CLAS physics database search results Measurement E151M446 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.65 222 1.6267 0.6382 0.1051 0.75 162 -1.1011 0.7005 0.0745 0.75 234 0.9214 0.716 0.0645 0.75 246 -0.8832 0.677 0.0624 0.85 246 0.381 0.6559 0.0382 0.55 222 -0.1951 0.9123 0.0322 0.85 222 1.0097 1.1865 0.0678 0.85 234 -0.9593 0.5773 0.0651 0.85 246 -0.2261 0.8455 0.0329