CLAS physics database search results Measurement E151M1213 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 186 -1.6643 0.6718 0.1253 0.85 114 0.3105 0.7713 0.0376 0.85 126 -1.247 0.741 0.096 0.85 198 -0.3461 0.8375 0.0392