CLAS physics database search results Measurement E151M3159 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 222 0.4176 0.2323 0.0311 0.75 282 -0.1242 0.2507 0.0301 0.85 126 0.2154 0.2738 0.0303 0.85 210 0.034 0.2833 0.03 0.85 222 0.0193 0.2814 0.03