Experimental upper bound and theoretical expectations for parity-violating neutron spin rotation in 4He

H E Swanson; B R Heckel; C D Bass; T D Bass; J M Dawkins; J C Horton; D Luo; W M Snow; S B Walbridge; B E Crawford; K Gan; A M Micherdzinska; C Huffer; D M Markoff; H P Mumm; J S Nico; M Sarsour; E I Sharapov; V Zhumabekova

doi:10.1103/PhysRevC.100.015204

Experimental upper bound and theoretical expectations for parity-violating neutron spin rotation in ⁴He

Phys Rev C. 2019;100(1):10.1103/PhysRevC.100.015204. doi: 10.1103/PhysRevC.100.015204.

Authors

H E Swanson¹, B R Heckel¹, C D Bass², T D Bass³, J M Dawkins³, J C Horton³, D Luo³, W M Snow³, S B Walbridge³, B E Crawford⁴, K Gan⁵, A M Micherdzinska⁵, C Huffer⁶, D M Markoff⁷, H P Mumm⁸, J S Nico⁸, M Sarsour⁹, E I Sharapov¹⁰, V Zhumabekova¹¹

Affiliations

¹ University of Washington and Center for Experimental Nuclear Physics and Astrophysics, Box 354290, Seattle, Washington 98195, USA.
² LeMoyne College, 1419 Salt Springs Road, Syracuse, New York 13214, USA.
³ Indiana University and Center for the Exploration of Energy and Matter, 2401 Milo B. Sampson Lane, Bloomington, Indiana 47408, USA.
⁴ Gettysburg College, 300 North Washington Street, Gettysburg, Pennsylvania 17325, USA.
⁵ The George Washington University, 2121 I Street N.W., Washington, DC 20052, USA.
⁶ North Carolina State University, 2401 Stinson Drive, Raleigh, North Carolina 27695, USA.
⁷ North Carolina Central University/TUNL, 1801 Fayetteville Street, Durham, North Carolina 27707, USA.
⁸ National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA.
⁹ Georgia State University, 29 Peachtree Center Avenue, Atlanta, Georgia 30303-4106, USA.
¹⁰ Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Russia.
¹¹ Al-Farabi Kazakh National University, Al-Farabi Avenue 71, 050038 Almaty, Kazakhstan.

Abstract

Neutron spin rotation is expected from quark-quark weak interactions in the standard model, which induce weak interactions among nucleons that violate parity. We present the results from an experiment searching for the effect of parity violation via the spin rotation of polarized neutrons in a liquid ⁴He medium. The value for the neutron spin rotation angle per unit length in ⁴He, $d ϕ / d z = [+ 2.1 \pm 8.3 {(stat.)}_{- 0.2}^{+ 2.9} (sys.)] \times 10^{- 7}$ rad/m, is consistent with zero. The result agrees with the best current theoretical estimates of the size of nucleon-nucleon weak amplitudes from other experiments and with the expectations from recent theoretical approaches to weak nucleon-nucleon interactions. In this paper we review the theoretical status of parity violation in the $\vec{n} +$ ⁴He system and discuss details of the data analysis leading to the quoted result. Analysis tools are presented that quantify systematic uncertainties in this measurement and that are expected to be essential for future measurements.

Grants and funding

9999-NIST/ImNIST/Intramural NIST DOC/United States