CLAS physics database search results Measurement E151M3 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.55 258 -0.8508 0.346 0.1013 0.55 270 -0.208 0.4244 0.0382 0.65 246 0.2298 0.3859 0.0398 0.65 258 -0.226 0.3728 0.0395 0.65 270 0.3626 0.4804 0.051 0.75 186 0.1708 0.4617 0.0357 0.75 246 -0.1808 0.4561 0.0364 0.75 258 0.0974 0.4512 0.032