CLAS physics database search results Measurement E151M1132 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.85 234 1.8636 0.869 0.1395 0.85 246 -0.4205 0.623 0.0429 0.85 258 -0.1778 0.6849 0.0327 0.95 234 -0.3729 0.629 0.0405 0.95 306 0.9054 0.7215 0.0727