51 research outputs found
Evidence for a J/psi-ppbar Pauli Strong Coupling ?
The couplings of charmonia and charmonium hybrids (generically Psi) to ppbar
are of great interest in view of future plans to study these states using an
antiproton storage ring at GSI. These low to moderate energy Psi-ppbar
couplings are not well understood theoretically, and currently must be
determined from experiment. In this letter we note that the two independent
Dirac (gamma_mu) and Pauli (sigma_munu) ppbar couplings of the J/psi and psi'
can be constrained by the angular distribution of e+e- -> (J/psi, psi') ->
ppbar on resonance. A comparison of our theoretical results to recent
unpolarized data allows estimates of the ppbar couplings; in the better
determined J/psi case the data is inconsistent with a pure Dirac (gamma_mu)
coupling, and can be explained by the presence of a sigma_munu term. This Pauli
coupling may significantly affect the cross section of the PANDA process p pbar
-> pi0 J/psi near threshold. There is a phase ambiguity that makes it
impossible to uniquely determine the magnitudes and relative phase of the Dirac
and Pauli couplings from the unpolarized angular distributions alone; we show
in detail how this can be resolved through a study of the polarized reactions.Comment: 7 pages, 7 figures. v2 generalizes v1 to complex J/psi-ppbar
coupling
On the Particle Data Group evaluation of Psi' and chi_c Branching Ratios
I propose a new evaluation of and branching ratios
which avoids the correlations affecting the current Particle Data Group
evaluation.
These correlations explain the apparent technique-dependent discrepancies
between the available determinations of the
and under the hypotesis that the current
values of the branching ratios are
overestimated.
In the process I also noticed that Particle Data Group has not restated many
of the older measurements, when necessary, for the new value of , which significantly affects the evaluation of some
relevant and exclusive branching ratios.Comment: 13 pages. Revised version. Submitted to Phys. Rev.
E835 at FNAL: Charmonium Spectroscopy in Annihilations
I present preliminary results on the search for in its
and decay modes. We observe an excess of \eta_c\gamma{\cal P} \sim 0.001M=3525.8 \pm 0.2 \pm 0.2
\Gamma\leq10.6\pm 3.7\pm3.4(br) <
\Gamma_{\bar{p}p}B_{\eta_c\gamma} < 12.8\pm 4.8\pm4.5(br) J/\psi\pi^0$ mode.Comment: Presented at the 6th International Conference on Hyperons, Charm and
Beauty Hadrons (BEACH 2004), Chicago(Il), June 27-July 3,200
Charmless Three-Body Baryonic B Decays
Motivated by recent data on B-> p pbar K decay, we study various charmless
three-body baryonic B decay modes, including Lambda pbar pi, Sigma0 pbar pi, p
pbar pi, p pbar Kbar0, in a factorization approach. These modes have rates of
order 10^{-6}. There are two mechanisms for the baryon pair production,
current-produced and transition. The behavior of decay spectra from these
baryon production mechanisms can be understood by using QCD counting rules.
Predictions on rates and decay spectra can be checked in the near future.Comment: 26 pages, 9 figures; version to appear in Phys. Rev.
Closed-flavor pi + J/psi and pi + Upsilon Cross Sections at Low Energies from Dipion Decays
The scale of low energy c-cbar and b-bbar cross sections on light hadrons is
of great importance to searches for the quark gluon plasma using the
heavy-quarkonium suppression signature. Unfortunately, little is known about
these near-threshold cross sections at present, and recent theoretical
estimates span many orders of magnitude. Here we use experimental data on the
four observed closed-flavor heavy quarkonium hadronic decays psi' -> pi pi
J/psi, Upsilon' -> pi pi Upsilon, Upsilon'' -> pi pi Upsilon and Upsilon'' ->
pi pi Upsilon', combined with simple models of the transition amplitudes, to
estimate the pion scattering cross sections of c-cbar and b-bbar mesons near
threshold. Specifically we consider the closed-flavor reactions pi J/psi -> pi
psi', pi Upsilon -> pi Upsilon', pi Upsilon -> pi Upsilon'' and pi Upsilon' ->
pi Upsilon'' and their time-reversed analogues. Our results may be useful in
constraining theoretical models of the strong interactions of heavy quarkonia,
and can be systematically improved through future detailed studies of dipion
decays, notably psi' -> pi pi J/psi and Upsilon'' -> pi pi Upsilon.Comment: 6 pages, 6 figure
Recalculation of Proton Compton Scattering in Perturbative QCD
At very high energy and wide angles, Compton scattering on the proton (gamma
p -> gamma p) is described by perturbative QCD. The perturbative QCD
calculation has been performed several times previously, at leading twist and
at leading order in alpha_s, with mutually inconsistent results, even when the
same light-cone distribution amplitudes have been employed. We have
recalculated the helicity amplitudes for this process, using contour
deformations to evaluate the singular integrals over the light-cone momentum
fractions. We do not obtain complete agreement with any previous result. Our
results are closest to those of the most recent previous computation, differing
significantly for just one of the three independent helicity amplitudes, and
only for backward scattering angles. We present results for the unpolarized
cross section, and for three different polarization asymmetries. We compare the
perturbative QCD predictions for these observables with those of the handbag
and diquark models. In order to reduce uncertainties associated with alpha_s
and the three-quark wave function normalization, we have normalized the Compton
cross section using the proton elastic form factor. The theoretical predictions
for this ratio are about an order of magnitude below existing experimental
data.Comment: Latex, 23 pages, 13 figures. Checked numerical integration one more
way; added results for one more proton distribution amplitude; a few other
minor changes. Version to appear in Phys. Rev.
Tracking Performance of the Scintillating Fiber Detector in the K2K Experiment
The K2K long-baseline neutrino oscillation experiment uses a Scintillating
Fiber Detector (SciFi) to reconstruct charged particles produced in neutrino
interactions in the near detector. We describe the track reconstruction
algorithm and the performance of the SciFi after three years of operation.Comment: 24pages,18 figures, and 1 table. Preprint submitted to NI
Branching Fraction Measurements of psi(2S) Decay to Baryon-Antibaryon Final States
Using 3.08 million psi(2S) decays observed in e^+e^- collisions by the CLEO
detector, we present the results of a study of the psi(2S) decaying into
baryon-antibaryon final states. We report the most precise measurements of the
following eight modes: proton-antiproton, lambda-antilambda, Xi^- antiXi^-,
Xi^0-antiXi^0 (first observation), Sigma+-antiSigma^+ (first observation), and
Sigma^0-antiSigma^0, and place upper limits for the modes, Xi^0*-antiXi^0* and
Omega^- antiOmega^-.Comment: 8 pages postscript,also available through
http://www.lns.cornell.edu/public/CLNS/2005/, submitted to PR
Measurement of the Resonance Parameters of the and States of Charmonium formed in Antiproton-Proton Annihilations
We have studied the ( states of charmonium in formation by
antiproton-proton annihilations in experiment E835 at the Fermilab Antiproton
Source. We report new measurements of the mass, width, and for the
and by means of the inclusive reaction . Using the subsample of
events where is
fully reconstructed, we derive . We summarize the results of the E760
(updated) and E835 measurements of mass, width and (J=0,1,2) and discuss the significance of
these measurements
Measurements of psi(2S) decays to octet baryon-antibaryon pairs
With a sample of 14 million psi(2S) events collected by the BESII detector at
the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p
p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their
branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4,
(3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4,
respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter
alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure
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