CLAS physics database search results Measurement E151M931 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 270 0.3213 0.7301 0.0422 0.85 102 1.2258 1.0567 0.117 0.85 114 -0.1086 0.8597 0.0316 0.65 138 -1.3123 0.5112 0.0912 0.65 210 0.8317 0.6949 0.0623 0.85 102 -1.0777 0.5545 0.0768