165 research outputs found
Kpp and KKp Clusters
The three-body kaonic Kpp and KKp clusters are studied using the method of hyperspherical harmonics (HH) in momentum representation and differential Faddeev equations (DFE). We use different NN and KN interactions. Results obtained by the methods of HH and DFE are in reasonable agreement. The binding energy and the width show very strong dependence on the KN potential. We have two different classes of results: the results based on phenomenological strong KN potential, and the results obtained with much weaker chiral SU(3)-based KN potential
Cross Section Measurements of Charged Pion Photoproduction in Hydrogen and Deuterium from 1.1 to 5.5 GeV
The differential cross section for the gamma +n --> pi- + p and the gamma + p
--> pi+ n processes were measured at Jefferson Lab. The photon energies ranged
from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4
GeV. The pion center-of-mass angles varied from 50 degree to 110 degree. The
pi- and pi+ photoproduction data both exhibit a global scaling behavior at high
energies and high transverse momenta, consistent with the constituent counting
rule prediction and the existing pi+ data. The data suggest possible
substructure of the scaling behavior, which might be oscillations around the
scaling value. The data show an enhancement in the scaled cross section at
center-of-mass energy near 2.2 GeV. The differential cross section ratios at
high energies and high transverse momenta can be described by calculations
based on one-hard-gluon-exchange diagrams.Comment: 18 pages, 19 figure
Cross Section Measurement of Charged Pion Photoproduction from Hydrogen and Deuterium
We have measured the differential cross section for the gamma n --> pi- p and
gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon
energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon
energies greater than 3.3 GeV exhibit a global scaling behavior for both pi-
and pi+ photoproduction, consistent with the constituent counting rule and the
existing pi+ photoproduction data. Possible oscillations around the scaling
value are suggested by these new data The data show enhancement in the scaled
cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio
of exclusive pi- to pi+ photoproduction at high energy is consistent with the
prediction based on one-hard-gluon-exchange diagrams
Measurement of the Electric Form Factor of the Neutron at Q^2=0.5 and 1.0 (GeV/c)^2
The electric form factor of the neutron was determined from measurements of
the \vec{d}(\vec{e},e' n)p reaction for quasielastic kinematics. Polarized
electrons were scattered off a polarized deuterated ammonia target in which the
deuteron polarization was perpendicular to the momentum transfer. The scattered
electrons were detected in a magnetic spectrometer in coincidence with neutrons
in a large solid angle detector. We find G_E^n = 0.0526 +/- 0.0033 (stat) +/-
0.0026 (sys) and 0.0454 +/- 0.0054 +/- 0.0037 at Q^2 = 0.5 and 1.0 (GeV/c)^2,
respectively.Comment: 5 pages, 2 figures, as publishe
New Measurement of Parity Violation in Elastic Electron-Proton Scattering and Implications for Strange Form Factors
We have measured the parity-violating electroweak asymmetry in the elastic
scattering of polarized electrons from the proton. The result is A = -15.05 +-
0.98(stat) +- 0.56(syst) ppm at the kinematic point theta_lab = 12.3 degrees
and Q^2 = 0.477 (GeV/c)^2. The measurement implies that the value for the
strange form factor (G_E^s + 0.392 G_M^s) = 0.025 +- 0.020 +- 0.014, where the
first error is experimental and the second arises from the uncertainties in
electromagnetic form factors. This measurement is the first fixed-target parity
violation experiment that used either a `strained' GaAs photocathode to produce
highly polarized electrons or a Compton polarimeter to continuously monitor the
electron beam polarization.Comment: 8 pages, 4 figures, Tex, elsart.cls; revised version as accepted for
Phys. Lett.
Compton Scattering Cross Section on the Proton at High Momentum Transfer
Cross-section values for Compton scattering on the proton were measured at 25
kinematic settings over the range s = 5-11 and -t = 2-7 GeV2 with statistical
accuracy of a few percent. The scaling power for the s-dependence of the cross
section at fixed center of mass angle was found to be 8.0 +/ 0.2, strongly
inconsistent with the prediction of perturbative QCD. The observed
cross-section values are in fair agreement with the calculations using the
handbag mechanism, in which the external photons couple to a single quark.Comment: 5 pages, 5 figure
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