CLAS physics database search results Measurement E151M1644 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 210 -0.4021 0.9142 0.0385 0.65 222 -1.7609 0.8984 0.1097 0.75 222 -1.7603 0.7314 0.1097 0.85 210 -1.0176 0.8745 0.068 0.45 42 -1.5492 1.1825 0.0949 0.65 222 -1.1561 0.8616 0.0736 0.75 210 -1.5762 1.0387 0.0964 0.75 222 1.4708 0.9233 0.0906 0.85 222 -0.7788 1.1794 0.0543