CLAS physics database search results Measurement E151M1550 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 222 -0.5999 0.7204 0.0466 0.65 222 0.2341 0.8687 0.0331 0.65 234 -0.1918 0.725 0.0321 0.75 234 -0.1292 0.792 0.031 0.55 246 0.2131 0.9769 0.0325 0.65 210 -1.3425 1.0951 0.0836 0.65 222 -1.5581 0.7592 0.0954 0.85 222 0.8167 1.0588 0.0562 0.85 234 1.2365 0.7423 0.0779