V. Huhn et al., New investigation of the neutron-neutron and neutron-proton final-state interaction in the n-d breakup reaction - art. no. 014003, PHYS REV C, 6301(1), 2001, pp. 4003
The neutron-neutron final-state interaction (FSI) has been investigated in
the H-2(n,np)n reaction at 25.3 and 16.6 MeV, detecting neutrons and proton
s in coincidence in a geometry which should enable a practically model-inde
pendent determination of the S-1(o) neutron-neutron scattering length a(nn)
. The analysis was performed by means of detailed Monte Carlo simulations b
ased on rigorous three-body calculations with realistic nucleon-nucleon pot
entials. At 25.3 MeV, the value of a,, deduced from the absolute cross sect
ion in the FSI peak is - -16.3+/-0.4 fm while the relative cross section, n
ormalized in the region of neutron-proton quasifree scattering, gives - 16.
1+/-0.4 fm. The relative data obtained at 16.6 MeV yielded a(nn) = - 16.2+/
-0.3 fm. In addition, the S-1(o) neutron-proton scattering length was measu
red at 25.2 MeV in the same configuration for comparison. While our results
for a(nn) are incompatible with those of a similar investigation performed
recently at 13 MeV where the two neutrons were detected, both results for
a(np) are in good agreement with the accurately known value from free n-p s
cattering.