Measurement of the parity-odd angular distribution of γ rays from polarized neutron capture on Cl35

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Abstract

We report a measurement of two energy-weighted γ cascade angular distributions from polarized slow neutron capture on the Cl35 nucleus, one parity-odd correlation proportional to sn - ·kγ - and one parity-even correlation proportional to sn - ·kn - ×kγ - . A parity-violating asymmetry can appear in this reaction due to the weak nucleon-nucleon interaction, which mixes opposite parity S- and P-wave levels in the excited compound Cl36 nucleus formed upon slow neutron capture. If parity-violating (PV) and parity-conserving (PC) terms both exist, the measured differential cross section can be related to them via dσdω 1+Aγ,PVcosθ+Aγ,PCsinθ. The PV and PC asymmetries for energy-weighted γ cascade angular distributions for polarized slow neutron capture on Cl35 averaged over the neutron energies from 2.27-9.53 meV were measured to be Aγ,PV=(-23.9±0.7)×10-6 and Aγ,PC=(0.1±0.7)×10-6. These results are consistent with previous experimental results. Systematic errors were quantified and shown to be small compared to the statistical error. These asymmetries in the angular distributions of the γ rays emitted from the capture of polarized neutrons in Cl35 were used to verify the operation and data analysis procedures for the NPDGamma experiment, which measured the parity-odd asymmetry in the angular distribution of γs from polarized slow neutron capture on protons.

Original languageEnglish
Article number015504
JournalPhysical Review C
Volume106
Issue number1
DOIs
StatePublished - Jul 2022

Bibliographical note

Funding Information:
We gratefully acknowledge the support of the U.S. Department of Energy Office of Nuclear Physics through Grants DE-AC52-06NA25396, DE-FG02-03ER41258, DE-SC0014622, DE-AC-02-06CH11357, DE-AC05-00OR22725, and DE-SC0008107, the U.S. National Science Foundation through Grants PHY-1306547, PHY-1306942, PHY-1614545, PHY-0855584, PHY-0855610, PHY-1205833, PHY-1506021, PHY-1205393, and PHY-0855694, PAPIIT-UNAM Grants IN110410, IN11193, and IG1011016, CONACYT Grant 080444, the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Canadian Foundation for Innovation (CFI). This research used resources of the Spallation Neutron Source of Oak Ridge National Laboratory, a DOE Office of Science User Facility. J.F., R.C.G., J.M., W.M.S., and Z.T. acknowledge support from the Indiana University Center for Spacetime Symmetries. S. Schröder acknowledges support from the German Academic Exchange Service (DAAD).

Publisher Copyright:
© 2022 American Physical Society.

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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