CLAS physics database search results Measurement E151M1158 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.85 78 0.0699 0.8814 0.0304 0.85 210 2.0517 1.1447 0.1529 0.95 222 -1.1998 0.5809 0.0927 0.95 234 -1.1329 0.6176 0.0881 0.95 246 1.3927 0.9879 0.1061 0.95 258 0.0295 0.7459 0.0301 0.95 270 1.1173 0.9116 0.087