W. W. Daehnick’s research while affiliated with University of Pittsburgh and other places

The proton and deuteron analyzing powers and ten 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.

We have measured the vector and tensor polarization of an atomic deuterium target as a function of the target density. The polarized deuterium was produced in an atomic beam source and injected into a storage cell. For this experiment, the atomic beam source was operated without rf transitions, in order to avoid complications from the unknown efficiency of these transitions. In this mode, the atomic beam is vector and tensor polarized and both polarizations can be measured simultaneously. We used a 1.2-cm-diam and 27-cm-long storage cell, which yielded an average target density between 3 and 9×1011at/cm3. We find that the tensor polarization decreases with increasing target density while the vector polarization remains constant. The data are in quantitative agreement with the calculated effect of spin exchange between deuterium atoms at low field.

We have measured the spin-dependent total cross sections Delta sigmaT and Delta sigma_L, the spin correlation parameters A_xx, A_yy, A_xz and A_zz, and beam and target analyzing power in p d arrow t pi^+ at beam energies of 250 and 275 MeV. The experiment was carried out at the IUCF Cooler ring using a cooled, vertically or longitudinally polarized proton beam, and an internal, vector polarized deuterium target. The target polarization was switched between the vertical (±y), horizontal (±x) and longitudinal (±z) direction. The experiment is the first measurement of spin correlation observables in pion production in the three nucleon system. Preliminary results will be discussed.

The PINTEX atomic beam source, which was previously used to produce a polarized, internal hydrogen target for measurements of spin correlation coefficients in pp elastic scattering and pion production, was modified to also produce a polarized deuterium target. The target thickness obtained with a 12mm diameter and 25cm long storage cell is on the order of 1013 atoms/cm2. Two new transition units with variable gradient were installed to facilitate easy changeover from hydrogen to deuterium target. The ABS is capable of producing pure vector polarization with a theoretical maximum value of +2/3 and pure tensor polarization of theoretical maximal values of +/-1. The direction of the vector polarization can be reversed by reversing the direction of the holding field at the target. To date, this internal deuterium target has been used for a measurement of spin correlation coefficients in pd elastic scattering.

A first measurement of longitudinal as well as transverse spin correlation coefficients for the reaction p⃗p⃗→pnπ+ is 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 energies. The spin correlation coefficients Axx+Ayy, Axx-Ayy, Azz, and Axz and the analyzing power Ay, as well as angular distributions for σ(θπ) and the polarization observables Aij(θπ), are extracted. Partial wave cross sections for dominant transition channels are obtained from a partial-wave analysis that included transitions with final-state angular momenta of l<~1. The measurements of the p⃗p⃗→pnπ+ polarization observables are compared with the predictions from the Jülich 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 p⃗p⃗→ppπ0.

This version is available at the following Publisher URL: http://prc.aps.org

Pion production in pp collisions is of special interest near threshold where very few partial waves contribute and where calculations should be manageable and results more conclusive. The first explicit calculations for pp --> pppi0 and pp --> pnpi+ cross sections near threshold were made by Koltun and Reitan in 1966 and by Schillaci, Silbar and Young in 1969. They remained unchallenged and untested until cross sections very close to threshold could finally be measured1,2. The realization that the pioneering calculations missed the true cross sections by a wide margin has spurred much new theoretical research.3,4,5 ...

In a kinematically complete experiment we have measured the two analyzing powers and the five spin correlation coefficients of pp arrow pp π^0 as a function of all five parameters of the three-body final state for bombarding energies between 325 and 400 MeV. The experiment was carried out at the Indiana Cooler Storage Ring. Below 400 MeV, a total of 12 complex partial-wave amplitudes are significant. We have developed a formalism for an expansion of the spin observables of a reaction with polarized spin-1/2 collision partners and a three-body final state into a complete set of angular functions. We use this expansion to completely describe the polarization information obtainable in neutral pion production by colliding polarized protons.

In a kinematically complete experiment we have measured the two analyzing powers and the five spin correlation coefficients of the reaction p→p→ → pp π0 as a function of all five parameters of the three-body final state for bombarding energies between 325 and 400 MeV. The data are in disagreement with the theoretical predictions available at this time. Below 400 MeV, fewer than a dozen complex partial-wave amplitudes are likely to be significant, and it is expected that the present experimental information constrains these amplitudes. We also describe the formalism for an expansion of the spin observables into a complete set of angular functions and use this to completely characterize the polarization information obtainable from reactions with polarized spin-1/2 collision partners and a three-body final state.

The spin correlation coefficent combinations A(xx)+A(yy) and A(xx)-A(yy), the spin correlation coefficients A(yz) and A(zz), and the analyzing power were measured for (p) over right arrow (p) over right arrow-->d pi(+) between center-of-mass angles 25 degrees less than or equal to theta less than or equal to 65 degrees at beam energies of 350.5, 375.0, and 400.0 MeV. The experiment was carried out with a polarized internal target and a stored, polarized beam. Nonvertical beam polarization needed for the measurement of A(zz) was obtained by the use of solenoidal spin rotators. Near threshold, only a few partial waves contribute, and pion s and p waves dominate with a possible small admixture of d waves. Certain combinations of the observables reported here are a direct measure of these d waves. The d-wave contributions are found to be negligible even at 400.0 MeV.