CLAS physics database search results Measurement E151M3651 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 114 0.0116 0.2484 0.03 0.85 126 -0.1254 0.2266 0.0301 0.85 186 0.2319 0.2579 0.0304 0.85 198 0.111 0.2827 0.0301 0.85 210 -0.1579 0.2502 0.0302