CLAS physics database search results Measurement E151M179 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.35 42 -0.3758 0.7627 0.0522 0.55 258 0.4375 0.6815 0.0581 0.65 234 -0.8029 0.6858 0.0962 0.65 258 -0.311 0.6257 0.0464 0.75 246 -0.7655 0.6157 0.0921 0.75 258 1.094 0.7071 0.128 0.85 234 0.8031 0.7716 0.0962 0.85 258 1.7737 0.6992 0.204