CLAS physics database search results Measurement E151M3125 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 246 0.353 0.2418 0.0308 0.85 210 -0.3035 0.2705 0.0306 0.85 234 0.1526 0.2461 0.0302 0.95 102 0.4938 0.2342 0.0316