CLAS physics database search results Measurement E151M855 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 102 -0.3175 0.5696 0.0365 0.75 246 0.6037 0.6895 0.0497 0.85 66 0.0007 0.5842 0.03 0.85 246 -0.3949 0.5592 0.0396 0.85 270 0.062 0.6162 0.0303 0.65 102 -0.8424 1.54 0.0833 0.85 270 -0.6158 1.4071 0.0643 0.95 294 3.3057 4.2099 0.3066