CLAS physics database search results Measurement E151M2568 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.65 54 0.0035 0.2156 0.03 0.75 222 0.0574 0.2381 0.03 0.75 234 -0.1777 0.2375 0.0302 0.75 246 -0.2733 0.2402 0.0305 0.85 234 0.0825 0.2573 0.03