CLAS physics database search results Measurement E151M1046 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.55 90 -0.0274 0.7892 0.0301 0.65 114 -1.4334 0.5554 0.109 0.65 234 0.2545 0.8749 0.0353 0.75 102 1.0177 0.9348 0.0802 0.75 258 1.1936 0.8565 0.0923 0.75 282 1.5366 0.8751 0.1162 0.85 246 0.5799 0.774 0.0519 0.85 294 -0.9763 0.4882 0.0774 0.85 306 0.0091 0.7088 0.03 0.95 282 -0.4241 0.6236 0.0431