CLAS physics database search results Measurement E151M41 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.55 246 -0.6361 0.4802 0.0783 0.65 234 -0.3927 0.5588 0.0538 0.65 246 0.1892 0.4758 0.0369 0.65 258 -0.5337 0.4444 0.0677 0.65 270 -0.3139 0.5551 0.0466 0.75 246 0.6172 0.468 0.0764 0.75 258 0.1433 0.51 0.0341 0.85 246 0.6102 0.6099 0.0756