Neutron-deuteron analyzing power data at 19.0 MeV

Abstract

Measurements of neutron-deuteron (n-d) analyzing power A y (θ) at E n = 19.0 MeV are reported at 16 angles from θ c.m. = 46.7 to 152.0 • . The objective of the experiment is to better characterize the discrepancies between n-d data and the predictions of three-nucleon calculations for neutron energies above 16.0 MeV. The experiment used a shielded neutron source, which produced polarized neutrons via the 2 H( d, n) 3 He reaction, a deuterated liquid scintillator center detector (CD) and liquid-scintillator neutron side detectors. A coincidence between the CD and the side detectors isolated the elastic-scattering events. The CD pulse height spectrum associated with each side detector was sorted by using pulse-shape discrimination, time-of-flight techniques, and by removing accidental coincidences. A Monte Carlo computer simulation of the experiment accounted for effects due to finite geometry, multiple scattering, and CD edge effects. The resulting high-precision data (with absolute uncertainties ranging from 0.0022 to 0.0132) have a somewhat lower discrepancy with the predictions of three-body calculations, as compared to those found at lower energies.

Neutron-deuteron analyzing power data atEn=22.5MeV

“…The lack of n-d A y (θ ) data between 16 and 30 MeV motivated us to perform measurements in this region, to better characterize the energy dependence of the 3N APP and to provide data to aid the theoretical development of NN and 3N potential models. Our measurement of n-d A y (θ ) at E n = 19.0 MeV confirmed the existence of the 3N APP at that energy, with an RD in the vicinity of 25% [19]. In the present work, we confirm the 3N APP at 22.5 MeV, and compare our results to other data, including data for p-d A y (θ ) at 22.7 MeV [20].…”

“…The statistical uncertainties of the new data are about twice as large as those for our data at 19.0 MeV [19]. The data are also displayed in Figs.…”

“…The 19-MeV n-d data of Ref. [19] give an RD of 26% ± 3% (using the AV18 potential). The present 22.5-MeV data give 31% ± 7%, suggesting that the RD does not decrease up to at least E n = 22.5 MeV.…”

“…Because much of the experimental information for the present E n = 22.5 MeV measurement (for example, all of the detector dimensions) are the same as in our earlier 19-MeV measurement [19], we give a shortened treatment here, one that concentrates on the differences between the two. Polarized deuterons were produced by Triangle Universities Nuclear Laboratory's Atomic Beam Polarized Ion Source (ABPIS), accelerated through an FN-tandem accelerator, and deflected by 20 • to the target room.…”

Recent few-body studies at TUNL: Experimental results and challenges

“…New angular distribution measurements of A y in the n-d system have been completed at TUNL at 19 and 22.5 MeV by a group led by G. Weisel 21 , but final data analysis including multiple scattering corrections is still underway. These were made to map out the evolution of A y between the 16 MeV measurements of Sagara et al and the 30 MeV measurements of Dobiasch et al Comparison of these preliminary data with theoretical predictions confirm gradual disappearance of the A y puzzle in n-d scattering as the energy approaches 30MeV.…”