CLAS physics database search results Measurement E151M344 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.75 234 1.9364 1.3166 0.1204 0.75 246 0.8289 1.1781 0.0582 0.85 258 1.9144 1.213 0.1191 0.65 246 1.004 0.6987 0.069 0.75 246 0.8994 0.6972 0.0633 0.85 258 0.3558 0.6395 0.0372 0.85 270 1.041 0.6461 0.0711 0.95 258 -0.5589 0.528 0.0458