Measurement of the WW production cross section with dilepton final states in p-pbar collisions at sqrt(s)=1.96 TeV and limits on anomalous trilinear gauge couplings
D0 Collaboration, V. Abazov
备注：
8 pages, 12 figures; updated to reflect published version
We provide the most precise measurement of the WW production cross section in p-pbar collisions to date at a center of mass energy of 1.96 TeV, and set limits on the associated trilinear gauge couplings. The WW->lvl'v (l,l'=e,mu) decay channels are analyzed in 1 fb^(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider. The measured cross section is sigma(p-pbar -> WW) = 11.5 +/- 2.1 (stat + syst) +/- 0.7 (lumi) pb. One- and two-dimensional 95% C.L. limits on trilinear gauge couplings are provided.
Limits are set on anomalous WWgamma and WWZ trilinear gauge couplings using W+W- -> e+e-, W+W- -> e mu, and W+W- -> mu+mu- events. The data set was collected by the Run II D0 detector at the Fermilab Tevatron Collider and corresponds to approximately 250 inverse pb of integrated luminosity at sqrt(s) = 1.96 TeV. Under the assumption that the WWgamma couplings are equal to the WWZ couplings and using a form factor scale of Lambda = 2.0 TeV, the combined 95% C.L. one-dimensional coupling limits from all three channels are -0.32 < Delta kappa < 0.45 and -0.29 < lambda < 0.30.
We present results of the first search for like-sign dilepton (ee, eμ, μμ) events associated with multijets and large missing energy using 106 pb^-1 of data in p-pbar collisions at sqrt(s)=1.8 TeV collected during 1992-95 by the CDF experiment. Finding no events that pass our selection, we examine pair-production of gluinos and squarks in a constrained framework of the Minimal Supersymmetric Standard Model. At tan_beta = 2 and μ=-800 GeV/c^2, we set 95% confidence level limits of M(gluino) > 221 GeV/c^2 for M(gluino) \simeq M(squark), and M(gluino) > 168 GeV/c^2 for M(squark) \gg M(gluino), bo…
We present measurements of the anomalous WWgamma and WWZ trilinear gauge couplings from a combination of four diboson production and decay channels using data collected by the D0 detector at the Fermilab Tevatron Collider. These results represent the first high statistics combination of limits across different diboson production processes at the Tevatron and use data corresponding to an integrated luminosity of approximately 1 fb^-1. When respecting SU(2)_L x U(1)_Y symmetry, we measure central values and 68% C.L. allowed intervals of kappa_gamma=1.07^+0.16_-0.20, lambda =0.00^+0.05_-0.04 and …
A search for the standard model Higgs boson is presented using events with two charged leptons and large missing transverse energy selected from 5.4 fb-1 of integrated luminosity in p-pbar collisions at sqrt(s)=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess of events above background predictions is found, and observed (expected) upper limits at 95% confidence level on the rate of Higgs boson production are derived that are a factor of 1.55 (1.36) above the predicted standard model cross section at Higgs boson mass of 165 GeV.
We have searched for the supersymmetric partner of the top quark (stop) in 107 pb^{-1} of p-pbar collisions at \sqrt{s}= 1.8 TeV collected by the Collider Detector at Fermilab (CDF). Within the framework of the Minimal Supersymmetric extension of the Standard Model (MSSM) each of the pair-produced stops is assumed to decay into a lepton, bottom quark and supersymmetric neutrino. Such a scenario would give rise to events with two leptons, two hadronic jets, and a substantial imbalance of transverse energy. No evidence of such a stop signal has been found. We calculate a 95% confidence level (C.…
This paper reports a measurement of the cross section for the pair production of top quarks in ppbar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron. The data was collected from the CDF II detector in a set of runs with a total integrated luminosity of 1.1 fb^{-1}. The cross section is measured in the dilepton channel, the subset of ttbar events in which both top quarks decay through t -> Wb -> l nu b where l = e, mu, or tau. The lepton pair is reconstructed as one identified electron or muon and one isolated track. The use of an isolated track to identify the second lepton increases…
We propose a like-sign dilepton search for chargino-neutralino production in p-pbar collisions at sqrt(s) = 1.8 TeV, which complements the previously published trilepton search by the CDF detector using Fermilab Run I data. Monte Carlo predictions for the signal and background efficiencies indicate a significant increase in sensitivity to chargino-neutralino production compared to the traditional trilepton analysis alone.
