CLAS physics database search results Measurement E151M3590 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 66 0.2691 0.26 0.0305 0.85 186 -0.1099 0.2818 0.0301 0.85 210 0.2 0.2726 0.0303 0.85 246 -0.411 0.2236 0.0311 0.95 234 -0.7362 0.2109 0.0334 0.95 246 -0.7632 0.1853 0.0337 0.95 270 -0.7215 0.1831 0.0333 0.95 294 -0.0545 0.2556 0.03