66 research outputs found
Combination of the top-quark mass measurements from the Tevatron collider
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Combination of CDF and D0 results on the W boson mass and width
No full textThe results on the direct measurements of the W-boson mass and width, based on the data collected by the Tevatron experiments CDF and D{sup -} at Fermilab are summarized and combined. The CDF Run-0 (1988-1889) and Run-I (1992-1995) results have been re-averaged using the BLUE method and combined with Run-I D{sup -} results and the latest published results from CDF taken from the first period of Run-II (2001-2004). The results are corrected to have consistency between the parton distribution functions and electroweak parameters. The resulting Tevatron averages for the mass and total decay width of the W boson are: M{sub W} = 80432 {+-} 39 MeV and {Lambda}{sub W} = 2056 {+-} 62 MeV. The inclusion of a preliminary Run-II measurement of {Lambda}{sub W} from D{sup -}0 gives {Lambda}{sub W} = 2050 {+-} 58 MeV
2012 Update of the Combination of CDF and D0 Results for the Mass of the W Boson
No full textWe summarize and combine the results on the direct measurements of the mass of the W boson in data collected by the Tevatron experiments CDF and D0 at Fermilab. Earlier results from CDF Run-0 (1988-1989), D0 and CDF Run-I (1992-1995) and D0 results from 1 fb{sup -1} (2002-2006) of Run-II data are now combined with two new, high statistics Run-II measurements: a CDF measurement in both electron and muon channels using 2.2 fb{sup -1} of integrated luminosity collected between 2002 and 2007, and a D0 measurement in the electron channel using 4.3 fb{sup -1} collected between 2006 and 2009. As in previous combinations, the results are corrected for inconsistencies in parton distribution functions and assumptions about electroweak parameters used in the different analyses. The resulting Tevatron average for the mass of the W boson is M{sub W} = 80,387 {+-} 16 MeV and a new world average including data from LEP II is M{sub W} = 80,385 {+-} 15 MeV
Higgs Boson Studies at the Tevatron
No full textWe combine searches by the CDF and D0 Collaborations for the standard model Higgs boson with mass in the range 90--200 GeV produced in the gluon-gluon fusion, , , , and vector boson fusion processes, and decaying in the , , , , and modes. The data correspond to integrated luminosities of up to 10 fb and were collected at the Fermilab Tevatron in collisions at TeV. The searches are also interpreted in the context of fermiophobic and fourth generation models. We observe a significant excess of events in the mass range between 115 and 140 GeV/. The local significance corresponds to 3.0 standard deviations at GeV/, consistent with the mass of the Higgs boson observed at the LHC, and we expect a local significance of 1.9 standard deviations. We separately combine searches for , , , and . The observed signal strengths in all channels are consistent with the presence of a standard model Higgs boson with a mass of 125 GeV/
The Higgs boson in the Standard Model : theoretical constraints and a direct search in the WH channel at the Tevatron
No full textHüske NK. The Higgs boson in the Standard Model : theoretical constraints and a direct search in the WH channel at the Tevatron. Bielefeld (Germany): Bielefeld University; 2010.Le mécanisme de Higgs du Modèle Standard (SM) peut expliquer l'origine de la masse. Il prédit également l'existence d'une particule non encore observée, le boson de Higgs, dont la masse n'est pas prédite par la théorie. Le boson de Higgs est fortement lié à la validité du SM à hautes énergies. On explique les trois scénarios pour l'évolution du SM et leurs implications pour les théories de l'inflation cosmologique. Si la masse du boson de Higgs se situe dans une certaine gamme, le SM pourrait rester une théorie valide jusqu'à l'échelle de Planck. Si le couplage du boson de Higgs à la gravité n'est pas minimal, il peut également être la particule responsable de l'inflation cosmologique. Pour rechercher le boson de Higgs au Tevatron, la production associée avec un boson W est l'un des canaux les plus sensibles pour une masse inférieure à 130 GeV. On analyse 5,3 fb-1 de données D0-Tevatron, en recherchant un boson W qui se désintègre en un lepton et un neutrino. Le boson de Higgs se désintègre en deux quarks b qui forment des jets qui peuvent être identifiés par un b tagger de réseau de neurones. Une analyse multivariée est utilisée pour améliorer la sensibilité au signal. En l'absence d'un excès de signal dans la comparaison données et simulation, on calcule