CLAS physics database search results Measurement E151M1071 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 114 -0.3758 0.8127 0.0407 0.75 126 0.345 0.9242 0.0392 0.85 222 0.921 1.0233 0.0737 0.85 234 1.3279 0.8787 0.1016