CLAS physics database search results Measurement E151M249 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.85 114 0.2323 0.5541 0.0333 0.65 282 0.6541 0.9275 0.0495 0.85 270 -0.4519 0.6123 0.0405