CLAS physics database search results Measurement E151M2894 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 222 0.214 0.2771 0.0303 0.85 234 -0.1279 0.2383 0.0301 0.85 246 -0.2244 0.2486 0.0303 0.75 234 0.2693 0.3289 0.0305 0.85 246 0.1968 0.3336 0.0303