Direct measurement of the W boson width in p&pmacr; collisions at radicals = 1.8 TeV

This Letter describes a direct measurement of the W boson total decay width, gamma(W), using the Collider Detector at Fermilab. The measurement uses an integrated luminosity of 90 pb(-1), collected during the 1994-1995 run of the Fermilab Tevatron p&pmacr; collider. The width is determined by normalizing predicted signal and background distributions to 49 844 W-->enu candidates and 21 806 W-->&mgr;nu candidates in the transverse-mass region M(T)<200 GeV and then fitting the predicted shape to the 438 electron events and 196 muon events in the high- M(T) region, 100相似文献   

Measurement of the W-->taunu production cross section in pp collisions at square root s=1.8 TeV

We report on a measurement of sigma(pp-->W+X)B(W-->taunu) in pp collisions at sqrt[s]=1.8 TeV at the Fermilab Tevatron. The measurement is based on an integrated luminosity (lum) of 18 pb-1 of data collected with the D0 detector during 1994-1995. We find that sigma(pp-->W+X)B(W-->taunu)=2.22+/-0.09 (stat)+/-0. 10 (syst)+/-0.10 (lum) nb. Lepton universality predicts that the ratio of the tau and electron electroweak charged current couplings to the W boson, gWtau/gWe, be unity. We find gWtau/gWe=0.980+/-0.031, in agreement with lepton universality.     

Measurement of the W boson mass with the D0 detector

We present a measurement of the W boson mass using data corresponding to 4.3 fb(-1) of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron pp collider. With a sample of 1,677,394 W → eν candidate events, we measure M(W) = 80.367 ± 0.026 GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1 fb(-1) of integrated luminosity, to yield M(W) = 80.375 ± 0.023 GeV.     

Precision top-quark mass measurement in the lepton+jets topology in p p collisions at square root s=1.96 TeV

We report two measurements of the top-quark mass M(top) using the CDF II detector at the Fermilab Tevatron in a 318 pb(-1) data sample of tt events in the lepton+jets final state. One method uses an event-based likelihood technique resulting in M(top) = 173.2(-2.4)(+2.6)(stat) +/- 3.2(syst) GeV/c2 or 173.2(-4.0)(+4.1) GeV/c2. The second method reconstructs a top-quark mass in each event using the measured invariant mass of the hadronically decaying W boson to constrain the jet energy scale to obtain a value for M(top)of 173.5(-3.6)(+3.7)(stat) +/- 1.3(syst) GeV/c2 or 173.5(-3.8)(+3.9) GeV/c2 . We take the latter, which is more precise, as our result.     

Direct measurement of the W Boson width in ppover collisions at square roots = 1.96 TeV

A direct measurement of the total decay width of the W boson Gamma(W) is presented using 350 pb(-1) of data from pp[over ] collisions at square root s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The width is determined by normalizing predicted signal and background distributions to 230 185 W candidates decaying to enu and micronu in the transverse-mass region 50相似文献   

Measurement of d sigma/dM and forward-backward charge asymmetry for high-mass Drell-Yan e(+)e(-) pairs from pp macro collisions at square root of s = 1.8 TeV

We report on a measurement of the mass dependence of the forward-backward charge asymmetry, A(FB), and production cross section d sigma/dM for e(+)e(-) pairs with mass M(ee)>40 GeV/c(2). The data sample consists of 108 pb(-1) of pp macro collisions at square root of s = 1.8 TeV taken by the Collider Detector at Fermilab during 1992-1995. The measured asymmetry and d sigma/dM are compared with the predictions of the standard model and a model with an extra Z' gauge boson.     

Precise measurement of the top-quark mass in the lepton+jets topology at CDF II

We present a measurement of the mass of the top quark from proton-antiproton collisions recorded at the CDF experiment in Run II of the Fermilab Tevatron. We analyze events from the single lepton plus jets final state (tt-->W(+)bW(-)b-->lnubqq'b). The top-quark mass is extracted using a direct calculation of the probability density that each event corresponds to the tt final state. The probability is a function of both the mass of the top quark and the energy scale of the calorimeter jets, which is constrained in situ by the hadronic W boson mass. Using 167 events observed in 955 pb(-1) of integrated luminosity, we achieve the single most precise measurement of the top-quark mass, 170.8+/-2.2(stat.)+/-1.4(syst.) GeV/c(2).     

