CLAS physics database search results Measurement E151M3150 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 210 0.0746 0.2763 0.03 0.75 294 -0.3487 0.2672 0.0308 0.85 222 -0.2129 0.2396 0.0303 0.85 234 -0.3571 0.2227 0.0308 0.85 246 0.1243 0.2401 0.0301