We report a determination of the n-He3 scattering length difference Δb′=b1′-b0′=[-5.411±0.031(statistical)±0.039(systematic)] fm between the triplet and singlet states using a neutron interferometer. This revises our previous result Δb′=[-5.610±0.027(statistical)±0.032(systematic)] fm obtained using the same technique in 2008 [Huber, Phys. Rev. Lett. 102, 200401 (2009)10.1103/PhysRevLett.102.200401; Huber, Phys. Rev. Lett. 103, 179903(E) (2009)10.1103/PhysRevLett.103.179903]. This revision is attributable to a reanalysis of the 2008 experiment that now includes a systematic correction caused by magnetic-field gradients near the He3 cell which had been previously underestimated. Furthermore, we more than doubled our original data set from 2008 by acquiring 6 months of additional data in 2013. Both the new data set and a reanalysis of the older data are in good agreement. Scattering lengths of low-Z isotopes are valued for use in few-body nuclear effective field theories, provide important tests of modern nuclear potential models, and, in the case of He3, aid in the interpretation of neutron scattering from quantum liquids. The difference Δb′ was determined by measuring the relative phase shift between two incident neutron polarizations caused by the spin-dependent interaction with a polarized He3 target. The target He3 gas was sealed inside a small, flat-windowed glass cell that was placed in one beam path of the interferometer. The relaxation of He3 polarization was monitored continuously with neutron transmission measurements. The neutron polarization and spin-flipper efficiency were determined separately using He3 analyzers and two different polarimetry analysis methods. A summary of the measured scattering lengths for n-He3 with a comparison to nucleon interaction models is given.
ASJC Scopus subject areas
- Nuclear and High Energy Physics