Neutron-deuteron analyzing power data at 19.0 MeV


Measurements of neutron-deuteron (n-d) analyzing power Ay(θ) at En=19.0 MeV are reported at 16 angles from θc.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 H2(d-,n-)He3 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. © 2010 The American Physical Society.






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Publication Info

Weisel, GJ, W Tornow, BJ Crowe, AS Crowell, JH Esterline, CR Howell, JH Kelley, RA Macri, et al. (2010). Neutron-deuteron analyzing power data at 19.0 MeV. Physical Review C - Nuclear Physics, 81(2). p. 24003. 10.1103/PhysRevC.81.024003 Retrieved from

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Werner Tornow

Professor Emeritus of Physics

Professor Werner Tornow became the Director of TUNL in July, 1996. He is primarily interested in studying few-nucleon systems with special emphasis on two-nucleon systems and three-nucleon force effects in three-nucleon systems. Polarized beams and polarized targets are essential in this work. He collaborates with the leading theoreticians in his field to interpret the experimental data obtained at TUNL. He recently became involved in weak-interaction physics, especially in double-beta decay studies and in neutrino oscillation physics using large scale detectors at the Kamland project in Japan.


Alex Crowell

Research Scientist, Senior

Calvin R. Howell

Professor of Physics

Professor Howell’s research is in the area of experimental nuclear physics with emphasis on the quantum chromodynamics (QCD) description of low-energy nuclear phenomena, including structure properties of nucleons and nuclei and reaction dynamics in few-nucleon systems.   The macroscopic properties of nucleon structure and the residual strong nuclear force between neutrons and protons in nuclei emerge from QCD at distances where the color interactions between quarks and gluons are strong.  However, the details of the mechanisms that generate the strong nuclear force are not well understood.   Effective field theories (EFT) and Lattice QCD calculations provide theoretical frames that connect low-energy nuclear phenomena to QCD.  Professor Howell and collaborators are conducting experiments on few-nucleon systems that test predictions of ab-initio theory calculations for the purpose of providing insight about the QCD descriptions of low-energy nucleon interactions and structure.  His current projects include measurements of the electromagnetic and spin-dependent structure properties of nucleons via Compton scattering on the proton and few-nucleon systems and studies of two- and three-nucleon interactions using few-nucleon reactions induced by photons and neutrons.  In the coming years, a focus will be on investigating the neutron-neutron interaction in reactions and inside nuclei.  In addition, his work includes applications of nuclear physics to national nuclear security, medical isotope production, and plant biology. Most of his research is carried out at the High Intensity Gamma-ray Source and the tandem laboratory at TUNL. 

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