CLAS physics database search results Measurement E151M3373 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 270 0.0515 0.2315 0.03 0.75 282 -0.1009 0.1717 0.0301 0.85 114 0.0044 0.243 0.03 0.85 126 0.611 0.1934 0.0324 0.85 210 -0.1314 0.2485 0.0301