CLAS physics database search results Measurement E151M3515 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 114 -0.1379 0.2548 0.0301 0.75 126 -0.2447 0.2532 0.0304 0.85 222 0.0951 0.2868 0.0301 0.85 234 -0.2845 0.2199 0.0305