CLAS physics database search results Measurement E151M3368 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 102 0.3889 0.2304 0.031 0.85 126 -0.0529 0.2649 0.03 0.85 210 -0.0041 0.2534 0.03 0.65 294 -0.094 0.2577 0.0301 0.85 114 0.222 0.2611 0.0303 0.85 234 -0.5742 0.1991 0.0321