1. Determination of the ^{27}Al Neutron Distribution Radius from a Parity-Violating Electron Scattering Measurement.
- Author
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Androić D, Armstrong DS, Bartlett K, Beminiwattha RS, Benesch J, Benmokhtar F, Birchall J, Carlini RD, Cornejo JC, Covrig Dusa S, Dalton MM, Davis CA, Deconinck W, Dowd JF, Dunne JA, Dutta D, Duvall WS, Elaasar M, Falk WR, Finn JM, Forest T, Gal C, Gaskell D, Gericke MTW, Gray VM, Grimm K, Guo F, Hoskins JR, Jones DC, Jones MK, Kargiantoulakis M, King PM, Korkmaz E, Kowalski S, Leacock J, Leckey J, Lee AR, Lee JH, Lee L, MacEwan S, Mack D, Magee JA, Mahurin R, Mammei J, Martin JW, McHugh MJ, Meekins D, Mesick KE, Michaels R, Micherdzinska A, Mkrtchyan A, Mkrtchyan H, Narayan A, Ndukum LZ, Nelyubin V, Nuruzzaman, van Oers WTH, Owen VF, Page SA, Pan J, Paschke KD, Phillips SK, Pitt ML, Radloff RW, Rajotte JF, Ramsay WD, Roche J, Sawatzky B, Seva T, Shabestari MH, Silwal R, Simicevic N, Smith GR, Solvignon P, Spayde DT, Subedi A, Suleiman R, Tadevosyan V, Tobias WA, Tvaskis V, Waidyawansa B, Wang P, Wells SP, Wood SA, Yang S, Zang P, Zhamkochyan S, Christy ME, Horowitz CJ, Fattoyev FJ, and Lin Z
- Abstract
We report the first measurement of the parity-violating elastic electron scattering asymmetry on ^{27}Al. The ^{27}Al elastic asymmetry is A_{PV}=2.16±0.11(stat)±0.16(syst) ppm, and was measured at ⟨Q^{2}⟩=0.02357±0.00010 GeV^{2}, ⟨θ_{lab}⟩=7.61°±0.02°, and ⟨E_{lab}⟩=1.157 GeV with the Q_{weak} apparatus at Jefferson Lab. Predictions using a simple Born approximation as well as more sophisticated distorted-wave calculations are in good agreement with this result. From this asymmetry the ^{27}Al neutron radius R_{n}=2.89±0.12 fm was determined using a many-models correlation technique. The corresponding neutron skin thickness R_{n}-R_{p}=-0.04±0.12 fm is small, as expected for a light nucleus with a neutron excess of only 1. This result thus serves as a successful benchmark for electroweak determinations of neutron radii on heavier nuclei. A tree-level approach was used to extract the ^{27}Al weak radius R_{w}=3.00±0.15 fm, and the weak skin thickness R_{wk}-R_{ch}=-0.04±0.15 fm. The weak form factor at this Q^{2} is F_{wk}=0.39±0.04.
- Published
- 2022
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