CLAS physics database search results Measurement E151M3358 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 114 0.201 0.2644 0.0303 0.85 222 0.1724 0.2529 0.0302 0.85 234 0.0501 0.2366 0.03 0.65 54 0.5313 0.2361 0.0318