68 research outputs found
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
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
Experimental search for evidence of the three-nucleon force and a new analysis method
A research program with the aim of investigating the spin dependence of the
three-nucleon continuum in pd collisions at intermediate energies was carried
out at IUCF using the Polarized INternal Target EXperiments (PINTEX) facility.
In the elastic scattering experiment at 135 and 200 MeV proton beam energies a
total of 15 independent spin observables were obtained. The breakup experiment
was done with a vector and tensor polarized deuteron beam of 270 MeV and an
internal polarized hydrogen gas target. We developed a novel technique for the
analysis of the breakup observables, the sampling method. The new approach
takes into account acceptance and non-uniformities of detection efficiencies
and is suitable for any kinematically complete experiment with three particles
in the final state.Comment: Contribution to the 19th European Few-Body Conference, Groningen Aug.
23-27, 200
Spin correlations in pion production near threshold
A first measurement of longitudinal as well as transverse spin correlation
coefficients for the reaction was made using a
polarized proton target and a polarized proton beam. We report kinematically
complete measurements for this reaction at 325, 350, 375 and 400 MeV beam
energy. The spin correlation coefficients and the analyzing power as well as angular
distributions for and the polarization observables
were extracted. Partial wave cross sections for dominant
transition channels were obtained from a partial wave analysis that included
the transitions with final state angular momenta of . The measurements
of the polarization observables are compared
with the predictions from the J\"ulich meson exchange model. The agreement is
very good at 325 MeV, but it deteriorates increasingly for the higher energies.
At all energies agreement with the model is better than for the reaction
.Comment: Preprint, 21 pp, submitted to Phys. Rev. C. Keywords: Mesons,
Polarization, Spin Correlations, Few body system
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.
Report on CE-19: 16-O(p,n)16-F(0-) in the IUCF Cooler
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Toy Model for Pion Production II: The role of three-particle singularities
The influence of three-particle breakup singularities on s-wave meson
production in nucleon-nucleon collisions is studied within the distorted wave
Born approximation. This study is based on a simple scalar model for the
two-nucleon interaction and the production mechanism. An algorithm for the
exact numerical treatment of the inherent three-body cuts, together with its
straightforward implementation is presented. It is also shown that two
often-used approximations to avoid the calculation of the three-body breakup
are not justified. The possible impact on pion production observables is
discussed.Comment: 14 pages, 6 figure
Differential Cross Section and Analyzing Power of p(p,pi+)d Near Threshold
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Towards a field theoretic understanding of NN->NNpi
We study the production amplitude for the reaction NN->NNpi up to
next--to--leading order in chiral perturbation theory using a counting scheme
that takes into account the large scale introduced by the initial momentum. In
particular we investigate a subtlety that arises once the leading loop
contributions are convoluted with the NN wavefunctions as demanded by the
non--perturbative nature of the NN interaction. We show how to properly
identify the irreducible contribution of loop diagrams in such type of
reaction. The net effect of the inclusion of all next-to-leading order loops is
to enhance the leading rescattering amplitude by a factor of 4/3, bringing its
contribution to the cross section for pp->dpi+ close to the experimental value.Comment: 15 Pages, 5 Figure
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