46 research outputs found
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s) = 1.96 TeV
We present a measurement of the top quark pair production cross section in
ppbar collisions at sqrt(s)=1.96 TeV using 318 pb^{-1} of data collected with
the Collider Detector at Fermilab. We select ttbar decays into the final states
e nu + jets and mu nu + jets, in which at least one b quark from the t-quark
decays is identified using a secondary vertex-finding algorithm. Assuming a top
quark mass of 178 GeV/c^2, we measure a cross section of 8.7 +-0.9 (stat)
+1.1-0.9 (syst) pb. We also report the first observation of ttbar with
significance greater than 5 sigma in the subsample in which both b quarks are
identified, corresponding to a cross section of 10.1 +1.6-1.4(stat)+2.0-1.3
(syst) pb.Comment: Accepted for publication in Physics Review Letters, 7 page
Search for New Physics in Lepton + Photon + X Events with L=305 pb-1 of ppbar Collisions at roots=1.96 TeV
We present results of a search for anomalous production of events containing
a charged lepton (either electron or muon) and a photon, both with high
transverse momentum, accompanied by additional signatures, X, including missing
transverse energy (MET) and additional leptons and photons. We use the same
kinematic selection criteria as in a previous CDF search, but with a
substantially larger data set, 305 pb-1, a ppbar collision energy of 1.96 TeV,
and the upgraded CDF II detector. We find 42 Lepton+Photon+MET events versus a
standard model expectation of 37.3 +- 5.4 events. The level of excess observed
in Run I, 16 events with an expectation of 7.6 +- 0.7 events (corresponding to
a 2.7 sigma effect), is not supported by the new data. In the signature of
Multi-Lepton+Photon+X we observe 31 events versus an expectation of 23.0 +- 2.7
events. In this sample we find no events with an extra photon or MET and so
find no events like the one ee+gg+MET event observed in Run I.Comment: 7 pages, 3 figures, 1 table. Accepted to PR
Top Quark Mass Measurement from Dilepton Events at CDF II with the Matrix-Element Method
We describe a measurement of the top quark mass using events with two charged
leptons collected by the CDF II detector from collisions with TeV at the Fermilab Tevatron. The likelihood in top mass is
calculated for each event by convoluting the leading order matrix element
describing
with detector resolution functions. The presence of background events in the
data sample is modeled using similar calculations involving the matrix elements
for major background processes. In a data sample with integrated luminosity of
340 pb, we observe 33 candidate events and measure This
measurement represents the first application of this method to events with two
charged leptons and is the most precise single measurement of the top quark
mass in this channel.Comment: 21 pages, 14 figure
Measurement of the Ratio of Branching Fractions B(D0 -> K+ pi-)/B(D0 -> K- pi+) using the CDF II Detector
We present a measurement of R_B, the ratio of the branching fraction for the
rare decay D0 -> K+ pi- to that for the Cabibbo-favored decay D0 -> K- pi+.
Charge conjugate decays are implicitly included. A signal of 2005 +/- 104
events for the decay D0 -> K+ pi- is obtained using the CDF II detector at the
Fermilab Tevatron collider. The data set corresponds to an integrated
luminosity of 0.35 1/fb produced in p-bar/p collisions at sqrt{s}=1.96 TeV.
