244 research outputs found
Deuteron Electroweak Disintegration
We study the deuteron electrodisintegration with inclusion of the neutral
currents focusing on the helicity asymmetry of the exclusive cross section in
coplanar geometry. We stress that a measurement of this asymmetry in the quasi
elastic region is of interest for an experimental determination of the weak
form factors of the nucleon, allowing one to obtain the parity violating
electron neutron asymmetry. Numerically, we consider the reaction at low
momentum transfer and discuss the sensitivity of the helicity asymmetry to the
strangeness radius and magnetic moment. The problems coming from the finite
angular acceptance of the spectrometers are also considered.Comment: 30 pages, Latex, 7 eps figures, submitted to Phys.Rev.C e-mail:
[email protected] , [email protected]
Vertex functions for d-wave mesons in the light-front approach
While the light-front quark model (LFQM) is employed to calculate hadronic
transition matrix elements, the vertex functions must be pre-determined. In
this work we derive the vertex functions for all d-wave states in this model.
Especially, since both of and are mesons, the Lorentz
structures of their vertex functions are the same. Thus when one needs to study
the processes where is involved, all the corresponding formulas for
states can be directly applied, only the coefficient of the vertex
function should be replaced by that for . The results would be useful
for studying the newly observed resonances which are supposed to be d-wave
mesons and furthermore the possible 2S-1D mixing in with the LFQM.Comment: 12 pages, 2 figures, some typos corrected and more discussions added.
Accepted by EPJ
Parity violating target asymmetry in electron - proton scattering
We analyze the parity-violating (PV) components of the analyzing power in
elastic electron-proton scattering and discuss their sensitivity to the strange
quark contributions to the proton weak form factors. We point out that the
component of the analyzing power along the momentum transfer is independent of
the electric weak form factor and thus compares favorably with the PV beam
asymmetry for a determination of the strangeness magnetic moment. We also show
that the transverse component could be used for constraining the strangeness
radius. Finally, we argue that a measurement of both components could give
experimental information on the strangeness axial charge.Comment: 24 pages, Latex, 5 eps figures, submitted to Phys.Rev.
A Measurement of Psi(2S) Resonance Parameters
Cross sections for e+e- to hadons, pi+pi- J/Psi, and mu+mu- have been
measured in the vicinity of the Psi(2S) resonance using the BESII detector
operated at the BEPC. The Psi(2S) total width; partial widths to hadrons,
pi+pi- J/Psi, muons; and corresponding branching fractions have been determined
to be Gamma(total)= (264+-27) keV; Gamma(hadron)= (258+-26) keV, Gamma(mu)=
(2.44+-0.21) keV, and Gamma(pi+pi- J/Psi)= (85+-8.7) keV; and Br(hadron)=
(97.79+-0.15)%, Br(pi+pi- J/Psi)= (32+-1.4)%, Br(mu)= (0.93+-0.08)%,
respectively.Comment: 8 pages, 6 figure
Measurements of the Mass and Full-Width of the Meson
In a sample of 58 million events collected with the BES II detector,
the process J/ is observed in five different decay
channels: , , (with ), (with
) and . From a combined fit of all five
channels, we determine the mass and full-width of to be
MeV/ and
MeV/.Comment: 9 pages, 2 figures and 4 table. Submitted to Phys. Lett.
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
Measurement of Transverse Single-Spin Asymmetries for Di-Jet Production in Proton-Proton Collisions at GeV
We report the first measurement of the opening angle distribution between
pairs of jets produced in high-energy collisions of transversely polarized
protons. The measurement probes (Sivers) correlations between the transverse
spin orientation of a proton and the transverse momentum directions of its
partons. With both beams polarized, the wide pseudorapidity () coverage for jets permits separation of Sivers functions for the valence
and sea regions. The resulting asymmetries are all consistent with zero and
considerably smaller than Sivers effects observed in semi-inclusive deep
inelastic scattering (SIDIS). We discuss theoretical attempts to reconcile the
new results with the sizable transverse spin effects seen in SIDIS and forward
hadron production in pp collisions.Comment: 6 pages total, 1 Latex file, 3 PS files with figure
Isozyme and RAPD studies in Prosopis glandulosa and P. Velutina (Leguminosae, Mimosoideae)
Evidence of psi(3770) non-DD-bar Decay to J/psi pi+pi-
Evidence of decays to a non- final state is
observed. A total of \psi(3770) \to \PPJP events are
obtained from a data sample of 27.7 taken at center-of-mass
energies around 3.773 GeV using the BES-II detector at the BEPC. The branching
fraction is determined to be BF(\psi(3770) \to \PPJP)=(0.34\pm 0.14 \pm
0.09)%, corresponding to the partial width of \Gamma(\psi(3770) \to \PPJP) =
(80 \pm 33 \pm 23) keV.Comment: 8 pages, 7 figures, Submitted to Physics Letters
Potassium permanganate effects in postharvest conservation of the papaya cultivar Sunrise Golden
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