CLAS physics database search results Measurement E151M3653 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 102 -0.2249 0.2299 0.0303 0.85 186 -0.1252 0.2291 0.0301 0.85 198 -0.3216 0.2236 0.0307 0.85 210 -0.0291 0.2841 0.03