CLAS physics database search results Measurement E151M103 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.55 246 -0.358 0.6676 0.0506 0.65 234 -0.244 0.7339 0.0409 0.65 246 1.5298 0.8068 0.1766 0.75 246 -0.9142 0.6045 0.1082