une limite sur le produit (section efficace) x (rapport d'embranchement) dans le canal WH de 0,533 pb à une masse de 115 GeV à 95 pour cent niveau de confiance. Cette limite correspond à un facteur de 4,1 de la prédiction SM. D'autres limites sont calculées pour les masses dans une gamme de 100 à 150 GeV par pas de 5 GeV. Ces résultats seront soumis pour publication et contribuent à la combinaison d'analyses Higgs au Tevatron.The Higgs mechanism of the Standard Model of particle physics provides a plausible and theoretically solid explanation for the origin of mass. It predicts at the same time the existence of a yet unobserved particle, the Higgs boson, with unknown mass from theory. The Higgs boson is strongly linked to the validity of the Standard Model at highest energies. This work outlines the three possible scenarios for the fate of the Standard Model at highest energies and their implications for theories of cosmological inflation. If the Higgs boson mass lies within a certain range the Standard Model could remain a valid theory up to the Planck scale. If in this case, the Higgs boson couples non-minimally to gravity, it could function as the particle responsible for cosmological inflation in the very early Universe.
A direct search for the Higgs boson could unveil its mass. The associated production of a Higgs boson with a W boson has the highest yields of production cross section times branching ratio in the region below 130 GeV at the Tevatron accelerator. We analyze a dataset of 5.3 fb^-1 of Tevatron data accumulated by the DØ experiment, searching for a W boson that decays into a lepton and a neutrino, of which the latter is accounted for by missing energy in the detector. The Higgs boson decays into two b quarks which then hadronize and form jets. These jets can be identified by a neural network b tagging method. A Random Forest multivariate technique is then used to improve signal sensitivity. In the absence of a signal excess in our final data to simulation comparison, we set a limit on the production cross section times branching ratio of the Higgs boson in the WH channel of 0.533 pb at a mass of 115 GeV at a 95 percent confidence level. This limit corresponds to a factor of 4.1 of the Standard Model prediction. Further limits are set for Higgs masses in a range of 100 - 150 GeV in steps of 5 GeV, the region where the WH channel is most sensitive. These results will be submitted for publication and contribute to the Tevatron combination of Higgs analyses
Precision Electroweak Measurements and Constraints on the Standard Model
No full textThis note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D{\O}at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the results obtained in high- interactions, and used to predict results in low- experiments, such as atomic parity violation, M{\o}ller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2007 are new combinations of results on the W-boson mass and width and the mass of the top quark
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Precision Electroweak Measurements and Constraints on the Standard Model
No full textThis note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D0 at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the combined set of results obtained in high-Q{sup 2} interactions, and used to predict results in low-Q{sup 2} experiments, such as atomic parity violation, Moeller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2008 are new combinations of results on the W-boson mass and the mass of the top quark
Measurement of W±Z production in proton-proton collisions at √s=7 TeV with the ATLAS detector
No full textA study of W ± Z production in proton-proton collisions at √s=7 TeV is presented using data corresponding to an integrated luminosity of 4.6 fb−1 collected with the ATLAS detector at the Large Hadron Collider in 2011. In total, 317 candidates, with a background expectation of 68±10 events, are observed in double-leptonic decay final states with electrons, muons and missing transverse momentum. The total cross-section is determined to be σtotWZ=19.0+1.4−1.3(stat.)±0.9(syst.)±0.4(lumi.) pb , consistent with the Standard Model expectation of 17.6+1.1−1.0 pb . Limits on anomalous triple gauge boson couplings are derived using the transverse momentum spectrum of Z bosons in the selected events. The cross-section is also presented as a function of Z boson transverse momentum and diboson invariant mass
Search for the Standard Model Higgs boson in the H → τ +τ - decay mode in √s = 7TeV pp collisions with ATLAS
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