CLAS physics database search results Measurement E151M695 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.65 222 0.4398 0.6155 0.0403 0.75 198 0.3367 0.5798 0.0364 0.75 210 0.0454 0.6073 0.0301 0.75 270 -0.4551 0.5016 0.0409 0.85 138 -0.061 0.6242 0.0302