CLAS physics database search results Measurement E151M1305 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.45 42 -0.5826 0.8202 0.0722 0.55 246 1.7474 0.7645 0.1994 0.65 234 0.8008 0.6927 0.0952 0.65 246 -0.1488 0.6557 0.0344 0.65 258 -0.5116 0.7811 0.065 0.75 234 0.2992 0.8116 0.0452 0.75 246 0.9021 0.7656 0.1061 0.85 234 0.1391 0.7427 0.0339 0.85 246 0.6636 0.6802 0.0806