A New Measurement of the 1S0 Neutron-Neutron Scattering Length using the Neutron-Proton Scattering Length as a Standard
Abstract
The present paper reports high-accuracy cross-section data for the 2H(n,nnp) reaction in the neutron-proton (np) and neutron-neutron (nn) final-state-interaction (FSI) regions at an incident mean neutron energy of 13.0 MeV. These data were analyzed with rigorous three-nucleon calculations to determine the 1S0 np and nn scattering lengths, anp and ann. Our results are ann = -18.7 +/- 0.6 fm and anp = -23.5 +/- 0.8 fm. Since our value for anp obtained from neutron-deuteron (nd) breakup agrees with that from free np scattering, we conclude that our investigation of the nn FSI done simultaneously and under identical conditions gives the correct value for ann. Our value for ann is in agreement with that obtained in pion-deuteron capture measurements but disagrees with values obtained from earlier nd breakup studies.
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