CLAS physics database search results Measurement E151M215 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.65 258 -0.2229 0.3734 0.033 0.75 174 -0.0926 0.4851 0.0305 0.75 234 -0.4715 0.4767 0.0419 0.75 246 0.5479 0.4682 0.0453 0.75 258 -0.2469 0.4003 0.0337 0.85 162 -0.7263 0.4561 0.0541 0.55 258 -0.5749 0.4861 0.0458 0.55 270 -0.1382 0.5942 0.0311 0.65 246 -0.6232 0.4776 0.048 0.65 258 -0.0382 0.588 0.0301 0.75 174 0.5416 0.886 0.0443 0.75 258 0.3539 0.6755 0.0368 0.75 270 0.1817 0.5872 0.0319