CLAS physics database search results Measurement E151M195 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.35 54 -0.2412 0.7103 0.0407 0.55 246 1.3044 0.7715 0.1514 0.65 234 -0.6251 0.6732 0.0772 0.65 246 -0.6679 0.4617 0.0817 0.65 258 -0.6181 0.5192 0.0765 0.75 246 0.672 0.7236 0.0821 0.75 258 0.0576 0.5945 0.0307 0.85 246 -0.4446 0.6404 0.0588 0.85 258 0.3694 0.575 0.0516 0.85 270 1.0228 0.7484 0.1202