EPJ Web Conf.
Volume 219, 2019International Workshop on Particle Physics at Neutron Sources (PPNS 2018)
|Number of page(s)||5|
|Published online||12 December 2019|
Neutron spin rotation measurements
1 Georgia State University, Atlanta, GA 30303, USA
2 Gettysburg College, Gettysburg, PA 17325, USA
3 Indiana University, Bloomington, IN 47408, USA
4 Universidad Nacional Autónoma de México, D.F. 04510, México
5 University of Kentucky, Lexington, KY 40506, USA
6 University of Dayton, Dayton, OH 45469, USA
7 612 S Mitchell St Bloomington, IN 47401, USA
8 University of Virginia, Charlottesville, VA 22903, USA
9 Louisiana State University, Baton Rouge, LA 70803, USA
10 Nagoya University, Furocho, Chikusa Ward, Nagoya, Aichi Prefecture 464-0814, Japan
11 Tennessee Tech University, Cookeville, TN 38505, USA
12 National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
13 Embry-Riddle Aeronautical University, Daytona Beach, FL 32114, USA
14 Los Alamos National Lab, Los Alamos, NM 87545, USA
15 Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra 400085, India
16 University of Washington, Seattle, WA 98105, USA
a e-mail: firstname.lastname@example.org
Published online: 12 December 2019
The neutron spin rotation (NSR) collaboration used parity-violating spin rotation of transversely polarized neutrons transmitted through a 0.5 m liquid helium target to constrain weak coupling constants between nucleons. While consistent with theoretical expectation, the upper limit set by this measurement on the rotation angle is limited by statistical uncertainties. The NSR collaboration is preparing a new measurement to improve this statistically-limited result by about an order of magnitude. In addition to using the new high-flux NG-C beam at the NIST Center for Neutron Research, the apparatus was upgraded to take advantage of the larger-area and more divergent NG-C beam. Significant improvements are also being made to the cryogenic design. Details of these improvements and readiness of the upgraded apparatus are presented. We also comment on how recent theoretical work combining effective field theory techniques with the 1/Nc expansion of QCD along with previous NN weak measurements can be used to make a prediction for dϕ/dz in 4He.
An experiment using the same apparatus with a room-temperature target was carried out at LANSCE to place limits on parity-conserving rotations from possible fifth-force interactions to complement previous studies. We sought this interaction using a slow neutron polarimeter that passed transversely polarized slow neutrons by unpolarized slabs of material arranged so that this interaction would tilt the plane of polarization and develop a component along the neutron momentum. The results of this measurement and its impact on the neutron-matter coupling gA2 from such an interaction are presented. The NSR collaboration is also preparing a new measurement that uses an upgraded version of the room-temperature target to be run on the NG-C beamline; and it is expected to constrain gA2 by at least two additional orders of magnitude for λc between 1 cm and 1 μm.
© The Authors, published by EDP Sciences, 2019
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