Showing papers by "Werner Tornow published in 1990"

Proton mean field in 40Ca between -60 MeV and +200 MeV deduced from a dispersive optical-model analysis.

Abstract: The {ital p}-{sup 40}Ca mean field is derived from an optical-model (OM) analysis that explicitly incorporates the dispersion relation connecting the real and imaginary parts of the mean field. This analysis is based on differential cross-section, analyzing power, and reaction cross-section data available in the energy range between 20 and 180 MeV. The extrapolation of the OM potential from positive to negative energies provides the shell-model potential. This extrapolation is guided by known single-particle energies. The deeply bound 1{ital p} and 1{ital s} orbits clearly indicate the need for a linear rather than an exponential energy dependence of the Hartree-Fock potential at large negative energies. The analysis also provides root-mean-square radii, occupation probabilities, spectral functions, and absolute spectroscopic factors for proton single-particle orbits in {sup 40}Ca. Our calculated 15% depletion of the hole states in {sup 40}Ca is lower than that suggested for {sup 208}Pb from theoretical and experimental studies. We also find that a substantial amount of single-particle strength in {sup 40}Ca is located at rather high excitation energy.

Techniques for vector analyzing power measurements of the 2H(n, np)n breakup reaction at low energies

Abstract: Experimental methods to measure the vector analyzing powers over a broad range of kinematic configurations in the n-d breakup reaction have been developed at TUNL. These techniques employ the polarized beam facilities at TUNL and use the 2H( d , n )3He reaction as a source of low-energy polarized neutrons. Our methods permit measurements to a high statistical accuracy over a large fraction of three-nucleon phase space. The techniques are described and experimental spectra along with kinematic calculations are presented.

Sensitivity ofn-p scattering observables to charge-independence breaking of the3P N-N phase shifts

Abstract: The sensitivity of neutron-proton scattering observables to the recently reported charge-independence breaking of the isospinT=13P nucleon-nucleon interaction has been calculated. It is shown that only the analyzing powerA y (θ) at extreme forward angles and at θ=90° c.m. and the spin-correlation coefficientA zx (θ) at 90° c.m. exhibit a measurable sensitivity. It is concluded that the determination ofA y at 90° c.m. is currently the most accurate approach to verify independently charge-independence breaking in the3P nucleon-nucleon phase shifts, considering the status of present experimental techniques.