CLAS physics database search results Measurement E151M715 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 222 2.5471 2.5471 0.1587 0.75 282 0.1872 0.664 0.0321 0.85 126 1.4852 0.804 0.0957 0.85 210 -0.2873 0.6982 0.0348 0.85 222 -0.1864 0.7045 0.0321