Assuming no mixing, we find R_B = [ 4.05 +/- 0.21 (stat) +/- 0.11 (syst) ] x
10(-3). This measurement is consistent with the world average, and comparable
in accuracy with the best measurements from other experiments.Comment: 7 pages, 3 figure
Measurement of the ttbar Production Cross Section in ppbar collisions at sqrt{s} = 1.96 TeV using Lepton+Jets Events with Jet Probability b-tagging
We present a measurement of the ttbar production cross section using events
with one charged lepton and jets from ppbar collisions at a center-of-mass
energy of 1.96 TeV. A b-tagging algorithm based on the probability of displaced
tracks coming from the event interaction vertex is applied to identify b quarks
from top decay. Using 318 pb^{-1} of data collected with the CDF II detector,
we measure the ttbar production cross section in events with at least one
restrictive (tight) b-tagged jet and obtain 8.9 +1.0-1.0 (stat.) +1.1-1.0
(syst.) pb. The cross section value assumes a top quark mass of m_{t}=178 GeV
in the acceptance corrections. The dependence of the cross section on m_t is
presented in the paper. This result is consistent with other CDF measurements
of the ttbar cross section using different samples and analysis techniques, and
has similar systematic uncertainties. We have also performed consistency checks
by using the b-tagging probability function to vary the signal to background
ratio and also using events that have at least two b-tagged jets.Comment: 45 pages, 27 figures, submitted to Physical Review
Search for large extra dimensions in the production of jets and missing transverse energy in p(p)over-bar collisions at root s=1.96 TeV
We present the results of a search for new physics in the jets plus missing transverse energy data sample collected from 368 pb(-1) of p (p) over bar collisions at root s = 1.96 TeV recorded by the Collider Detector at Fermilab. We compare the number of events observed in the data with a data-based estimate of the standard model backgrounds contributing to this signature. We observe no significant excess of events, and we interpret this null result in terms of lower limits on the fundamental Planck scale for a large extra dimensions scenario
Measurement of the Top Quark Mass using Template Methods on Dilepton Events in Proton-Antiproton Collisions at sqrt(s)=1.96 TeV
We describe a measurement of the top quark mass from events produced in
proton-antiproton collisions at a center-of-mass energy of 1.96 TeV, using the
Collider Detector at Fermilab. We identify top-antitop candidates where both W
bosons from the top quarks decay into leptons (electron, muon, or tau plus
neutrino) from a data sample of 360 inverse picobarns. The top quark mass is
reconstructed in each event separately by three different methods, which draw
upon simulated distributions of the neutrino pseudorapidity, top-antitop
longitudinal momentum, or neutrino azimuthal angle in order to extract
probability distributions for the top quark mass. For each method,
representative mass distributions, or templates, are constructed from simulated
samples of signal and background events, and parameterized to form continuous
probability density functions. A likelihood fit incorporating these
parameterized templates is then performed on the data sample masses in order to
derive a final top quark mass. Combining the three template methods, taking
into account correlations in their statistical and systematic uncertainties,
results in a top quark mass measurement of 170.1 +/- 6.0 (stat) +/- 4.1 (syst)
GeV/c^2.Comment: 52 pages, 23 figures, 5 tables. Submitted to Physical Review
Observation of Bs to Psi(2S)phi and Measurement of Ratio of Branching Fractions B (Bs --> Psi(2S)phi) / B (Bs --> J/Psi phi)
We report the first observation of Bs to Psi(2S) phi signals using 360 pb^-1
of CDF Run II data sample, where Psi(2S) decays into mu+mu- and J/psi pi+pi-
modes with phi decays to K+K-. We have measured the relative branching ratio of
Br(Bs to Psi(2S)phi)/Br(Bs to J/psi phi) using J/psi, Psi(2S) to mu+mu- decay
mode. We obtain Br(Bs to Psi(2S)phi)/Br(Bs to J/psi phi) = 0.52 +- 0.13 (stat.)
+- 0.04 (syst.) +- 0.06 (BR).Comment: 14 pages, 4 figures, submitted to Phys.Rev.Let
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Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions at root s=1.96 TeV
The production cross-sections of mesons in proton-proton collisions
at a centre-of-mass energy of TeV are measured using a data sample
corresponding to an integrated luminosity of ,
collected by the LHCb experiment. The cross-sections are measured
differentially as a function of transverse momentum, , and
rapidity, , and separately for mesons produced promptly and from
beauty hadron decays (nonprompt). With the assumption of unpolarised
mesons, the production cross-sections integrated over the kinematic range
and are
for prompt mesons and
for nonprompt mesons, where the
first uncertainties are statistical and the second systematic. These
cross-sections are compared with those at TeV and TeV, and
are used to update the measurement of the nuclear modification factor in
proton-lead collisions for mesons at a centre-of-mass energy per
nucleon pair of TeV. The results are compared with
theoretical predictions
Measurement of the ratio of branching fractions B(D-0 -\u3e K+pi(-))/B(D-0 -\u3e K-pi(+)) using the CDF II detector
We present a measurement of RB, the ratio of the branching fraction for the rare decay D-0 -\u3e K+pi(-) to that for the Cabibbo-favored decay D-0 -\u3e K-pi(+). Charge-conjugate decays are implicitly included. A signal of 2005 +/- 104 events for the decay D-0 -\u3e K+pi(-) is obtained using the CDF II detector at the Fermilab Tevatron collider. The data set corresponds to an integrated luminosity of 0.35 fb(-1) produced in (p) over barp collisions at root s\u3e=1.96 TeV. Assuming no mixing, we find R-E=[4.05 +/- 0.21(stat)+/- 0.11(syst)]x10(-3). This measurement is consistent with the world average, and comparable in accuracy with the best measurements from other experiments