Differential scattering cross-section data have been measured at 43 angles from 11 deg. to 160 deg. for 37-MeV neutrons incident on {sup 209}Bi. The primary motivation for the measurements is to address the scarcity of neutron scattering data above 30 MeV and to improve the accuracy of optical-model predictions at medium neutron energies. The high-statistics measurements were conducted at the China Institute of Atomic Energy using the {sup 3}H(d,n){sup 4}He reaction as the neutron source, a pulsed deuteron beam, and time-of-flight (TOF) techniques. Within the resolution of the TOF spectrometer, the measurements included inelastic scattering components. The sum of elastic and inelastic scattering cross sections was computed in joint optical-model and distorted-wave Born approximation calculations under the assumption of the weak particle-core coupling. The results challenge predictions from well-established spherical optical potentials. Good agreement between data and calculations is achieved at 37 MeV provided that the balance between surface and volume absorption in a recent successful model [A. J. Koning and J. P. Delaroche, Nucl. Phys. A 713, 231 (2003)] is modified, thus suggesting the need for global optical-model improvements at medium neutron energies.

We present new corrections for the polarization-dependent efficiency (PDE), which introduces a false asymmetry into measurements of n-p analyzing power A(y)(theta) caused by double scattering in the neutron side detectors. To accomplish this, we created a new database of C-12((n) over right arrow, n) A(y)(theta) by using a combination of fits to data, phase-shift analysis, and R-matrix analysis. Our recorrection for PDE of previously reported n-p A(y)(theta) data at 7.6 and 12.0 MeV and new data at 7.6 MeV indicate that we have achieved a superior representation of C-12((n) over right arrow, n). Our results continue to suggest a possible charge dependence of the pion-nucleon coupling constant.

We present the most accurate and complete data set for the analyzing power Ay(θ) in neutron–proton scattering. The experimental data were corrected for the effects of multiple scattering, both in the center detector and in the neutron detectors. The final data at En=12.0 MeV deviate considerably from the predictions of nucleon–nucleon phase-shift analyses and potential models. The impact of the new data on the value of the charged pion–nucleon coupling constant is discussed in a model study.

Cross-section measurements of seven exit-channel configurations in the neutron-deuteron breakup at 13.0 MeV are reported and compared to rigorous calculations. Our data are consistent with those of previous measurements in four of six configurations. The present data for five configurations are in good agreement with theoretical predictions. The cross-section data for the space-star and another out-of-plane configuration are larger than the theoretical predictions by more than three standard deviations. The previously observed 20% discrepancy between theory and data for the space-star configuration is confirmed in the present work. The inclusion of the Tucson-Melbourne 2 pi-exchange three-nucleon force changes the predicted cross section by only 2% and in the wrong direction needed to bring theory into agreement with data.

The analyzing power ${A}_{y}(\ensuremath{\theta})$ for neutron elastic scattering from $^{12}\mathrm{C}$ has been measured for 33 neutron energies between ${E}_{n}=2.2$ and 8.5 MeV in the angular range from 25${}^{\ifmmode^\circ\else\textdegree\fi{}}$ to 145${}^{\ifmmode^\circ\else\textdegree\fi{}}$ in the laboratory system. The primary motivation for these measurements is the need for an accurate knowledge of ${A}_{y}(\ensuremath{\theta})$ for $^{12}\mathrm{C}$$(n,n)$$^{12}\mathrm{C}$ elastic scattering to enable corrections to high-precision neutron-proton and neutron-deuteron ${A}_{y}(\ensuremath{\theta})$ data in the neutron-energy range below ${E}_{n}=30$ MeV. In their own right, $^{12}\mathrm{C}$$(n,n)$$^{12}\mathrm{C}$ ${A}_{y}(\ensuremath{\theta})$ data are of crucial importance for improving both the parametrization of $n\text{\ensuremath{-}}$$^{12}\mathrm{C}$ scattering and our knowledge of the level scheme of $^{13}\mathrm{C}$. The present ${A}_{y}(\ensuremath{\theta})$ data are compared with published data and previous phase-shift-analysis results.

The analyzing power A(y)(theta) for neutron elastic scattering from C-12 has been measured for 33 neutron energies between E-n=2.2 and 8.5 MeV in the angular range from 25(degrees) to 145(degrees) in the laboratory system. The primary motivation for these measurements is the need for an accurate knowledge of A(y)(theta) for C-12(n,n)C-12 elastic scattering to enable corrections to high-precision neutron-proton and neutron-deuteron A(y)(theta) data in the neutron-energy range below E-n=30 MeV. In their own right, C-12(n,n)C-12 A(y)(theta) data are of crucial importance for improving both the parametrization of n-C-12 scattering and our knowledge of the level scheme of C-13. The present A(y)(theta) data are compared with published data and previous phase-shift-analysis results.

