The first search for single top quark production from the exchange of an $s$-channel virtual $W$ boson using events with an imbalance in the total transverse momentum, $b$-tagged jets, and no identified leptons is presented. The full data set collected by the Collider Detector at Fermilab, corresponding to an integrated luminosity of 9.45 fb$^{-1}$ from Fermilab Tevatron proton-antiproton collisions at a center of mass energy of 1.96 TeV, is used. Assuming the electroweak production of top quarks of mass 172.5 GeV/$c^2$ in the $s$-channel, a cross section of $1.12_{-0.57}^{+0.61}$ (stat+syst) pb, with a significance of 1.9 standard deviations, is measured. This measurement is combined with a previous result obtained from events with an imbalance in total transverse momentum, $b$-tagged jets, and exactly one identified lepton, yielding a cross section of $1.36_{-0.32}^{+0.37}$ (stat+syst) pb, with a significance of 4.2 standard deviations.
The s-channel single top quark cross section measured assuming top quarks of mass 172.5 GeV. The measurement uses a sample of events with large missing transverse energy, two or three jets of which one or more are b-tagged and no detected electron or muon candidates.
The combined s-channel single top quark cross section measurement assuming top quarks of mass 172.5 GeV. The measurement uses two samples of events. The first sample includes events with large missing transverse energy, two or three jets of which one or more are b-tagged and no detected electron or muon candidates. The second sample includes events with large missing transverse energy, one isolated muon or electron and two jets, at least one of which is b-tagged.
We present an analysis of top-antitop quark production and decay into a tau lepton, tau neutrino, and bottom quark using data from $9 {\rm fb}^{-1}$ of integrated luminosity at the Collider Detector at Fermilab. Dilepton events, where one lepton is an energetic electron or muon and the other a hadronically-decaying tau lepton, originating from proton-antiproton collisions at $\sqrt{s} = 1.96 TeV$ are used. A top-antitop quark production cross section of $8.1 \pm 2.1 {\rm pb}$ is measured, assuming standard-model top-quark decays. By separately identifying for the first time the single-tau and the ditau components, we measure the branching fraction of the top quark into tau lepton, tau neutrino, and bottom quark to be $(9.6 \pm 2.8) %$. The branching fraction of top-quark decays into a charged Higgs boson and a bottom quark, which would imply violation of lepton universality, is limited to be less than $5.9%$ at $95%$ confidence level.
The top-antitop quark production cross section measured assuming standard-model top-quark decays, TOP --> W BOTTOM.
The branching fraction of the top quark into a tau lepton, a tau neutrino and a bottom quark.
The ratio of leptonic top branching ratios, 2 * BR(TOP --> TAU NUTAU BOTTOM) / ( BR(TOP --> E NUE BOTTOM) + BR(TOP --> MU NUMU BOTTOM) ).
Drell-Yan lepton pairs are produced in the process $p\bar{p} \rightarrow \mu^+\mu^- + X$ through an intermediate $\gamma^*/Z$ boson. The forward-backward asymmetry in the polar-angle distribution of the $\mu^-$ as a function of the invariant mass of the $\mu^+\mu^-$ pair is used to obtain the effective leptonic determination $\sin^2 \theta^{lept}_{eff}$ of the electroweak-mixing parameter $\sin^2 \theta_W$, from which the value of $\sin^2 \theta_W$ is derived assuming the standard model. The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.2 fb-1 of integrated luminosity from $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of $\sin^2 \theta^{lept}_{eff}$ is found to be 0.2315 +- 0.0010, where statistical and systematic uncertainties are combined in quadrature. When interpreted within the context of the standard model using the on-shell renormalization scheme, where $\sin^2 \theta_W = 1 - M_W^2/M_Z^2$, the measurement yields $\sin^2 \theta_W$ = 0.2233 +- 0.0009, or equivalently a W-boson mass of 80.365 +- 0.047 GeV/c^2. The value of the W-boson mass is in agreement with previous determinations in electron-positron collisions and at the Tevatron collider.
The measured value of SIN**2(THETAEFF(LEPTON)).
The measured value of SIN**2(THETA(W)).
The measured value of M(W).
We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb-1 per experiment. The measured cross section is $\sigma_s = 1.29^{+0.26}_{-0.24}$ pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is $1.8 \times 10^{-10}$, corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks.
The measured cross section of single-top-quark production in the s channel.
