CLAS physics database search results Measurement E151M1679 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 222 0.1559 0.8839 0.0314 0.75 246 -1.5096 0.9693 0.0953 0.65 234 0.4078 1.1095 0.0382 0.75 234 0.7036 1.1575 0.0507 0.85 222 0.5892 1.0952 0.0455