78 research outputs found
Evidence for the exclusive decay Bc+- to J/psi pi+- and measurement of the mass of the Bc meson
We report first evidence for a fully reconstructed decay mode of the
B_c^{\pm} meson in the channel B_c^{\pm} \to J/psi \pi^{\pm}, with J/psi \to
mu^+mu^-. The analysis is based on an integrated luminosity of 360 pb$^{-1} in
p\bar{p} collisions at 1.96 TeV center of mass energy collected by the Collider
Detector at Fermilab. We observe 14.6 \pm 4.6 signal events with a background
of 7.1 \pm 0.9 events, and a fit to the J/psi pi^{\pm} mass spectrum yields a
B_c^{\pm} mass of 6285.7 \pm 5.3(stat) \pm 1.2(syst) MeV/c^2. The probability
of a peak of this magnitude occurring by random fluctuation in the search
region is estimated as 0.012%.Comment: 7 pages, 3 figures. Version 3, accepted by PR
Top quark mass measurement using the template method at CDF
We present a measurement of the top quark mass in the lepton+jets and
dilepton channels of decays using the template method. The data
sample corresponds to an integrated luminosity of 5.6 fb of
collisions at Tevatron with TeV, collected with the CDF II
detector. The measurement is performed by constructing templates of three
kinematic variables in the lepton+jets and two kinematic variables in the
dilepton channel. The variables are two reconstructed top quark masses from
different jets-to-quarks combinations and the invariant mass of two jets from
the decay in the lepton+jets channel, and a reconstructed top quark mass
and , a variable related to the transverse mass in events with two
missing particles, in the dilepton channel. The simultaneous fit of the
templates from signal and background events in the lepton+jets and dilepton
channels to the data yields a measured top quark mass of Comment: submitted to Phys. Rev.
Measurement of the Dipion Mass Spectrum in X(3872) -> J/Psi Pi+ Pi- Decays
We measure the dipion mass spectrum in X(3872)--> J/Psi Pi+ Pi- decays using
360 pb-1 of pbar-p collisions at 1.96 TeV collected with the CDF II detector.
The spectrum is fit with predictions for odd C-parity (3S1, 1P1, and 3DJ)
charmonia decaying to J/Psi Pi+ Pi-, as well as even C-parity states in which
the pions are from Rho0 decay. The latter case also encompasses exotic
interpretations, such as a D0-D*0Bar molecule. Only the 3S1 and J/Psi Rho
hypotheses are compatible with our data. Since 3S1 is untenable on other
grounds, decay via J/Psi Rho is favored, which implies C=+1 for the X(3872).
Models for different J/Psi-Rho angular momenta L are considered. Flexibility in
the models, especially the introduction of Rho-Omega interference, enable good
descriptions of our data for both L=0 and 1.Comment: 7 pages, 4 figures -- Submitted to Phys. Rev. Let
Search for Higgs Boson Decaying to b-bbar and Produced in Association with W Bosons in p-pbar Collisions at sqrt{s}=1.96 TeV
We present a search for Higgs bosons decaying into b-bbar and produced in
association with W bosons in p-pbar collisions at sqrt{s}=1.96 TeV. This search
uses 320 pb-1 of the dataset 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, one of which is consistent with
a 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.Comment: 7 pages, 3 figures; updated title to published versio
Search for Second-Generation Scalar Leptoquarks in Collisions at =1.96 TeV
Results on a search for pair production of second generation scalar
leptoquark in collisions at =1.96 TeV are reported. The
data analyzed were collected by the CDF detector during the 2002-2003 Tevatron
Run II and correspond to an integrated luminosity of 198 pb. Leptoquarks
(LQ) are sought through their decay into (charged) leptons and quarks, with
final state signatures represented by two muons and jets and one muon, large
transverse missing energy and jets. We observe no evidence for production
and derive 95% C.L. upper limits on the production cross sections as well
as lower limits on their mass as a function of , where is the
branching fraction for .Comment: 9 pages (3 author list) 5 figure
Search for anomalous semileptonic decay of heavy flavor hadrons produced in association with a W boson at CDF II
We present a search for anomalous semileptonic decays of heavy flavor hadrons
produced in association with a boson, in proton-antiproton collisions at
