Adhikari D, Albataineh H, Androic D, Aniol K, Armstrong D S, Averett T, Ayerbe Gayoso C, Barcus S, Bellini V, Beminiwattha R S, Benesch J F, Bhatt H, Bhatta Pathak D, Bhetuwal D, Blaikie B, Boyd J, Campagna Q, Camsonne A, Cates G D, Chen Y, Clarke C, Cornejo J C, Covrig Dusa S, Dalton M M, Datta P, Deshpande A, Dutta D, Feldman C, Fuchey E, Gal C, Gaskell D, Gautam T, Gericke M, Ghosh C, Halilovic I, Hansen J-O, Hauenstein F, Henry W, Horowitz C J, Jantzi C, Jian S, Johnston S, Jones D C, Karki B, Kakkar S, Katugampola S, Keppel C E, King P M, King D E, Knauss M, Kumar K S, Kutz T, Lashley-Colthirst N, Leverick G, Liu H, Liyange N, Malace S, Mammei J, Mammei R, McCaughan M, McNulty D, Meekins D, Metts C, Michaels R, Mihovilovic M, Mondal M M, Napolitano J, Nikolaev D, Rashad M N H, Owen V, Palatchi C, Pan J, Pandey B, Park S, Paschke K D, Petrusky M, Pitt M L, Premathilake S, Puckett A J R, Quinn B, Radloff R, Rahman S, Rathnayake A, Reed B T, Reimer P E, Richards R, Riordan S, Roblin Y, Seeds S, Shahinyan A, Souder P A, Tang L, Thiel M, Tian Y, Urciuoli G M, Wertz E W, Wojtsekhowski B, Xiong W, Yale B, Ye T, Zec A, Zhang W, Zhang J, Zheng X
Idaho State University, Pocatello, Idaho 83209, USA.
Texas A & M University - Kingsville, Kingsville, Texas 78363, USA.
Phys Rev Lett. 2022 Apr 8;128(14):142501. doi: 10.1103/PhysRevLett.128.142501.
We report precision determinations of the beam-normal single spin asymmetries (A_{n}) in the elastic scattering of 0.95 and 2.18 GeV electrons off ^{12}C, ^{40}Ca, ^{48}Ca, and ^{208}Pb at very forward angles where the most detailed theoretical calculations have been performed. The first measurements of A_{n} for ^{40}Ca and ^{48}Ca are found to be similar to that of ^{12}C, consistent with expectations and thus demonstrating the validity of theoretical calculations for nuclei with Z≤20. We also report A_{n} for ^{208}Pb at two new momentum transfers (Q^{2}) extending the previous measurement. Our new data confirm the surprising result previously reported, with all three data points showing significant disagreement with the results from the Z≤20 nuclei. These data confirm our basic understanding of the underlying dynamics that govern A_{n} for nuclei containing ≲50 nucleons, but point to the need for further investigation to understand the unusual A_{n} behavior discovered for scattering off ^{208}Pb.
