CLAS physics database search results Measurement E151M444 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.55 222 -0.2338 0.7415 0.0333 0.75 234 -1.174 0.6318 0.0786 0.85 222 -0.3372 0.563 0.0366 0.55 234 0.8927 1.2461 0.0616 0.65 234 0.0966 0.9031 0.0306 0.75 234 0.5159 1.2471 0.0432 0.85 234 0.1057 1.0027 0.0307 0.85 246 0.5384 1.1925 0.0442