CLAS physics database search results Measurement E151M2413 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.85 90 -1.1629 0.9579 0.0895 0.85 102 -0.6955 1.0858 0.0587 0.85 186 0.6694 1.2047 0.0571 0.85 198 -1.4217 0.9483 0.1074 0.85 210 -1.2885 0.8939 0.0981 0.85 222 -0.9384 0.9138 0.0744 0.85 234 -1.3733 0.9936 0.104 0.95 210 0.149 1.0105 0.0319 0.95 222 -0.2833 0.9591 0.0364