He Target System*

The rotation of a polarized neutron’s spin in liquid ⁴He provides experimental access to parity-violation in the nucleon-nucleon weak interaction (NNWI). Recent work in NNWI theory [1] [2] [3] has lead to a predicted value of the neutron spin rotation (NSR) angle in ⁴He of dφ/dz = 6.8×10⁻⁷ rad/m [4]. Previous experimental analysis from the NSR collaboration gives statistically-limited results at this order of magnitude. A new non-magnetic pump and target system, as well as interim upgrades to the NSR apparatus, are expected to achieve experimental sensitivity < [±1.0(stat.) ± 1.0(sys.)]×10⁻⁷ rad/m [5] on the NG-C beam at NIST – allowing for the first standard model test in the NNWI sector. The status of the NSR apparatus will be presented, with emphasis on the ongoing assembly of the target system.

References

[1] D. R. Phillips, D. Samart, and C. Schat, Phys. Rev. Lett. 114, 062301(2015).

[2] D. Samart, C. Schat, M. R. Schindler, and D. R. Phillips, Phys. Rev. C 94, 024001 (2016).

[3] M. R. Schindler, R. P. Springer, and J. Vanasse, Phys. Rev. C 93, 025502 (2016).

[4] S. Gardner, W. C. Haxton, and B. R. Holstein, Ann. Rev. Nucl. Part. Sci. 67, 69 (2017).

[5] W. M. Snow, Et Al., Rev. Sci. Inst. 86, 055101(2015)