CLAS physics database search results Measurement E151M904 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 114 -0.588 0.7202 0.0489 0.75 210 0.0536 0.7929 0.0302 0.85 210 2.5922 0.8352 0.1727 0.85 246 1.0298 0.8711 0.0739