CLAS physics database search results Measurement E151M2150 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 210 -0.148 0.8418 0.0315 0.75 270 0.1637 0.689 0.0318 0.75 282 -0.4252 0.6349 0.0408 0.85 114 -0.946 0.7102 0.0685 0.85 210 0.0995 0.8183 0.0307 0.45 270 -0.5871 0.7477 0.0617 0.85 114 1.0098 1.1117 0.0975 0.85 126 -0.453 1.047 0.0513 0.85 210 -0.8362 1.081 0.0825