CLAS physics database search results Measurement E151M3455 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 78 -0.1529 0.236 0.0302 0.75 90 0.1748 0.2718 0.0302 0.75 258 -0.003 0.2619 0.03 0.75 306 -0.591 0.2243 0.0322 0.85 270 -0.2644 0.2762 0.0305 0.85 282 -0.0689 0.2729 0.03