CLAS physics database search results Measurement E151M682 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.65 210 -0.6231 0.6137 0.0485 0.75 66 0.7399 0.7591 0.0543 0.75 270 1.068 0.586 0.0719 0.85 126 -0.5088 0.6579 0.0432 0.85 210 -0.0596 0.681 0.0302