We report evidence for $s$-channel single-top-quark production in proton-antiproton collisions at center-of-mass energy $\sqrt{s}= 1.96 \mathrm{TeV}$ using a data set that corresponds to an integrated luminosity of $9.4 \mathrm{fb}^{-1}$ collected by the Collider Detector at Fermilab. We select events consistent with the $s$-channel process including two jets and one leptonically decaying $W$ boson. The observed significance is $3.8$ standard deviations with respect to the background-only prediction. Assuming a top-quark mass of $172.5 \mathrm{GeV}/c^2$, we measure the $s$-channel cross section to be $1.41^{+0.44}_{-0.42} \mathrm{pb}$.
The s-channel cross section, measured assuming a top-quark mass of 172.5 GeV. The charge conjugate reaction is also included in the analysis.
We present a measurement of the ZZ boson-pair production cross section in 1.96 TeV center-of-mass energy ppbar collisions. We reconstruct final states incorporating four charged leptons or two charged leptons and two neutrinos from the full data set collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.7 fb-1 of integrated luminosity. Combining the results obtained from each final state, we measure a cross section of 1.04(+0.32)(-0.25) pb, in good agreement with the standard model prediction at next-to-leading order in the strong-interaction coupling.
The measured cross section for the process P PBAR --> Z0 Z0 --> LEPTON+ LEPTON- LEPTON+ LEPTON-.
The measured cross section for the process PBAR P --> Z0 Z0 --> LEPTON+ LEPTON- NU NUBAR.
The Z0 Z0 production cross section in PBAR P collisions obtained from the combination of the cross section measurements from the LEPTON+ LEPTON- LEPTON+ LEPTON- and LEPTON+ LEPTON- NU NUBAR signal samples.
Results are presented for the quasi two-body hypercharge exchange reactions of the type using data from a high statistics bubble chamber experiment. Total and differential cross sections and the momentum transfer dependence of the meson and hyperon resonance single density matrix elements are discussed. Amplitude analyses are performed for the first two reactions. The results are compared with quark model and duality predictions and with those from other related reactions.
No description provided.
No description provided.
No description provided.
We present a measurement of the elastic differential cross section $d\sigma(p\bar{p}\rightarrow p\bar{p})/dt$ as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of $\approx 31 nb^{-1}$ collected with the D0 detector using dedicated Tevatron $p\bar{p} $ Collider operating conditions at sqrt(s) = 1.96 TeV and covers the range $0.26 <|t|< 1.2 GeV^2$. For $|t|<0.6 GeV^2$, d\sigma/dt is described by an exponential function of the form $Ae^{-b|t|}$ with a slope parameter $ b = 16.86 \pm 0.10(stat) \pm 0.20(syst) GeV^{-2}$. A change in slope is observed at $|t| \approx 0.6 GeV^2$, followed by a more gradual |t| dependence with increasing values of |t|.
The $d\sigma$/$dt$ differential cross section. The statistical and systematic uncertainties are added in quadrature.
The total hadronic cross section for virtual photon-photon interactions is reported for center-of-mass energy, W, between 2 and 20 GeV. The data were obtained via the process e+e−→e+e−γ*γ*→e e−++hadrons with both scattered e+ and e− detected. Each photon’s four-momentum squared, q2, ranges from -0.1 to -1.6 GeV2. Dependence upon q2 agrees with a generalized vector-meson-dominance model. The total cross section shows little W dependence, averaging 125 nb at q12=q22=-0.3. Photon helicity interference terms are determined.
CROSS SECTION EXTRAPOLATED USING THE GENERALISED VECTOR CT. = Data are for >= 3 hadrons. DOMINANCE MODEL TO Q1=Q2=0.
Data are for >= 3 hadrons.
Data are for >= 3 hadrons.
Using data from the TPC/Two-Gamma experiment at the SLAC e+e− storage ring PEP, a C=+1 resonance has been observed in the π+π−π0γ final state resulting from the fusion of one nearly real and one quite virtual photon. The actual decay channel is probably π+π−π0π0, where one final-state photon is not detected, and the mass of the fully reconstructed state would be approximately 1525 MeV. A four-pion decay mode in turn implies that the resonance has even isospin. The nonobservation of this R(1525) when both initial-state photons are nearly real suggests a spin-1 assignment. Since the large measured value of the product of the branching ratio into π+π−π0π0 and the γγ coupling makes it unlikely that this state is the mostly s¯s f1(1510), its interpretation may lie outside of conventional meson spectroscopy. There is a second, less-significant enhancement observed in the same reaction at a four-pion mass centered around 2020 MeV.
No description provided.
Coupling parameter times the effective form factor.
Forum