CLAS physics database search results Measurement E151M1668 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 222 -0.4093 0.9635 0.0388 0.75 162 -0.7864 0.9189 0.0559 0.75 234 -0.0166 0.9948 0.03 0.75 246 0.3324 0.9016 0.036 0.85 246 -0.5325 0.8645 0.0438 0.55 222 -1.8403 0.7155 0.1111 0.85 222 -0.9748 1.1771 0.0641 0.85 234 -0.3523 0.9334 0.0363 0.85 246 0.8612 0.9669 0.0584