The pNab experiment and the quest for ever better neutron beam polarization

Journal Article · Sun Jun 22 00:00:00 EDT 2025 · PoS - Proceedings of Science

DOI:https://doi.org/10.22323/1.472.0066· OSTI ID:2573432

Baessler, Stefan; Alarcon, Ricardo; Barrón Palos, Libertad; Broussard, Leah J.; Choi, Jin H.; Chupp, Tim; Crawford, Chris B.; Dodson, George; FOMIN, Nadia; Fry, Jason; Gonzalez, Frank; Hamblen, Josh; Hayen, Leendert; Jezghani, Aaron; Makela, Mark; Mammei, Russ; Mendelsohn, August; Mueller, Paul E.; Penttila, Seppo; Pioquinto, Jason A. ; Plaster, Brad; Pocanic, Dinko; Saunders, Andy; Schreyer, Wolfgang; Young, Albert R.

The Nab and pNAB collaborations are conducting a program of studies of free neutron beta decay, with the primary goal of testing the unitarity of the Cabbibo-Kobayashi-Maskawa matrix that describes quark mixing due to the weak interaction. For this purpose, a large, novel electromagnetic spectrometer, the Nab spectrometer, has been designed, built, and placed in use to determine the correlation coefficients in unpolarized neutron beta decay: 𝑎, the neutrino–electron correlation coefficient; and 𝑏, the Fierz term. The subject of this paper is pNAB, the second phase of the program, that will deploy the same spectrometer with a polarized neutron beam to determine 𝐴, the beta asymmetry; and 𝐵, the neutrino asymmetry coefficients. A focus of this paper will be on the strategies to provide a high and precisely known neutron beam polarization.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• Contributing Organization: pNAB Collaboration
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 2573432
• Alternate ID(s): OSTI ID: 2909372
• Journal Information: PoS - Proceedings of Science, Journal Name: PoS - Proceedings of Science Vol. 472
• Publisher: Sissa Medialab
• Country of Publication: United States
• Language: English