CLAS physics database search results Measurement E151M1200 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.65 282 -0.1148 0.8509 0.0312 0.85 90 -0.3169 0.8901 0.0379 0.85 102 0.1527 0.8312 0.032 0.85 114 0.0361 0.8536 0.0301 0.85 198 -0.2259 0.7416 0.0342 0.85 210 -0.6099 0.8529 0.0537 0.85 222 -0.3883 0.8214 0.0413