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Neutron Skin Measurement of208Pb Using Parity-Violating Electron Scattering
Department: Physics
ResourceLengthWidthThickness
Paper000
Specimen Elements
Pocatello
Unknown to Unknown
Devi L. Adhikari
Idaho State University
Dissertation
No
7/29/2021
digital
City: Pocatello
Doctorate
Nuclear stability requires large nuclei to have more neutrons than protons. While the central core of the nucleus is composed of symmetric nuclear matter, the extra neutrons in heavy nuclei are pushed out to the surface of the nucleus, forming a pure outer neutron skin layer. While the proton distribution inside a nucleus hasbeen accurately measured using electromagnetic probes, previous measurements ofneutron distributions in complex nuclei have suffered a lack of systematic preci-sion. PREX-2 and CREX use Parity-Violating electron Scattering (PVeS), as an electro weak interaction probe, to measure the neutron distributions in208Pb and48Ca, respectively. Making use of elastic scattering of longitudinally polarized elec-trons from unpolarized (isotopically pure) targets, PREX-2 and CREX measure the asymmetry in scattering rates between opposite beam polarization states. Since both experiments share the same exact measurement concept and apparatus, much of this dissertation applies to both PREX-2 and CREX. However, the presented asymmetry analysis and neutron skin extraction are only for PREX-2. PREX-2 measures the parity-violating asymmetry, APV, for 953 MeV electrons scattered elastically from208Pb at∼5°in the lab. The final result isAPV= 550.00±16.09(stat.)±8.16(syst.)ppb. From this measurement, we report the neutron skin thickness in208Pb nuclei to be, Rskin= 0.278±0.078(exp.)±0.012(model) fm. This measurement has broad implications throughout the physics community, increasing our knowledge in neutron star structure, the equation of state of nuclear matter, nuclear baryon density, nuclear electric dipole polarizability, and more. Key Words: Neutron skin, electroweak interaction, PREX-2, CREX, parity-violating asymmetry, neutron star, quartz detector, weak charge radius, symmetry energy, HallA, Jefferson Lab

Neutron Skin Measurement of208Pb Using Parity-Violating Electron Scattering

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