CLAS physics database search results Measurement E151M1904 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 210 -1.7225 0.6798 0.1086 0.75 66 -1.0999 0.7609 0.0731 0.75 270 0.1678 0.6317 0.0317 0.85 126 1.248 0.7593 0.0814 0.85 210 -0.6165 0.7958 0.0479