CLAS physics database search results Measurement E151M470 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.65 282 0.0424 0.4719 0.0301 0.75 270 -0.7521 0.403 0.0549 0.95 114 0.9186 0.4708 0.0637 0.95 126 -0.1465 0.391 0.0313 0.95 138 -0.1978 0.4717 0.0323