CLAS physics database search results Measurement E151M3659 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 270 0.0598 0.2638 0.03 0.85 102 0.4145 0.2072 0.0311 0.85 114 0.0481 0.2476 0.03 0.85 126 -0.1889 0.2613 0.0302 0.85 186 0.2971 0.2612 0.0306 0.85 198 -0.0097 0.2734 0.03