2H(n,p)2n experiment to measure accurately the neutron-neutron scattering length.211 Final report for reporting period May 1, 1995-October 31, 1998

摘要

The neutron-neutron (n-n) scattering length a(sub nn) is a parameter that211u001erepresents the strength of the n-n interaction at low energies. It can be 211u001ecompared with the proton-proton (p-p) scattering length a(sub pp) to investigate 211u001ethe charge-symmetry breaking in nuclear forces. The difference a(sub pp)-a(sub 211u001enn) is a measure of the mass difference of the up and down quarks and therefore 211u001eit is of fundamental interest. Experiments to determine a(sub nn) use mainly one 211u001eof two deuteron reactions: Pi -d capture or Pi -d breakup. For both of these 211u001edeuteron reactions, a (sub nn) is extracted by analysis of the crosssection data. 211u001eHowever, the experimental values of a(sub nn) from the two reactions disagree. 211u001eWhat is more confusing than this discrepancy is that significantly different 211u001evalues for a(sub nn) are reported from similar (sup 2)H(n,p) 2n experiments. This 211u001eproblem must be resolved before the differences between Pi -d and n-d reactions 211u001ecan be addressed further.