582 research outputs found
Analyzing Powers and Spin Correlation Coefficients for p+d Elastic Scattering at 135 and 200 MeV
The proton and deuteron analyzing powers and 10 of the possible 12 spin
correlation coefficients have been measured for p+d elastic scattering at
proton bombarding energies of 135 and 200 MeV. The results are compared with
Faddeev calculations using two different NN potentials. The qualitative
features of the extensive data set on the spin dependence in p+d elastic
scattering over a wide range of angles presented here are remarkably well
explained by two-nucleon force predictions without inclusion of a three-nucleon
force. The remaining discrepancies are, in general, not alleviated when
theoretical three-nucleon forces are included in the calculations.Comment: 43 pages, 12 figures, accepted for publication by Phys. Rev.
Parity violation in deuteron photo-disintegration
We analyze the energy dependence for two types of parity-non-conserving
(PNC) asymmetries in the reaction in the near-threshold
region. The first one is the asymmetry in reaction with circularly polarized
photon beam and unpolarized deuteron target. The second one corresponds to
those with an unpolarized photon beam and polarized target. We find that the
two asymmetries have quite different energy dependence, and their shapes are
sensitive to the PNC-meson exchange coupling constants.
The predictions for the future possible experiments to provide definite
constraints for the PNC-coupling constants are discussed.Comment: 22 pages, 12 figures. Submitted to Phys.Rev.C 10Oct.0
Host Factors Selectively Increase Staphylococcal Adherence on Inserted Catheters: A Role for Fibronectin and Fibrinogen or Fibrin
Intravascular catheters are prone to staphylococcal infections. To study the role in staphylococcal adherence played by fibrinogen or fibrin and fibronectin deposited on inserted catheters, 187 peripheral or central cannulae were prospectively removed from hospitalized patients. Compared with uninserted catheters, which allowed only minimal adherence, previously inserted catheters promoted significant adherence of staphylococcal isolates from patients with intravenous device infections. Adhesion-promoting properties were studied with laboratory strains having well-defined affinities for either fibronectin or fibrinogen adherence of Staphylococcus aureus Cowan I, which has the highest affinity for both adhesins, was more strongly promoted (10- to 50-fold) on inserted cannulae than was that of S. aureus Wood 46 (4- to lO-fold) or Staphylococcus epidermidis Rp 12 (2.2-fold), which has no affinity for fibrinogen but does for fibronectin. Although all types of cannulae contained significant amounts of fibrin, which may promote adherence of coagulase-positive staphylococci, results obtained with coagulase-negative isolates suggested that in vivo-deposited fibronectin is also a critical determinant in this proces
Dependence of pp->pp pi0 near Threshold on the Spin of the Colliding Nucleons
A polarized internal atomic hydrogen target and a stored, polarized beam are
used to measure the spin-dependent total cross section Delta_sigma_T/sigma_tot,
as well as the polar integrals of the spin correlation coefficient combination
A_xx-A_yy, and the analyzing power A_y for pp-> pp pi0 at four bombarding
energies between 325 and 400 MeV. This experiment is made possible by the use
of a cooled beam in a storage ring. The polarization observables are used to
study the contribution from individual partial waves.Comment: 6 pages, 1 table, 4 figures, corrected equations 2 and
Parity Violation in gamma proton Compton Scattering
A measurement of parity-violating spin-dependent gamma proton Compton
scattering will provide a theoretically clean determination of the
parity-violating pion-nucleon coupling constant . We
calculate the leading parity-violating amplitude arising from one-loop pion
graphs in chiral perturbation theory. An asymmetry of ~5 10^{-8} is estimated
for Compton scattering of 100 MeV photons.Comment: 6 pages, 1 figure, latex. Reference adde
Measurement of Partial-Wave Contributions in pp --> pp pi^0
We report a measurement of the spin-dependent total cross section ratios
delta_sigma_T/sigma_tot and delta_sigma_L/sigma_tot of the pp --> pp pi^0
reaction between 325 MeV and 400 MeV. The experiment was carried out with a
polarized internal target in a storage ring. Non-vertical beam polarization was
obtained by the use of solenoidal spin rotators. Near threshold, the knowledge
of both spin-dependent total cross sections is sufficient to deduce the
strength of certain participating partial waves, free of any model.Comment: 6 pages, 4 figure
The Ay Problem for p-3He Elastic Scattering
We present evidence that numerically accurate quantum calculations employing
modern internucleon forces do not reproduce the proton analyzing power, A_y,
for p-3He elastic scattering at low energies. These calculations underpredict
new measured analyzing powers by approximately 30% at E_{c.m.} = 1.20 MeV and
by 40% at E_{c.m.} = 1.69 MeV, an effect analogous to a well-known problem in
p-d and n-d scattering. The calculations are performed using the complex Kohn
variational principle and the (correlated) Hyperspherical Harmonics technique
with full treatment of the Coulomb force. The inclusion of the three-nucleon
interaction does not improve the agreement with the experimental data.Comment: Latex file, 4 pages, 2 figures, to be published on Phys. Rev. Let
The Nucleon Anapole Moment and Parity-Violating ep Scattering
Parity-violating (PV) interactions among quarks in the nucleon induce a PV
coupling, or anapole moment (AM). We compute electroweak
gauge-independent contributions to the AM through {\cal O}(1/\lamchis) in
chiral perturbation theory. We estimate short-distance PV effects using
resonance saturation. The AM contributions to PV electron-proton scattering
slightly enhance the axial vector radiative corrections, R_A^p, over the scale
implied by the Standard Model when weak quark-quark interactions are neglected.
We estimate the theoretical uncertainty associated with the AM contributions to
R_A^p to be large, and discuss the implications for the interpretation PV of ep
scattering.Comment: RevTex 29 pages + 8 PS figures, references and discussions added, to
appear in Phys. Rev.
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