Measurement of the Beam-Normal Single-Spin Asymmetry for Elastic Electron Scattering from \(^{12}\)C and \(^{27}\)Al

• Published in: arXiv.org 2021-06
• Main Authors: Collaboration, QWeak, Androic, D, Armstrong, D S, Asaturyan, A, Bartlett, K, Beminiwattha, R S, Benesch, J, Benmokhtar, F, Birchall, J, Carlini, R D, Christy, M E, Cornejo, J C, S Covrig Dusa, Dalton, M M, Davis, C A, Deconinck, W, Dowd, J F, Dunne, J A, Dutta, D, Duvall, W S, Elassar, M, Falk, W R, Finn, J M, est, T, Gal, C, Gaskell, D, Gericke, M T W, Gray, V M, Guo, F, Hoskins, J R, Jones, D C, Kargiantoulakis, M, King, P M, Korkmaz, E, Kowalski, S, Leacock, J, Leckey, J P, Lee, A R, Lee, J H, Lee, L, MacEwan, S, Mack, D, Magee, J A, Mahurin, R, Mammei, J, Martin, J W, McHugh, M J, Meekins, D, Mesick, K E, Michaels, R, Mkrtchyan, A, Mkrtchyan, H, Narayan, A, Ndukum, L Z, Nuruzzaman, Nelyubin, V, W T H van Oers, Owen, V F, Page, S A, Pan, J, Paschke, K D, Phillips, S K, Pitt, M L, Radloff, R W, Rajotte, J F, Ramsay, W D, Roche, J, Sawatzky, B, Seva, T, Shabestari, M H, Silwal, R, Simicevic, N, Smith, G R, Solvignon, P, Spayde, D T, Subedi, A, Subedi, R, Tadevosyan, V, Tobias, W A, Waidyawansa, B, Wang, P, Wells, S P, Wood, S A, Zang, P, Zhamkochyan, S
• Format: Article
• Language: English
• Subjects: Asymmetry; Elastic scattering; Electron beams; Electron spin; Scattering angle
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2103.09758

We report measurements of the parity-conserving beam-normal single-spin elastic scattering asymmetries \(B_n\) on \(^{12}\)C and \(^{27}\)Al, obtained with an electron beam polarized transverse to its momentum direction. These measurements add an additional kinematic point to a series of previous measurements of \(B_n\) on \(^{12}\)C and provide a first measurement on \(^{27}\)Al. The experiment utilized the Qweak apparatus at Jefferson Lab with a beam energy of 1.158 GeV. The average lab scattering angle for both targets was 7.7 degrees, and the average \(Q^2\) for both targets was 0.02437 GeV\(^2\) (Q=0.1561 GeV). The asymmetries are \(B_n\) = -10.68 \(\pm\) 0.90 stat) \(\pm\) 0.57 (syst) ppm for \(^{12}\)C and \(B_n\) = -12.16 \(\pm\) 0.58 (stat) \(\pm\) 0.62 (syst) ppm for \(^{27}\)Al. The results are consistent with theoretical predictions, and are compared to existing data. When scaled by Z/A, the Q-dependence of all the far-forward angle (theta < 10 degrees) data from \(^{1}\)H to \(^{27}\)Al can be described by the same slope out to \(Q \approx 0.35\) GeV. Larger-angle data from other experiments in the same Q range are consistent with a slope about twice as steep.