A search for new particles (X) that decay to electron or muon pairs has been performed using approximately 200 pb**(-1) of pbarp collision data at sqrt(s)=1.96 TeV collected by the CDF II experiment at the Fermilab Tevatron. Limits on sigma(ppbar -> X)*BR(X -> ll) are presented as a function of dilepton invariant mass m(ll) > 150 GeV/c**2, for different spin hypotheses (0, 1, or 2). The limits are approximately 25 fb for m(ll) > 600 GeV/c**2. Lower mass bounds for X from representative models beyond the Standard Model including heavy neutral gauge bosons are presented.
We present evidence for dilepton events from t tbar production with one electron or muon and one hadronically decaying tau lepton from the decay t tbar -> (l nu_l) (tau nu_tau) b bbar, (l=e, mu), using the Collider Detector at Fermilab (CDF). In a 109 pb^-1 data sample of p pbar collisions at sqrt(s) = 1.8 TeV we expect ~1 signal event and a total background of ~2 events; we observe 4 candidate events (2 e tau and 2 mu tau). Three of these events have jets identified as b candidates, compared to an estimated background of 0.28+-0.02 events.
We present a measurement of the ttbar production cross section in ppbar collisions at root(s) = 1.8TeV by the D0 experiment at the Fermilab Tevatron. The measurement is based on data from an integrated luminosity of approximately 125 pb^-1 accumulated during the 1992-1996 collider run. We observe 39 ttbar candidate events in the dilepton and lepton+jets decay channels with an expected background of 13.7+-2.2 events. For a top quark mass of 173.3GeV/c^2, we measure the ttbar production cross section to be 5.5+-1.8 pb.
The D0 collaboration has performed a measurement of the top quark mass based on six candidate events for the process t tbar -> b W+ bbar W-, where the W bosons decay to e nu or mu nu. This sample was collected during an exposure of the D0 detector to an integrated luminosity of 125 pb^-1 of sqrt(s)=1.8 TeV p-pbar collisions. We obtain mt = 168.4 +- 12.3 (stat) +- 3.7 (sys) GeV/c^2, consistent with the measurement obtained using single-lepton events. Combination of the single-lepton and dilepton results yields mt = 172.0 +- 7.5 GeV/c^2.
We present a search for exclusive Z boson production in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using the CDF II detector at Fermilab. We observe no exclusive Z->ll candidates and place the first upper limit on the exclusive Z cross section in hadron collisions, sigma(exclu) < 0.96 pb at 95% confidence level. In addition, we observe eight candidate exclusive dilepton events from the quantum electrodynamic process ppbar->gammagamma->p+ll+pbar, and measure the cross section for M(ll) > 40 GeV/c2 and |eta(l)| < 4 to be sigma = 0.24^{+0.13}_{-0.10} pb, which is the first measurement fo…
The production rate and kinematics of photons produced in association with Z bosons are studied using 2/fb of p\bar{p} collision data collected at the Collider Detector at Fermilab. The cross section for p\bar{p} -> l^+ l^- gamma + X (where the leptons l are either muons or electrons with dilepton mass M_{ll} > 40 GeV/c^2, and where the photon has transverse energy Et_{gamma} > 7 GeV and is well separated from the leptons) is 4.6 +/- 0.2 (stat) +/- 0.3 (syst) +/- 0.3 (lum) pb, which is consistent with standard model expectations. We use the photon Et distribution from Z-gamma events where the …
We report a measurement of the top quark mass using six candidate events for the process pbarp->ttbar->l^+ nu l^- nubar b bbar + X, observed in the D0 experiment at the Fermilab ppbar collider. Using maximum likelihood fits to the dynamics of the decays, we measure a mass for the top quark of m(top) = 168.4 +- 12.3 (stat) +- 3.6 (syst) GeV/c^2. We combine this result with our previous measurement in the ttbar->l+jets channel to obtain m(top) = 172.1 +- 7.1 GeV/c^2 as the best value of the mass of the top quark measured by D0.
