A Precision Measurement of the Neutron Scattering Length of He-4 Using Neutron Interferometry
Abstract
We report a 0.08 % measurement of the bound neutron scattering length of 4He using neutron interferometry. The result is b = (3.0982 0.0021 [stat] 0.0014 [sys]) fm. The corresponding free atomic scattering length is a = (2.4746 0.0017 [stat] 0.0011 [sys]) fm. With this result the world average becomes b = (3.0993 0.0025) fm, a 2 % downward shift and a reduction in uncertainty by more than a factor of six. Our result is in disagreement with a previous neutron interferometric measurement but is in good agreement with earlier measurements using neutron transmission.
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