CLAS physics database search results Measurement E151M3362 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 210 -0.1806 0.237 0.0302 0.75 270 0.2018 0.2665 0.0303 0.85 210 -0.1418 0.2577 0.0301