CLAS physics database search results Measurement E151M1180 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 222 -0.7455 0.8427 0.0622 0.85 90 2.1601 1.143 0.1607 0.85 210 -0.8542 0.786 0.0693 0.95 210 0.7868 0.8712 0.0649 0.95 222 1.3455 0.9628 0.1028 0.95 234 0.015 0.8317 0.03