CLAS physics database search results Measurement E151M381 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.65 126 -1.0662 0.6261 0.0725 0.75 258 0.1664 0.6709 0.0317 0.95 270 0.4922 0.5436 0.0428 0.65 234 1.7009 1.3585 0.1067 0.75 258 0.2517 0.942 0.0336 0.85 246 -0.0515 0.9134 0.0302 0.85 258 3.3641 3.3641 0.2048 0.95 258 1.4188 1.098 0.0906