CLAS physics database search results Measurement E151M2788 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 234 0.5907 0.2657 0.0322 0.75 246 -0.2939 0.4042 0.0306 0.85 258 0.3036 0.3117 0.0306 0.65 246 -0.542 0.2552 0.0319 0.75 246 0.0041 0.2816 0.03 0.85 258 0.0409 0.2595 0.03 0.85 270 -0.099 0.276 0.0301 0.95 258 -0.3314 0.2436 0.0307