CLAS physics database search results Measurement E151M2905 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.55 222 -0.0457 0.2866 0.03 0.65 222 0.1478 0.2646 0.0301 0.55 234 0.8326 0.1947 0.0343 0.75 222 -0.0375 0.3765 0.03 0.75 234 -0.3544 0.3216 0.0308 0.85 222 -0.1138 0.4155 0.0301