sqrt{s}=1.96 TeV. We use 162 pb-1 of data collected with the CDF II detector at
the Fermilab Tevatron Collider. We select events with one W boson and at least
one jet with an identified secondary vertex. In the jets with a secondary
vertex we look for a semileptonic decay to a muon. We compare the number of
jets with both a secondary vertex and a semileptonic decay, and the kinematic
properties of these jets, with the standard model expectation of W plus heavy
flavor production and decay. No discrepancy is seen between the observation and
the expectation, and we set limits on the production cross section of a B-like
hadron with an anomalously high semileptonic branching ratio.Comment: 8 pages, 2 figures, submitted to PRD-RC; replaced to adjust the page
forma
Measurement of the Inclusive Jet Cross Section using the Kt algorithm in pp-bar Collisions at sqrt(s) = 1.96 TeV
We report on a measurement of the inclusive jet production cross section in
pp-bar collisions at sqrt{s} = 1.96 TeV using data collected with the upgraded
Collider Detector at Fermilab in Run II (CDF II) corresponding to an integrated
luminosity of 385 pb^-1. Jets are reconstructed using the kt algorithm. The
measurement is carried out for jets with rapidity 0.1 < | yjet | < 0.7 and
transverse momentum in the range 54 < ptjet < 700 GeV/c. The measured cross
section is in good agreement with next-to-leading order perturbative QCD
predictions after the necessary non-perturbative parton-to-hadron corrections
are included.Comment: Submitted to Phys. Rev. Let
Measurement of the Ratios of Branching Fractions B(Bs->Ds- pi+)/B(B0->D-pi+) and B(B+->D0bar pi+)/B(B0->D-pi+)
We report an observation of the decay Bs -> Ds- pi+ in p pbar collisions at
sqrt(s) = 1.96 TeV using 115 pb^(-1) of data collected by the CDF II detector
at the Fermilab Tevatron. We observe 83 +/- 11 Bs -> Ds- pi+ candidates,
representing a large increase in statistics over previous measurements and the
first observation of this decay at a p pbar collider. We present the first
measurement of the relative branching fraction B(Bs -> Ds- pi+) / B(B0 -> D-
pi+) = 1.32 +/- 0.18 (stat.) +/- 0.38 (syst.). We also measure B(B+ -> D0bar
pi+) / B(B0 -> D- pi+) = 1.97 +/- 0.10(stat.) +/- 0.21(syst.), which is
consistent with previous measurements
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 ppbar collisions at \sqrt{s} = 1.96 TeV at the Fermilab
Tevatron. We calculate a likelihood function for the top mass in events that
are consistent with ttbar->bbar l^- \nubar b l^+ \nu 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/c^2. This first
application of a matrix-element technique to ttbar->bbar l^- \nubar b l^+ \nu
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/c^2.Comment: 7 pages, 2 figures, To be published in Phys. Rev. Lett. Replacement
includes minor revisions made prior to acceptance by journa
Measurement of the Top Quark Mass with the Dynamical Likelihood Method using Lepton plus Jets Events with b-tags in ppbar Collisions at s**(1/2) = 1.96 TeV
This report describes a measurement of the top quark mass, M_{top}, with the
dynamical likelihood method (DLM) using the CDF II detector at the Fermilab
Tevatron. The Tevatron produces top/anti-top pairs in protons and anti-protons
collisions at a center-of-mass energy of 1.96 TeV. The data sample used in this
analysis was accumulated from March 2002 through August 2004, which corresponds
to an integrated luminosity of 318 pb^{-1}. We use the top/anti-top candidates
in the ``lepton+jets'' decay channel, requiring at least one jet identified as
a b quark by finding a displaced secondary vertex. The DLM defines a likelihood
for each event based on the differential cross section as a function of M_{top}
per unit phase space volume of the final partons, multiplied by the transfer
functions from jet to parton energies. The method takes into account all
possible jet combinations in an event, and the likelihood is multiplied event
by event to derive the top quark mass by the maximum likelihood method. Using
63 top quark candidates observed in the data, with 9.2 events expected from
background, we measure the top quark mass to be 173.2 +2.6/-2.4 (stat.) +/- 3.2
(syst.) GeV/c^2, or 173.2 +4.1/-4.0 GeV/c^2.Comment: 66 pages, 26 figures, 4 table
- …