CLAS physics database search results Measurement E151M1493 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 234 1.3391 1.013 0.0834 0.65 246 0.3765 0.8329 0.0371 0.65 258 -0.1985 0.7157 0.0321 0.75 246 -0.0197 0.9205 0.03 0.85 246 1.6986 0.6491 0.1032 0.55 246 -0.4263 0.7206 0.0394 0.65 234 -0.5436 0.6699 0.0443 0.65 258 0.1146 0.726 0.0308 0.75 234 -0.0037 0.695 0.03 0.75 246 -0.2503 0.6063 0.0335