CLAS physics database search results Measurement E151M455 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.75 222 1.0351 0.6926 0.0708 0.75 234 -0.2762 0.8619 0.0343 0.85 222 1.5715 1.457 0.0993 0.85 234 -0.7394 0.7812 0.0537