CLAS physics database search results Measurement E151M2222 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 102 0.0724 0.8539 0.0305 0.75 258 0.1404 0.8864 0.0317 0.75 318 -0.3268 0.7737 0.0382 0.85 234 0.3331 0.7773 0.0385 0.85 258 0.412 0.9112 0.0423 0.85 270 1.0766 0.7502 0.0836