Examining the d(n,nd) and d(n,np)n Reactions for Evidence of a Three-Nucleon Interaction
A series of experiments has been performed at the Los Alamos Neutron Science Center (LANSCE) by collaborators from the Los Alamos National Laboratory (LANL), the Massachusetts Institute of Technology, the University of Kentucky and Houghton College to examine the possible role of a three nucleon force (3NF) in the strong nuclear interaction. From 1998 to 2002 neutron-deuteron elastic scattering d(n,nd) cross sections were measured in the kinematical region predicted by theory to be most sensitive to contributions from a 3NF. The results of that study motivated measurements of the breakup reaction, d(n,np)n, which theoretical predictions suggested might be even more sensitive to 3NF effects. In each experiment, spallation neutrons were scattered from a liquid deuterium target and outgoing particles were incident on an array of neutron and charged particle detectors. Until 2003, outgoing protons were detected with CsI crystal scintillators and neutrons by either plastic or liquid scintillation detectors. In 2004, several changes were proposed for the detection array, including two permanent magnet charged particle spectrometers and large plastic scintillator bars to detect neutrons. These changes addressed problems discovered in the spring of 2003 with both the experimental setup and the theoretical calculations. Preliminary reaction cross-section results have been obtained for the d(n,nd) reaction, and the d(n,np)n cross-section measurement is planned to begin in August 2005.
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