CLAS physics database search results Measurement E151M83 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.45 42 -1.0285 0.6299 0.1208 0.55 246 0.4839 0.7831 0.0627 0.65 234 -0.0714 0.6131 0.0311 0.65 246 0.2113 0.5843 0.0384 0.65 258 -0.6321 0.6526 0.0779 0.75 234 1.0507 0.7419 0.1232 0.75 246 0.8623 0.715 0.1026 0.85 234 0.144 0.661 0.0342 0.85 246 -1.0171 0.5154 0.1195