CLAS physics database search results Measurement E151M365 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.55 222 0.5347 1.1403 0.044 0.55 234 -0.0547 0.5678 0.0335 0.65 222 0.0038 0.6144 0.03 0.65 234 0.1339 0.5711 0.0362 0.75 222 0.7745 1.0962 0.0555 0.75 234 1.4622 0.5591 0.0954