We present measurements of the top quark mass using the \mT2, a variable related to the transverse mass in events with two missing particles. We use the template method applied to t\tbar dilepton events produced in p\pbar collisions at Fermilab's Tevatron and collected by the CDF detector. From a data sample corresponding to an integrated luminosity of 3.4 \invfb, we select 236 t\tbar candidate events. Using the \mT2 distribution, we measure the top quark mass to be M_{Top} = 168.0^{+4.8}_{-4.0} $\pm$ {2.9} GeV/c^{2}. By combining the \mT2 with the reconstructed top mass distributions based on…
We present a search for associated Higgs boson production in the process pbar -> W/ZH -> l\pml'\pm + X in ee, eμ, and μμ final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at sqrt{s} = 1.96 TeV corresponding to 5.3 fb-1 of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C.L. observed (expected) upper limits on ratio of the production cross section to the standard model expectat…
We present electroweak physics results from the DZero experiment using data from collisions at \sqrt{s} = 1.8 TeV, concentrating on single W and Z production cross sections and the production of electroweak gauge boson pairs. The inclusive cross sections times branching ratios for W and Z production have been measured and are used to determine the inclusive width of the W boson. Direct tests of the WWγand WWZ trilinear gauge boson couplings are derived from the study of diboson production. These measurements test the non-abelian self couplings of the W, Z and photon, one of the most direct con…
The gauge boson pair production processes Wg, WW, WZ, and Zg were studied using pbarp collisions corresponding to an integrated luminosity of ~14 pb-1 at a center-of-mass energy of sqrt(s) = 1.8 TeV. Analysis of Wg prod with subsequent W boson decay to lv (l=e,mu) is reported, including a fit to the pT spectrum of the photons which leads to limits on anomalous WWg couplings. A search for WW prod with subsequent decay to l-lbar-v-vbar (l=e,mu) is presented leading to an upper limit on the WW prod cross section and limits on anomalous WWg and WWZ couplings. A search for high pT W bosons in WW an…
We report the first measurements of inclusive W and Z boson cross sections times the corresponding leptonic branching ratios for p pbar collisions at sqrt{s} = 1.96 TeV based on the decays of the W and Z bosons into electrons and muons. The data were recorded with the CDF II detector at the Fermilab Tevatron and correspond to an integrated luminosity of 72.0 +/- 4.3 pb-1. We test e-mu lepton universality in W decays by measuring the ratio of the W->mu nu to W->e nu cross sections and determine a value of 0.991 +/- 0.004(stat.) +/- 0.011(syst.) for the ratio of W-l-nu couplings (g_mu/g_e). Sinc…
Recent results on top quark physics with the D0 experiment in pbar-p collisions at sqrt(s) = 1.8 TeV for an integrated luminosity of 125 pb**-1 are reported. The direct measurement of the top quark mass uses single lepton and dilepton events, giving the result m(top) = 172.1 +/- 7.1 GeV/c**2. The measurement of the t-tbar production cross section includes analyses from 9 top decay channels: dilepton (t-tbar --> e+mu, e+e, and mu+mu), electron and neutrino (t-tbar --> e+nu), single leptons (t-tbar --> e + jets, t-tbar --> mu + jets) with and without b tagging, and all-jets (t-tbar --> 6 jets). …
We present a measurement of the top quark mass with t-tbar dilepton events produced in p-pbar collisions at the Fermilab Tevatron $\sqrt{s}$=1.96 TeV and collected by the CDF II detector. A sample of 328 events with a charged electron or muon and an isolated track, corresponding to an integrated luminosity of 2.9 fb$^{-1}$, are selected as t-tbar candidates. To account for the unconstrained event kinematics, we scan over the phase space of the azimuthal angles ($ϕ_{ν_1},ϕ_{ν_2}$) of neutrinos and reconstruct the top quark mass for each $ϕ_{ν_1},ϕ_{ν_2}$ pair by minimizing a $χ^2$ function in t…
Direct measurements of the trilinear gauge boson couplings by the CDF and D0 collaborations at Fermilab are reviewed. Limits on the anomalous couplings were obtained at a 95 % CL from four diboson production processes: W-gamma production with the subsequent W boson decay to e-nu or mu-nu, WW production with both the W boson decaying to e-nu or mu-nu, WW/WZ production with one of the gauge bosons decaying leptonically and the other gauge boson decaying to two jets, and Z-gamma production with the subsequent Z boson decay to e-e, mu-mu, or nu-nu. Limits were also obtained by a combined fit to W-…
A measurement of W-gamma and Z-gamma production in proton-proton collisions at sqrt(s) = 7 TeV is presented. Results are based on a data sample recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 36 inverse picobarns. The electron and muon decay channels of the W and Z are used. The total cross sections are measured for photon transverse energy >10 GeV and spatial separation from charged leptons in the plane of pseudorapidity and azimuthal angle >0.7, and with an additional dilepton invariant mass requirement of > 50 GeV for the Z-gamma process. The followin…
