CLAS physics database search results Measurement E151M2422 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 282 0.3705 0.9928 0.0403 0.85 90 -0.7268 1.0507 0.0606 0.85 102 -0.6153 0.9301 0.0538 0.85 114 -0.6354 0.9726 0.055 0.85 198 -0.0751 0.8807 0.0305 0.85 210 1.1104 1.0434 0.0859 0.85 222 -0.302 0.994 0.0371