CLAS physics database search results Measurement E151M1672 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.85 222 -0.3174 0.969 0.0355 0.85 234 -0.3878 0.8155 0.038 0.85 246 -0.4755 0.8375 0.0414 0.75 234 1.1234 1.0606 0.0719 0.85 246 1.3479 0.9531 0.0839