Measuring the top Yukawa coupling to a heavy Higgs Boson at future e(+)e(-) linear colliders

If the Higgs boson mass is greater than 350 GeV, the top quark Yukawa coupling can be determined using the Higgs resonant contribution to t&tmacr; production from W+W- fusion at high energy e(+)e(-) linear colliders. We have evaluated the significance with which the signal of a Higgs decaying to t&tmacr; pairs could be observed at future e(+)e(-) colliders, with center of mass energies of 800 GeV and 1 TeV, and an integrated luminosity of 1 ab(-1). We find that a signal significance greater than 5sigma and a relative error in the top Yukawa measurement better than 10% can be achieved at these facilities, for Higgs boson masses in the ranges of 350-500 GeV and 350-650 GeV, respectively.     

Search for Higgs bosons decaying to bb and produced in association with W bosons in pp collisions at square root of s = 1.96 TeV

We present a search for Higgs bosons decaying into bb and produced in association with W bosons in pp collisions at square root of s = 1.96 TeV. This search uses 320 pb(-1) of the data set accumulated by the upgraded Collider Detector at Fermilab. Events are selected that have a high-transverse momentum electron or muon, missing transverse energy, and two jets, at least one of which is consistent with the hadronization of a b quark. Both the number of events and the dijet mass distribution are consistent with standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson or any new particle with similar decay kinematics. These upper limits range from 10 pb for mH = 110 GeV/c2 to 3 pb for mH = 150 GeV/c2.     

Search for the Higgs boson in events with missing transverse energy and b quark jets produced in pp collisions at square root(s)=1.96 TeV

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use approximately 1 fb(-1) integrated luminosity of pp collisions at square root(s)=1.96 TeV recorded by the Collider Detector at Fermilab II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248+/-43 (14.4+/-2.7) are expected from standard model background processes. We observe no significant excess over the expected background and thus set 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 to 140 GeV/c(2). For a mass of 115 GeV/c(2), the observed (expected) limit is 20.4 (14.2) times the standard model prediction.     

Complete two loop bosonic contributions to the muon lifetime in the standard model

The last missing correction to the muon lifetime in the standard model at O(alpha(2)) coming from gauge and Higgs boson loops is presented. The associated contribution to the parameter Deltar in the on-shell scheme ranges from 6x10(-5) to -4x10(-5) for Higgs boson masses from 100 GeV to 1 TeV. This result translates into a shift of the W boson mass which does not exceed +/-1 MeV in the same range and amounts, in particular, to approximately -0.8 MeV for a 115 GeV Higgs boson.     

Search for a W' boson via the decay mode W'-->munumu in 1.8 TeV pp collisions

We report the results of a search for a W' boson produced in pp collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample recorded by the Collider Detector at Fermilab. We consider the decay channel W'-->&munumu and search for anomalous production of high transverse mass munumu lepton pairs. We observe no excess of events above background and set limits on the rate of W' boson production and decay relative to standard model W boson production and decay using a fit of the transverse mass distribution observed. If we assume standard model strength couplings of the W' boson to quark and lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c2 at 95% confidence level.     

Search for the standard model Higgs boson in the decay channel H→ZZ→4ℓ in pp collisions at √s=7 TeV

A search for a Higgs boson in the four-lepton decay channel H→ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range of 110100 GeV (with 13 below 160 GeV), while 67.1±6.0 (9.5±1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges of 134-158 GeV, 180-305 GeV, and 340-465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.     

Top-quark mass measurement from dilepton events at CDF II

We report a measurement of the top-quark mass using events collected by the CDF II detector from pp collisions at square root of s = 1.96 TeV at the Fermilab Tevatron. We calculate a likelihood function for the top-quark mass in events that are consistent with tt --> bl(-)nu(l)bl'+ nu'(l) decays. The likelihood is formed as the convolution of the leading-order matrix element and detector resolution functions. The joint likelihood is the product of likelihoods for each of 33 events collected in 340 pb(-1) of integrated luminosity, yielding a top-quark mass M(t) = 165.2 +/- 6.1(stat) +/- 3.4(syst) GeV/c2. This first application of a matrix-element technique to tt --> bl+ nu(l)bl'- nu(l') decays gives the most precise single measurement of M(t) in dilepton events. Combined with other CDF run II measurements using dilepton events, we measure M(t) = 167.9 +/- 5.2(stat) +/- 3.7(syst) GeV/c2.     

