CLAS physics database search results Measurement E151M3625 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 90 0.0731 0.2631 0.03 0.85 210 -0.3313 0.2697 0.0307 0.95 198 -0.3319 0.2662 0.0307 0.95 222 0.0126 0.2741 0.03 0.95 246 -0.4302 0.2431 0.0312