CLAS physics database search results Measurement E151M1215 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 270 1.7737 0.9899 0.1331 0.85 102 0.0366 0.7853 0.0301 0.85 114 0.1277 0.841 0.0314 0.85 126 1.827 1.0729 0.1369 0.85 186 -1.3769 0.7129 0.105 0.85 198 1.2286 1.0433 0.0947