Precision neutron interferometric measurement of the n-{sup 3}He coherent neutron scattering length
- North Carolina State University, Raleigh, North Carolina 27695 (United States)
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8461 (United States)
- University of Missouri-Columbia, Columbia, Missouri 65211 (United States)
- University of North Carolina at Wilmington, Wilmington, North Carolina 28403-3297 (United States)
- Indiana University/IUCF, Bloomington, Indiana 47408 (United States)
A measurement of the n-{sup 3}He coherent scattering length using neutron interferometry is reported. The result, b{sub c}=(5.8572{+-}0.0072) fm, improves the measured precision of any single measurement of b{sub c} by a factor of eight; the previous world average, b{sub c}=(5.74{+-}0.04) fm, now becomes b{sub c}=(5.853{+-}0.007) fm. Measurements of the n-p, n-d, and n-{sup 3}He coherent scattering lengths have now been performed using the same technique, thus allowing one to extract the scattering length ratios: parameters that minimize systematic errors. We obtain values of b{sub n{sup 3}}{sub He}/b{sub np}=(-1.5668{+-}0.0021) and b{sub nd}/b{sub np}=(-1.7828{+-}0.0014). Using the new world average value of b{sub c} and recent high-precision spin-dependent scattering length data also determined by neutron optical techniques, we extract new values for the bound singlet and triple scattering lengths of b{sub 0}=(9.949{+-}0.027) fm and b{sub 1}=(4.488{+-}0.017) fm for the n-{sup 3}He system. The free nuclear singlet and triplet scattering lengths are a{sub 0}=(7.456{+-}0.020) fm and a{sub 1}=(3.363{+-}0.013) fm. The coherent scattering cross section is {sigma}{sub c}=(4.305{+-}0.007) b and the total scattering cross section is {sigma}{sub s}=(5.837{+-}0.014) b. Comparisons of a{sub 0} and a{sub 1} to the only existing high-precision theoretical predictions for the n-{sup 3}He system, calculated using a resonating group technique with nucleon-nucleon potentials incorporating three-nucleon forces, have been performed. Neutron scattering length measurements in few-body systems are now sensitive enough to probe small effects not yet adequately treated in present theoretical models.
- OSTI ID:
- 20695574
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 70, Issue 1; Other Information: DOI: 10.1103/PhysRevC.70.014004; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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