2019 Workshop on Polarized Sources, Targets, and Polarimetry

Neutron Spin Rotation: Neutron Optical Polarimetry as a Probe of Fundamental Physics

27 Sept 2019, 10:00

20m

Downtown Holiday Inn

Polarization Applications for Fundamental Symmetry Tests Fundamental Symmetry Tests

Speaker

Kyle Steffen (Indiana University)

Description

The Neutron Spin Rotation (NSR) slow neutron polarimeter is an apparatus designed to measure and constrain fundamental interactions to high precision through the use of neutron optical techniques. This apparatus was initially constructed to search for parity-violating spin rotation of neutrons transmitted through liquid ${}^4\text{He}$. This experiment placed a limit on the rotation angle per unit length of $d\varphi /dz=[+2.1\pm 8.3(\mathit{\text{stat.}}){}_{-0.2}^{+2.9}(\mathit{\text{sys.}})]\times {10}^{-7}$ rad/m. This data has been used to constrain light $Z^{\prime }$ bosons, in-matter gravitational torsion, and nonmetricity. A second target system operated with the same polarimeter was designed to search for an axial coupling of neutrons $g_A^2$ to light $Z^{\prime }$ bosons, placing limits on the rotation angle $\varphi =[1.4\pm 2.3(\mathit{\text{stat.}})\pm 2.8(\mathit{\text{sys.}})]\times {10}^{-5}$ rad, improving $g_A^2$ bounds. The polarimeter and targets are being upgraded for future measurements planned for the NG-C beam at NIST Center for Neutron Research. The precision should be sufficient to see the Standard Model contribution to n-${}^4$He spin rotation and improve the limits on $g_A^2$ by about two orders of magnitude. An overview of the apparatus will be presented, along with details of both target systems design and performance. [1]

[1] W. M. Snow, et al., Rev. Sci. Inst. 86, 055101(2015)

Presentation materials

PSTP2019_KyleSteffen.pdf