CLAS physics database search results Measurement E151M1936 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 210 -0.5501 0.8123 0.0448 0.75 222 0.6616 0.8187 0.0501 0.75 270 -0.7092 0.7693 0.0524 0.85 198 -0.3691 0.7398 0.0374 0.85 210 -1.6277 0.7068 0.1031 0.85 222 -1.1088 0.7388 0.0736