August 29, 2022 to September 4, 2022
America/New_York timezone

Neutral Weak Form Factor Measurements from the PREX-II and CREX Experiments

Sep 2, 2022, 10:30 AM
30m
Palm Ballroom 3 ,

Palm Ballroom 3 ,

Parallel session talk Precision Physics at High Intensities HI: Precision Physics at High Intensities

Speaker

Allison Zec (University of New Hampshire)

Description

PREX-II and CREX were two experiments designed to measure the neutron skin thickness in $^{208}$Pb and $^{48}$Ca respectively. Both experiments used the parity-violating electron scattering (PVES) technique, which involved measuring the parity-violating cross-section asymmetry ($A_{pv}$) between left- and right-handed longitudinally polarized electron scattering off an unpolarized target. The neutron radius of each nucleus is then extracted from the weak form factor which is itself extracted from $A_{pv}$. Obtaining an accurate measurement of $A_{pv}$ is technically challenging because of the small size of $A_{pv}$, (on the order of 1 ppm for both $^{208}$Pb and $^{48}$Ca) as well as sources of noise and false asymmetries that may arise from beam instabilities and the polarimetry measurement. Additionally, both experiments had to be designed to accomodate high-Z targets, which means constructing detectors capable of high-rate measurement, as well as engineered radiation controls to protect experimental equipment. A number of experimental systems were constructed and deployed to minimize the contributions from source of false asymmetry, and make the measurement of $A_{pv}$ technically feasible. PREX-II's measured $A_{pv}$ for $^{208}$Pb is 550 ± 16 (stat) ± 8 (syst) ppb and CREX's measured $A_{pv}$ for $^{48}$Ca is 2668 ± 106 (stat) ± 40 (syst) ppb. This corresponds to a neutron skin thickness for $^{208}$Pb of 0.278 ± 0.078 (exp) ± 0.012 (theo) fm and a skin thickness for $^{48}$Ca of 0.121 ± 0.026 (exp) ± 0.024 (theo).

Primary author

Allison Zec (University of New Hampshire)

Presentation materials