CLAS physics database search results Measurement E151M1474 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 246 -0.22 0.5567 0.034 0.75 234 1.501 0.7124 0.0948 0.65 258 -0.9829 0.6961 0.0646 0.75 246 -1.2639 0.7472 0.0794 0.75 258 -0.3741 0.8853 0.0371 0.85 246 0.7024 0.886 0.0507