We report a precise measurement of the parity-violating (PV) asymmetry APV in the elastic scattering of longitudinally polarized electrons from Ca48. We measure APV=2668±106(stat)±40(syst) parts per billion, leading to an extraction of the neutral weak form factor FW(q=0.8733 fm-1)=0.1304±0.0052(stat)±0.0020(syst) and the charge minus the weak form factor Fch-FW=0.0277±0.0055. The resulting neutron skin thickness Rn-Rp=0.121±0.026(exp)±0.024(model) fm is relatively thin yet consistent with many model calculations. The combined CREX and PREX results will have implications for future energy density functional calculations and on the density dependence of the symmetry energy of nuclear matter.

Original languageEnglish
Article number042501
JournalPhysical Review Letters
Issue number4
StatePublished - 22 Jul 2022
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2022 American Physical Society.


We thank the entire staff of JLab for their efforts to develop and maintain the polarized beam and the experimental apparatus and acknowledge the support of the U.S. Department of Energy, the National Science Foundation, and NSERC (Canada). We thank J. Piekarewicz, P. G. Reinhard, and X. Roca-Maza for RPA calculations of excited states and J. Erler and M. Gorchtein for calculations of radiative corrections. This material is based upon the work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics Contract No. DE-AC05-06OR23177.

FundersFunder number
National Science Foundation
U.S. Department of Energy
Office of Science
Nuclear PhysicsDE-AC05-06OR23177
Natural Sciences and Engineering Research Council of Canada


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