123 research outputs found

    A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer

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    A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp → pp + Z/γ + X, in proton-tagged events from proton–proton collisions at √s = 13 TeV, recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600–1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. odelindependent upper limits on the visible production cross section of pp → pp + Z/γ + X are set

    Search for standard-model Z and Higgs bosons decaying into a bottom-antibottom quark pair in proton-antiproton collisions at 1.96 TeV

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    The Collider Detector at Fermilab collected a unique sample of jets originating from bottom-quark fragmentation (b-jets) by selecting online proton-antiproton (pp̄) collisions with a vertex displaced from the pp̄ interaction point, consistent with the decay of a bottom-quark hadron. This data set, collected at a center-of-mass energy of 1.96 TeV, and corresponding to an integrated luminosity of 5.4 fb-1, is used to measure the Z-boson production cross section times branching ratio into bb̄. The number of Z→bb̄ events is determined by fitting the dijet-mass distribution, while constraining the dominant b-jet background, originating from QCD multijet events, with data. The result, σ(pp̄→Z)×B(Z→bb̄)=1.11±0.08(stat)±0.14(syst) nb, is the most precise measurement of this process, and is consistent with the standard-model prediction. The data set is also used to search for Higgs-boson production. No significant signal is expected in our data and the first upper limit on the cross section for the inclusive pp̄→H→bb̄ process at s=1.96 TeV is set, corresponding to 33 times the expected standard-model cross section, or σ=40.6 pb, at the 95% confidence level

    Search for the Exotic Meson X(5568) with the Collider Detector at Fermilab

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    A search for the exotic meson X(5568) decaying into the B[subscript s][superscript 0]π[superscript ±] final state is performed using data corresponding to 9.6  fb[superscript -1] from pp[over ¯] collisions at sqrt[s]=1960  GeV recorded by the Collider Detector at Fermilab. No evidence for this state is found and an upper limit of 6.7% at the 95% confidence level is set on the fraction of B[subscript s][superscript 0] produced through the X(5568)→B[subscript s][superscript 0]π[superscript ±} process

    Search for standard-model Z and Higgs bosons decaying into a bottom-antibottom quark pair in proton-antiproton collisions at 1.96 TeV

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    The Collider Detector at Fermilab collected a unique sample of jets originating from bottom-quark fragmentation (b-jets) by selecting online proton-antiproton (p[¯ over p]) collisions with a vertex displaced from the p[¯ over p] interaction point, consistent with the decay of a bottom-quark hadron. This data set, collected at a center-of-mass energy of 1.96 TeV, and corresponding to an integrated luminosity of 5.4  fb[superscript -1], is used to measure the Z-boson production cross section times branching ratio into b[¯ over b]. The number of Z→b[¯ over b] events is determined by fitting the dijet-mass distribution, while constraining the dominant b-jet background, originating from QCD multijet events, with data. The result, σ(p[¯ over p]→Z)×B(Z→b[¯ over b])=1.11 ± 0.08(stat) ± 0.14(syst)  nb, is the most precise measurement of this process, and is consistent with the standard-model prediction. The data set is also used to search for Higgs-boson production. No significant signal is expected in our data and the first upper limit on the cross section for the inclusive p[¯ over p]→H→b[¯ over b] process at √s=1.96  TeV is set, corresponding to 33 times the expected standard-model cross section, or σ=40.6  pb, at the 95% confidence level.National Science Foundation (U.S.)United States. Department of EnergyAlfred P. Sloan Foundatio

    Search for the Exotic Meson X(5568) with the Collider Detector at Fermilab

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    A search for the exotic meson X(5568) decaying into the Bs0π± final state is performed using data corresponding to 9.6 fb-1 from pp̄ collisions at s=1960 GeV recorded by the Collider Detector at Fermilab. No evidence for this state is found and an upper limit of 6.7% at the 95% confidence level is set on the fraction of Bs0 produced through the X(5568)→Bs0π± process

    Tevatron Run II combination of the effective leptonic electroweak mixing angle

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    Drell-Yan lepton pairs produced in the process pp→â.,"+â.,"-+X through an intermediate γ∗/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin2θefflept using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9-10 fb-1 of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin2θefflept=0.23148±0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin2θW, or equivalently the W-boson mass MW, using the zfitter software package yields sin2θW=0.22324±0.00033 or equivalently, MW=80.367±0.017 GeV/c2

    Measurement of the production and differential cross sections of W+W- bosons in association with jets in p(p)over-bar collisions at root s = 1.96 TeV (vol 91, 111101, 2015)

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    Observation of charge-ordering in particle production in hadronic Z(0) decay

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    Analysis of the rapidity structure of charge correlations in hadronic events from Z(0) decays gives evidence for chain-like charge-ordering of particle production along the thrust axis, as predicted by ‘QCD-motivated’ string-like fragmentation models. (C) 1997 Published by Elsevier Science B.V

    OBSERVATION OF SHORT-RANGE 3-PARTICLE CORRELATIONS IN E(+)E(-) ANNIHILATIONS AT LEP ENERGIES

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    Measurements are presented of short range three-particle correlations in e(+)e(-) annihilations at LEP using data collected by the DELPHI detector. At small values of the four-momentum difference, strong three-particle correlations are observed for like-sign (+++ and —) and for unlike-sign (++- and +–) pion combinations which are not a consequence of two-particle correlations. A possible explanation of the observed effects in like-sign combinations is the existence of higher order Bose-Einstein interference, which significantly changes the particle distributions in jets

    Determination of the average lifetime of b-baryons

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    The average lifetime of b-baryons has been studied using 3 x 10(6) hadronic Z(0) decays collected by the DELPHI detector at LEP. Three methods have been used, based on the measurement of different observables: the proper decay time distribution of 206 vertices reconstructed with a Lambda, a lepton and an oppositely charged pion; the impact parameter distribution of 441 muons with high transverse momentum accompanied by a Lambda in the same jet; and the proper decay time distribution of 125 Lambda(c)-lepton decay vertices with the Lambda(c) exclusively reconstructed through its pK pi, pK(0) and Lambda 3 pi decay modes. The combined result is: [GRAPHICS] where the first systematic error is due to experimental uncertainties and the second to the uncertainties in the modelling of the b-baryon production and semi-leptonic decay, Including the measurement recently published by DELPHI based on a sample of proton-muon vertices, the average b-baryon lifetime is: [GRAPHICS] [GRAPHICS
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