187 research outputs found
Possibility of determinig the parity of the pentaquark from photoproduction near threshold
We discuss the possibility of determining the parity of the baryon
from photoproduction process near threshold. We utilize
the conservation laws of parity and angular momentum for the analysis of
angular distributions and spin observables near threshold. Since the discussion
is in essence a partial wave analysis of the production mechanism the result
should be less dependent on the model parameters. Our analysis shows that the
angular distribution and photon polarization asymmetry for the process of
neutron target are sensitive to the parity of the , but not for the
case of proton target. In the case of proton target, the polarization
asymmetries of target and recoiled are preferred for parity
determination.Comment: 23 pages, 13 figures, extended versio
Observation and Mass Measurement of the Baryon
We report the observation and measurement of the mass of the bottom, strange
baryon through the decay chain , where
, , and .
Evidence for observation is based on a signal whose probability of arising from
the estimated background is 6.6 x 10^{-15}, or 7.7 Gaussian standard
deviations. The mass is measured to be (stat.) (syst.) MeV/.Comment: Minor text changes for the second version. Accepted by Phys. Rev.
Let
Measurement of the Cross Section and Triple Gauge Couplings in Collisions at TeV
This Letter describes the current most precise measurement of the
production cross section as well as limits on anomalous couplings at a
center-of-mass energy of 1.96 TeV in proton-antiproton collisions for the
Collider Detector at Fermilab (CDF). candidates are reconstructed from
decays containing three charged leptons and missing energy from a neutrino,
where the charged leptons are either electrons or muons. Using data collected
by the CDF II detector (7.1 fb of integrated luminosity), 63 candidate
events are observed with the expected background contributing events.
The measured total cross section pb is in good
agreement with the standard model prediction of . The same sample
is used to set limits on anomalous couplings.Comment: Resubmission to PRD-RC after acceptance (27 July 2012
Measurement of the Lifetime Difference Between B_s Mass Eigenstates
We present measurements of the lifetimes and polarization amplitudes for B_s
--> J/psi phi and B_d --> J/psi K*0 decays. Lifetimes of the heavy (H) and
light (L) mass eigenstates in the B_s system are separately measured for the
first time by determining the relative contributions of amplitudes with
definite CP as a function of the decay time. Using 203 +/- 15 B_s decays, we
obtain tau_L = (1.05 +{0.16}/-{0.13} +/- 0.02) ps and tau_H = (2.07
+{0.58}/-{0.46} +/- 0.03) ps. Expressed in terms of the difference DeltaGamma_s
and average Gamma_s, of the decay rates of the two eigenstates, the results are
DeltaGamma_s/Gamma_s = (65 +{25}/-{33} +/- 1)%, and DeltaGamma_s = (0.47
+{0.19}/-{0.24} +/- 0.01) inverse ps.Comment: 8 pages, 3 figures, 2 tables; as published in Physical Review Letters
on 16 March 2005; revisions are for length and typesetting only, no changes
in results or conclusion
Polarizations of J/psi and psi(2S) Mesons Produced in ppbar Collisions at 1.96 TeV
We have measured the polarizations of \jpsi and \psiprime mesons as
functions of their transverse momentum \pt when they are produced promptly in
the rapidity range with \pt \geq 5 \pgev. The analysis is performed
using a data sample with an integrated luminosity of about 800 \ipb collected
by the CDF II detector. For both vector mesons, we find that the polarizations
become increasingly longitudinal as \pt increases from 5 to 30 \pgev. These
results are compared to the predictions of nonrelativistic quantum
chromodynamics and other contemporary models. The effective polarizations of
\jpsi and \psiprime mesons from -hadron decays are also reported.Comment: 8 pages, 7 figures, published in Physical Review Letter
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 (). The top quark mass is extracted
using a direct calculation of the probability density that each event
corresponds to the 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 {\it in situ} by the hadronic boson mass. Using 167 events
observed in 955 pb of integrated luminosity, we achieve the single
most precise measurement of the top quark mass, 170.8 2.2 (stat.)
1.4 (syst.) GeV/.Comment: accepted by Phys. Rev. Let
Measurement of B(t->Wb)/B(t->Wq) at the Collider Detector at Fermilab
We present a measurement of the ratio of top-quark branching fractions R= B(t
-> Wb)/B(t -> Wq), where q can be a b, s or a d quark, using lepton-plus-jets
and dilepton data sets with integrated luminosity of ~162 pb^{-1} collected
with the Collider Detector at Fermilab during Run II of the Tevatron. The
measurement is derived from the relative numbers of t-tbar events with
different multiplicity of identified secondary vertices. We set a lower limit
of R > 0.61 at 95% confidence level.Comment: 7 pages, 2 figures, published in Physical Review Letters; changes
made to be consistent with published versio
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
Search for Third Generation Vector Leptoquarks in p anti-p Collisions at sqrt(s) = 1.96 TeV
We describe a search for a third generation vector leptoquark (VLQ3) that
decays to a b quark and tau lepton using the CDF II detector and 322 pb^(-1) of
integrated luminosity from the Fermilab Tevatron. Vector leptoquarks have been
proposed in many extensions of the standard model (SM). Observing a number of
events in agreement with SM expectations, assuming Yang-Mills (minimal)
couplings, we obtain the most stringent upper limit on the VLQ3 pair production
cross section of 344 fb (493 fb) and lower limit on the VLQ3 mass of 317
GeV/c^2 (251 GeV/c^2) at 95% C.L.Comment: 7 pages, 2 figures, submitted to PR
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