Neutron skins of 208Pb and 48Ca from parity-violating scattering · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Neutron skins of 208Pb and 48Ca from parity-violating scattering
Plain
In heavy nuclei the extra neutrons form a thin outer skin whose thickness tells how the pressure of neutron-rich matter rises with density. Two Jefferson Lab experiments give values for lead and calcium that most nuclear models cannot fit at the same time.
Precise · changed · core
Revision 1: PREX-II gives $R_{\mathrm{skin}}(208\mathrm{Pb})$ = $R_{n} - R_{p}$ = 0.283 +/- 0.071 fm and CREX gives $R_{\mathrm{skin}}(48\mathrm{Ca})$ = 0.121 +/- 0.026 (exp) +/- 0.024 (model) fm. Determine whether a single nuclear Hamiltonian or energy density functional reproduces both measured parity-violating asymmetries $A_{\mathrm{PV}}$, and fix $R_{\mathrm{skin}}(208\mathrm{Pb})$ to +/- 0.03 fm. Answer: a consistent description, or the identified experimental or theoretical cause of the tension.
Revision 2: PREX-II gives $R_{\mathrm{skin}}(208\mathrm{Pb})$ = $R_{n} - R_{p}$ = $0.283 \pm 0.071\ \mathrm{fm}$ and CREX gives $R_{\mathrm{skin}}(48\mathrm{Ca})$ = $0.121 \pm 0.026\ (\mathrm{exp}) \pm 0.024\ (\mathrm{model})\ \mathrm{fm}$. Determine whether a single nuclear Hamiltonian or energy density functional reproduces both measured parity-violating asymmetries $A_{\mathrm{PV}}$, and fix $R_{\mathrm{skin}}(208\mathrm{Pb})$ to $\pm 0.03\ \mathrm{fm}$. Answer: a consistent description, or the identified experimental or theoretical cause of the tension.
Settled by
The MREX parity-violating experiment at the Mainz MESA accelerator, planned to reach roughly 0.03 fm on $R_{\mathrm{skin}}(208\mathrm{Pb})$, compared with ab initio predictions of both asymmetries.
Kind
well-posed
Answer type
value
References
(empty)
Literature status
contested
Status note
Ab initio calculations (Hu et al., Nature Physics 2022) predicted $R_{\mathrm{skin}}(208\mathrm{Pb})$ between 0.14 and 0.20 fm, compatible with PREX-II within about 1.5 standard deviations; the joint PREX-II and CREX tension for density functionals persisted as of 2026.
Posed since
2022

Decisions