CLAS physics database search results Measurement E151M1933 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 210 -0.8893 0.8139 0.0617 0.65 210 -2.1737 0.6312 0.1351 0.75 198 -1.5283 0.7343 0.0973 0.75 210 -0.8273 0.7798 0.0584 0.75 258 -0.3775 0.8345 0.0377 0.75 270 -0.7016 0.741 0.052 0.75 282 0.4455 0.788 0.0404 0.85 126 -0.1949 0.7509 0.0322 0.85 210 -0.6719 0.7458 0.0506