CLAS physics database search results Measurement E151M3634 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 102 0.1729 0.2369 0.0302 0.85 210 0.133 0.2608 0.0301 0.85 222 0.1907 0.2288 0.0302 0.95 198 -0.4718 0.2389 0.0314