CLAS physics database search results Measurement E151M2677 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 258 -0.145 0.2756 0.0301 0.65 246 0.1754 0.3948 0.0302 0.65 258 -0.7739 0.1893 0.0338 0.75 246 -0.2964 0.3036 0.0306 0.75 258 0.7641 0.1756 0.0337