263 research outputs found
Faddeev study of heavy baryon spectroscopy
We investigate the structure of heavy baryons containing a charm or a bottom
quark. We employ a constituent quark model successful in the description of the
baryon-baryon interaction which is consistent with the light baryon spectra. We
solve exactly the three-quark problem by means of the Faddeev method in
momentum space. Heavy baryon spectrum shows a manifest compromise between
perturbative and nonperturbative contributions. The flavor dependence of the
one-gluon exchange is analyzed. We assign quantum numbers to some already
observed resonances and we predict the first radial and orbital excitations of
all states with or 3/2. We combine our results with heavy quark
symmetry and lowest-order SU(3) symmetry breaking to predict the masses and
quantum numbers of six still non-measured ground-state beauty baryons.Comment: 22 pages, 4 figures, 8 tables. Accepted for publication in J. Phys.
Heavy Quark Spectroscopy -- Theory Overview
Some recent discoveries in the spectroscopy of hadrons containing heavy
quarks, and some of their theoretical interpretations, are reviewed.Comment: 13 pages, 6 figures. Presented at Second Meeting of APS Topical Group
on Hadron Physics, Nashville, TN, 22-24. Proceedings to be published by
Journal of Physics (UK), Conference Series. Uses jpconf.cls, jpconf11.clo.
Some corrections; references update
Pentaquarks: review of the experimental evidence
Pentaquarks, namely baryons made by 4 quarks and one antiquark have been
predicted and searched for since several decades without success. Theoretical
and experimental advances in the last 2 years led to the observation of a
number of pentaquark candidates. We review the experimental evidence for
pentaquarks as well as their non-observations by some experiments, and discuss
to which extend these sometimes contradicting informations may lead to a
consistent picture.Comment: Contribution to the International Conference on 'Strangeness in Quark
Matter', 15-21 Sept. 2004, Cape Tawn, South Afric
Hadron Spectroscopy: Theory and Experiment
Many new results on hadron spectra have been appearing in the past few years
thanks to improved experimental techniques and searches in new channels. New
theoretical techniques including refined methods of lattice QCD have kept pace
with these developments. Much has been learned about states made of both light
(u, d, and s) and heavy (c, b) quarks. The present review treats light-quark
mesons, glueballs, hybrids, particles with a single c or b quark, charmonium,
and bottomonium states. Some prospects for further study are noted.Comment: 29 pages, 9 figures, to be published in Journal of Physics G. Further
updating of reference
Limits on Anomalous Triple Gauge Couplings in ppbar Collisions at sqrt{s}=1.96 TeV
We present a search for anomalous triple gauge couplings (ATGC) in WW and WZ
boson production. The boson pairs are produced in ppbar collisions at
sqrt{s}=1.96 TeV, and the data sample corresponds to 350 pb-1 of integrated
luminosity collected with the CDF II detector at the Fermilab Tevatron. In this
search one W decays to leptons, and the other boson (W or Z) decays
hadronically. Combining with a previously published CDF measurement of Wgamma
boson production yields ATGC limits of -0.18 < lambda < 0.17 and -0.46 < Delta
kappa < 0.39 at the 95% confidence level, using a cut-off scale Lambda=1.5 TeV.Comment: 7 pages, 3 figures. Submitted to Phys. Rev.
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
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
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
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
Measurement of the Lambda_b Lifetime in Lambda_b --> J/psi Lambda0 in p-pbar Collisions at sqrt(s)=1.96 TeV
We report a measurement of the Lambda_b lifetime in the exclusive decay
Lambda_b --> J/psi Lambda0 in p-pbar collisions at sqrt(s) = 1.96 TeV using an
integrated luminosity of 1.0 fb^{-1} of data collected by the CDF II detector
at the Fermilab Tevatron. Using fully reconstructed decays, we measure
tau(Lambda_b) = 1.593 ^{+0.083}_{-0.078} (stat.) +- 0.033 (syst.) ps. This is
the single most precise measurement of tau(Lambda_b) and is 3.2 sigma higher
than the current world average.Comment: 7 Pages, 2 Figures, 1 Table. Submitted to Phys. Rev. Let
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