribution of the invariant mass of the jet. The results are interpreted in the framework of a leptophobic vector resonance and no evidence is found for such particles in the mass range...

  18. Measurement of the inclusive jet cross section in pp collisions at √s = 2.76 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    The double-differential inclusive jet cross section is measured as a function of jet transverse momentum p_T and absolute rapidity |y|, using proton-proton collision data collected with the CMS experiment at the LHC, at a center-of-mass energy of s√ = 2.76 TeV and corresponding to an integrated luminosity of 5.43 pb^(−1). Jets are reconstructed within the p_T range of 74 to 592 GeVand the rapidity range |y| < 3.0. The reconstructed jet spectrum is corrected for detector resolution. The measurements are compared to the theoretical prediction at next-to-leading-order QCD using different sets of parton distribution functions. This inclusive cross section measurement...

  19. Measurement of electroweak production of a W boson and two forward jets in proton-proton collisions at √s = 8 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    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^(−1). The measured fiducial cross section for W bosons decaying to electrons or muons and for pT^(j1)> 60 GeV, p^(Tj2)> 50 GeV, |η^j| < 4.7, and m_(jj)> 1000 GeV is 0.42 ± 0.04 (stat) ± 0.09 (syst) ± 0.01 (lumi) pb. This result is consistent with the standard model leading-order prediction of...

  20. Search for supersymmetry in events with one lepton and multiple jets in proton-proton collisions at √s = 13 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bendavid, J.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Lawhorn, J. M.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    A search for supersymmetry is performed in events with a single electron or muon in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of 2.3 fb^(−1). Several exclusive search regions are defined based on the number of jets and b-tagged jets, the scalar sum of the jet transverse momenta, and the scalar sum of the missing transverse momentum and the transverse momentum of the lepton. The observed event yields in data are consistent with the expected backgrounds from standard model processes. The...

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