CLAS physics database search results Measurement E151M199 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.65 258 1.1165 0.8965 0.0736 0.65 270 -0.6857 0.4181 0.051 0.85 162 -0.7932 0.4046 0.0564 0.85 198 1.1118 0.9296 0.0734 0.55 270 0.1099 0.4669 0.0308 0.75 174 -0.2031 0.4202 0.0325 0.75 258 0.102 0.4592 0.0307 0.85 186 -0.0829 0.4271 0.0304