CLAS physics database search results Measurement E151M649 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.65 102 0.6327 0.8967 0.049 0.75 234 0.1853 0.8135 0.0321 0.85 78 0.5753 0.8594 0.0462 0.85 246 0.3452 0.6954 0.0367 0.85 258 -0.3915 0.6997 0.0384 0.95 222 1.5027 0.7336 0.0967 0.95 234 1.3434 0.7753 0.0875