Differential cross sections sigma(theta) and analyzing powers A(y)(theta) have been measured for neutron scattering from Al-27 and Co-59 at 15 MeV at the Triangle Universities Nuclear Laboratory using standard time-of-flight techniques. In addition, sigma(theta) was measured for Co-59 at 10, 12, 14, 17, and 19 MeV. Two large databases covering the energy range from 0.1 to 80 MeV were formed for these nuclei from this new data and previously published data, including that for the total cross section sigma(T). These sets of data were analyzed using spherical dispersive optical-model (DOM) potentials, as well as coupled-channels model (CCM) potentials. The Co-59 DOM gives good agreement with the sigma(theta) data, except in the region of the first minimum. It also gives a reasonable description of our A(y)(theta) measurement. The Al-27 DOM gives good agreement with the data, except for sigma(theta) at backward angles below 9.4 MeV and for sigma(T), for which there is up to 5% disagreement in the 10-50 MeV range. Compared to the DOM, the Co-59 CCM calculations give improved agreement with the sigma(theta) data, especially at the first minimum. The sigma(T) calculations agree with the data to within about 3% above 1.0 MeV. The three-level CCM calculations for Al-27 give excellent agreement with the entire database.

Cross-section measurements of a collinear configuration, the space-star and the coplanar-star configurations in nd breakup at En = 13.0 MeV are reported. The present measurements for the collinear configuration are in good agreement with pd and nd data. Our coplanar-star data are consistent with theoretical predictions and resolve the reported problem with this configuration. The previously observed large discrepancy between theory and nd cross-section data for the space-star configuration is confirmed in the present work.

A review of kinematically incomplete {ital n}-{ital d} breakup data and their comparison to rigorous 3{ital N} calculations using realistic nucleon-nucleon interactions revealed unexplained differences of more than 25{percent} in regions where a large number of different three-nucleon configurations contribute to the cross section. {copyright} {ital 1996 The American Physical Society.}

Results of kinematically-complete cross-section measurements of the n — d breakup reaction at E n = 13 MeV are reported. The new data for the space-star configuration of the three outgoing nucleons are in good agreement with previous data but are considerably different from rigorous n — d calculations. A status report on our n — n and n — p FSI measurements is given. New information about the importance of three-nucleon force effects in the n — d reaction is expected from these data. New data for the analyzing power in n — p scattering at E n = 12 MeV are presented. The preliminary analysis of these accurate data does not support the small value obtained by the Nijmegen group for the charged πN N coupling constant.

We review published analyses of the final-state-interaction enhancement observed in proton energy distributions obtained from kinematically incomplete neutron-deuteron breakup experiments. We compare the results derived from these analyses for the neutron-neutron scattering length, a nn , with our results based on a rigorous treatment of the three-nucleon Faddeev equations in conjunction with the use of realistic nucleon-nucleon potentials. Our values for a nn deviate outside the quoted uncertainties from the ones obtained in the previous analyses where simplified nucleon-nucleon interaction models were employed. In contrast to the previous determinations, the present results for a nn are in clear disagreement with the values for a nn based on π−-deuteron capture experiments. Unless inconsistencies in the experimental neutron-deuteron breakup data at low energies can be resolved and the neutron-deuteron breakup data at low energies can be resolved and the influence of possible three-nucleon-force effects can be reliably determined, we recommend that one not resort to the kinematically incomplete neutron-deuteron breakup reaction as a tool for determining a quantity as important for nuclear and particle physics as is the neutron-neutron scattering length a nn .

Recent reanalysis of scattering data by the Nijmegen group has led to new values for the πNN coupling constants, g2π°/4π and g2π±/4π, about 6% smaller than the previously accepted values. The impact of this finding is far reaching. Since the neutron‐proton Ay(θ) is dominated at low energies by the one‐pion‐exchange mechanism, accurate np data should provide unique information as to the magnitude of g2π±/4π. Using a new experimental setup consisting of a shielded neutron source, a five‐pair neutron detector array, a n‐4He polarimeter, and an intense polarized source with fast spin‐flipping capability, we have measured a 15 point angular distribution of the neutron‐proton Ay(θ) at and incident neutron energy of 12 MeV to a statistical accuracy of 5×10−4. We will discuss the data taking procedures, the analysis, and the corrections applied to the data. Preliminary results will be presented.

Results of our recent kinematically complete cross-section measurements of the space-star and coplanar-star configurations in n-d breakup at 13.0 MeV are reported. The experimental setup and details of the analysis are described. The new data for the space-star configuration are in good agreement with previous n-d data but differ significantly from both “exact” n-d calculations and p-d data. In constrast, the new coplanar-star data are in fair agreement with the calculations but are in gross disagreement with previous n-d data. The implications of these data for three-nucleon forces are discussed.

High-accuracy differential cross-section data for neutron-deuteron elastic scattering at centre-of-mass backward angles in the range from 140° to 178° have been measured to accuracies better than ±3% for incident neutron energies of 8.0, 10.0, and 14.0 MeV. The measurements were made by detection of the recoil deuterons and protons from a mixed CD2-CH2 foil. The new data are compared to existing data and to three-nucleon calculations with the Bonn-B nucleon-nucleon potential. We conclude that the present measurements unambiguously resolve the discrepancies among previously reported data of the same type.