Measurement of the helicity of W bosons in top quark decays

We use the transverse momentum spectrum of leptons in the decay chain t-->bW with W-->lnu to measure the helicity of the W bosons in the top quark rest frame. Our measurement uses a t&tmacr; sample isolated in 106+/-4 pb(-1) of data collected in p&pmacr; collisions at sqrt[s] = 1.8 TeV with the CDF detector at the Fermilab Tevatron. Assuming a standard V-A weak decay, we find that the fraction of W's with zero helicity in the top rest frame is F0 = 0.91+/-0. 37(stat)+/-0.13(syst), consistent with the standard model prediction of F0 = 0.70 for a top mass of 175 GeV/c(2).     

Transverse momentum and total cross section of e(+)e(-) pairs in the Z-boson region from p&pmacr; collisions at sqrt

The transverse momentum and total cross section of e(+)e(-) pairs in the Z-boson region of 66相似文献   

Measurement of the tt production cross section in pp collisions at square root s = 1.96 TeV using missing E(T) + jets events with secondary vertex b tagging

We present a measurement of the tt production cross section in pp collisions at square root s = 1.96 TeV which uses events with an inclusive signature of significant missing transverse energy and jets. This is the first measurement which makes no explicit lepton identification requirements, so that sensitivity to W --> tau nu decays is maintained. Heavy flavor jets from top quark decay are identified with a secondary vertex tagging algorithm. From 311 pb(-1) of data collected by the Collider Detector at Fermilab, we measure a production cross section of 5.8 +/- 1.2(stat)(-0.7)(+0.9)(syst) pb for a top quark mass of 178 GeV/c2, in agreement with previous determinations and standard model predictions.     

Search for V+A current in top-quark decays in pp collisions at sqrts=1.96 TeV

We report an upper limit on the fraction of V+A current, fV+A, in top-quark decays, using approximately 700 pb-1 of pp[over ] collisions at sqrts=1.96 TeV acquired by the upgraded Collider Detector at Fermilab. For the decay t-->Wb-->lnub (where l=e or micro), the invariant mass of the charged lepton and the bottom quark jet is sensitive to the polarization of the W boson. We determine fV+A=-0.06+/-0.25 given a top-quark mass of 175 GeV/c2. We set an upper limit on fV+A of 0.29 at the 95% confidence level, an improvement by a factor of 2 on the previous best direct limit.     

Baryonic Z' explanation for the CDF Wjj excess

The latest CDF anomaly, the excess of dijet events in the invariant-mass window 120-160 GeV in associated production with a W boson, can be explained by a baryonic Z' model in which the Z' boson has negligible couplings to leptons. Although this Z' model is hardly subject to the Drell-Yan constraint from Tevatron, it is constrained by the dijet data from UA2 (√s=630 GeV), and the precision measurements at LEP through the mixing with the SM Z boson. We show that under these constraints this model can still explain the excess in the M(jj)～120-160 GeV window, as well as the claimed cross section σ(WZ')～4 pb. Implications at the Tevatron would be the associated production of γZ', ZZ', and Z'Z' with the Z'→jj. We show that with tightened jet cuts and improved systematic uncertainties both γZ'→γjj and ZZ'→?(+)?(-) jj channels could be useful to probe this model at the Tevatron.     

Search for excited and exotic electrons in the egamma decay channel in pp collisions at sqrt[s] = 1.96 TeV

We present a search for excited and exotic electrons (e(*)) decaying to an electron and a photon, both with high transverse momentum. We use 202 pb(-1) of data collected in pp collisions at sqrt[s] = 1.96 TeV with the Collider Detector at Fermilab II detector. No signal above standard model expectation is seen for associated ee(*) production. We discuss the e(*) sensitivity in the parameter space of the excited electron mass M(e(*)) and the compositeness energy scale Lambda. In the contact interaction model, we exclude 132 GeV/c(2)相似文献