CLAS physics database search results Measurement E151M2895 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 210 -0.1743 0.3549 0.0302 0.45 30 0.175 0.2776 0.0302 0.65 222 0.0923 0.2612 0.0301 0.75 222 -0.1331 0.2814 0.0301