CLAS physics database search results Measurement E151M3467 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.35 78 -0.655 0.2075 0.0327 0.75 102 0.5188 0.2118 0.0317 0.75 246 0.2441 0.2467 0.0304 0.75 258 0.1748 0.3047 0.0302 0.85 126 0.0375 0.2833 0.03 0.85 246 0.0048 0.2979 0.03