CLAS physics database search results Measurement E151M2022 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.85 102 0.9816 0.826 0.0705 0.85 258 1.3989 0.7029 0.0958 0.85 282 0.1254 0.7609 0.0311 0.85 294 -0.2736 0.6928 0.0349 0.95 294 -0.0451 1.1365 0.0301