CLAS physics database search results Measurement E151M2827 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.65 126 -0.3954 0.3177 0.031 0.65 246 -0.1851 0.3528 0.0302 0.75 234 -0.07 0.2851 0.03 0.75 258 0.1725 0.3453 0.0302 0.85 258 0.4772 0.279 0.0315 0.55 246 0.2506 0.2706 0.0304 0.85 270 -0.323 0.2625 0.0307 0.95 102 0.4306 0.2618 0.0312