CLAS physics database search results Measurement E151M2914 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.65 282 -0.2526 0.2421 0.0304 0.75 270 0.1782 0.2639 0.0302 0.95 114 0.0169 0.2573 0.03 0.95 126 -0.2691 0.2242 0.0305 0.95 138 0.1463 0.2831 0.0301