Androić D, Armstrong D S, Asaturyan A, Bartlett K, Beaufait J, Beminiwattha R S, Benesch J, Benmokhtar F, Birchall J, Carlini R D, Cornejo J C, Dusa S Covrig, Dalton M M, Davis C A, Deconinck W, Dowd J F, Dunne J A, Dutta D, Duvall W S, Elaasar M, Falk W R, Finn J M, Forest T, Gal C, Gaskell D, Gericke M T W, Grames J, Gray V M, Grimm K, Guo F, Hoskins J R, Jones D, Jones M K, Jones R T, 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, Mei J, Mesick K E, Michaels R, Micherdzinska A, Mkrtchyan A, Mkrtchyan H, Morgan N, Narayan A, Ndukum L Z, Nelyubin V, van Oers W T H, 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, Suleiman R, Tadevosyan V, Tobias W A, Tvaskis V, Waidyawansa B, Wang P, Wells S P, Wood S A, Yang S, Zang P, Zhamkochyan S
University of Zagreb, Zagreb, HR 10002, Croatia.
William & Mary, Williamsburg, Virginia 23185, USA.
Phys Rev Lett. 2020 Sep 11;125(11):112502. doi: 10.1103/PhysRevLett.125.112502.
A beam-normal single-spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable related to the imaginary part of the two-photon exchange process. We report a 2% precision measurement of the beam-normal single-spin asymmetry in elastic electron-proton scattering with a mean scattering angle of θ_{lab}=7.9° and a mean energy of 1.149 GeV. The asymmetry result is B_{n}=-5.194±0.067(stat)±0.082 (syst) ppm. This is the most precise measurement of this quantity available to date and therefore provides a stringent test of two-photon exchange models at far-forward scattering angles (θ_{lab}→0) where they should be most reliable.
在非极化核子与横向极化电子散射过程中产生的束流法线单自旋不对称性是一个与双光子交换过程虚部相关的可观测量。我们报告了在弹性电子 - 质子散射中束流法线单自旋不对称性的2%精度测量结果，平均散射角为θ_{lab}=7.9°，平均能量为1.149 GeV。不对称性结果为B_{n}=-5.194±0.067(统计)±0.082(系统)ppm。这是迄今为止该量最精确的测量，因此为双光子交换模型在远前向散射角(θ_{lab}→0)提供了一个严格测试，在该角度模型应该最可靠。
