CLAS physics database search results Measurement E151M3126 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.65 210 -0.2728 0.248 0.0305 0.75 66 0.0162 0.2732 0.03 0.75 270 -0.063 0.2144 0.03 0.85 126 0.34 0.2531 0.0308 0.85 210 0.0183 0.2745 0.03