CLAS physics database search results Measurement E151M705 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.65 210 2.2446 2.2446 0.1405 0.75 234 -0.0909 0.5616 0.0305 0.85 222 -0.2784 0.578 0.0345 0.85 246 0.2151 0.6208 0.0328