Showing papers by "Werner Tornow published in 1993"

Complete Set of Deuteron Analyzing Powers in Deuteron-Proton Elastic Scattering: Measurement and Realistic Potential Predictions

Abstract: Tensor analyzing powersiT 11,T 20,T 21 andT 22, have been measured for deuteron laboratory energiesE lab =75, 85, 95, 106, 119, 131, 144, 156, 172, and 187 MeV. The data are compared to rigorous Faddeev calculations with realistic nucleon-nucleon potentials. A generally good description of the data at all energies is obtained.

Dipole and spin-dipole resonances in charge-exchange reactions on 12C.

Abstract: The $^{12}\mathrm{C}$(n,p${)}^{12}$B reaction was studied using the white neutron source at the Los Alamos Meson Physics Facility/Weapon Neutron Research Center with a continuous incident neutron energy from 60 to 260 MeV. Double differential cross sections were measured in the angular range 11\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$\ensuremath{\le}37\ifmmode^\circ\else\textdegree\fi{}. Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility, we also studied the $^{12}\mathrm{C}$(p,n${)}^{12}$N reaction at ${\mathit{E}}_{\mathit{p}}$=186 MeV and the $^{12}\mathrm{C}$(p\ensuremath{\rightarrow},n\ensuremath{\rightarrow}${)}^{12}$N reaction at ${\mathit{E}}_{\mathit{p}\ensuremath{\rightarrow}}$=160 and 186 MeV. Double differential cross sections were measured between ${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$=0\ifmmode^\circ\else\textdegree\fi{} and ${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$=50\ifmmode^\circ\else\textdegree\fi{} in 5\ifmmode^\circ\else\textdegree\fi{} steps. Spin observables ${\mathit{D}}_{\mathit{N}\mathit{N}}$, ${\mathit{A}}_{\mathit{Y}}$, and P were measured at ${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$=5\ifmmode^\circ\else\textdegree\fi{},9\ifmmode^\circ\else\textdegree\fi{},13\ifmmode^\circ\else\textdegree\fi{} with ${\mathit{E}}_{\mathit{p}\ensuremath{\rightarrow}}$=160 MeV and ${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$=15\ifmmode^\circ\else\textdegree\fi{},20\ifmmode^\circ\else\textdegree\fi{} with ${\mathit{E}}_{\mathit{p}\ensuremath{\rightarrow}}$=186 MeV. Angular distributions of differential cross section and spin observables for low-lying transitions in the residual nuclei are compared with disorted-wave impulse approximation (DWIA) calculations. A multipole decomposition analysis was performed to study the giant dipole and giant spin-dipole resonances. The contributions of the quasifree reaction in the giant resonance region was subtracted. The empirical results of energy distributions for dipole (\ensuremath{\Delta}L=1) transition are compared with DWIA calculations using nuclear structure information obtained with a conventional shell model and also with a random phase approximation.

Measurements of polarized-neutron-polarized-proton scattering: Implications for the triton binding energy.

Abstract: Measurements have been made of \ensuremath{\Delta}${\mathrm{\ensuremath{\sigma}}}_{\mathit{T}}$ for polarized neutrons incident on a polarized-proton target from 365 to 1160 MeV In the energy range near 10 MeV, \ensuremath{\Delta}${\mathrm{\ensuremath{\sigma}}}_{\mathit{T}}$ is very sensitive to the nucleon-nucleon tensor interaction Comparison of the data to potential-model predictions indicate that the tensor interaction is weak, resulting in values of the $^{3}$${\mathit{S}}_{1}$${\mathrm{\ensuremath{-}}}^{3}$${\mathit{D}}_{1}$ mixing parameter ${\mathrm{\ensuremath{\epsilon}}}_{1}$ which are smaller than predicted by any nucleon-nucleon potential model A smaller tensor force will bring the predictions of local potential models for the triton binding energy into closer agreement with the experimental value

Neutron scattering from 12C between 15.6 and 17.3 MeV

Abstract: The differential cross section sigma ( theta ) for neutron elastic scattering from 12C and for inelastic scattering from the 4.44 MeV state was measured at 15.57, 16.75 and 17.29 MeV. The sigma ( theta ) data, together with published analysing power Ay( theta ) data, were analysed in the framework of the spherical optical model and in the coupled-channels formalism. It was concluded that the present 12C(n,n)12C data and published data at higher energies appear to be well suited for determining properties of valence single-particle excitations in 11C and 13C via an iterative-moment approach or a dispersive optical-model analysis.

The dispersive optical model for n + 208Pb and n + 209Bi

Abstract: The dispersive optical model (DOM) provides a natural connection between the shell model potential for bound states and the optical model for nucleon scattering at positive energies. At TUNL we have developed DOMs for neutron scattering for ten nuclei between 27Al and 209Bi. In these studies we rely on TUNL measurements of differential cross-section (σ(θ)) and analyzing power, as well as a wealth of σ(θ) and total cross section measurements from numerous other laboratories. In this paper we briefly outline the DOM method and the achievements in describing scattering data for n + 208Pb and n + 209Bi and single-particle bound-state data for neutrons in 208Pb.

Novel probe of charge symmetry breaking: Deuteron-induced deuteron breakup.

Abstract: The present paper identifies unique symmetry properties of the [ital [rvec d]]+[ital d][r arrow][ital d]+[ital p]+[ital n] breakup reaction that make it an excellent probe for studying charge-symmetry breaking. Measurements were made for two configurations of the ejected particles in the breakup reaction to obtain values of the spin observables [ital A][sub [ital y]], [ital A][sub [ital y][ital y]], and [ital A][sub [ital z][ital z]]. These observables are compared for the mirror reactions [sup 2]H([ital [rvec d]],[ital dp])[ital n] and [sup 2]H([ital [rvec d]],[ital dn])[ital p] for the two angle pairs ([theta][sub [ital d]],[phi][sub [ital d]],[theta][sub [ital N]],[phi][sub [ital N]])=(17.0[degree],0[degree],17.0[degree],180[degree]) and (17.0[degree],0[degree],34.5[degree],180[degree]) for an incident deutron energy of 12 MeV. In addition, spin observables for the [sup 2]H([ital [rvec d]],[ital pn])[ital d] reaction at [theta][sub [ital p]]=[theta][sub [ital n]] and [phi][sub [ital p]]=[phi][sub [ital n]]+180[degree] are shown to provide a particularly good test of charge symmetry. Our [ital A][sub [ital y]], [ital A][sub [ital y][ital y]], and [ital A][sub [ital z][ital z]] data for the [sup 2]H([ital [rvec d]],[ital pn])[ital d] reaction at ([theta][sub [ital p]],[phi][sub [ital p]],[theta][sub [ital n]],[phi][sub [ital n]])=(17.0[degree],0[degree],17.0[degree],180[degree]) are used to illustrate this latter point. Of the ten charge-symmetric sets of observables measured, two were foundmore » to differ by 2.5 standard deviations.« less