CLAS physics database search results Measurement E151M3149 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.65 210 -0.0555 0.2536 0.03 0.75 234 -0.2295 0.2421 0.0303 0.85 222 -0.2243 0.272 0.0303 0.85 246 0.1358 0.2756 0.0301