CLAS physics database search results Measurement E151M914 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.85 114 0.4889 1.308 0.0542 0.85 222 -1.485 0.9399 0.1403 0.85 234 1.7503 1.0654 0.1643 0.65 54 1.1538 0.6583 0.0814