CLAS physics database search results Measurement E151M144 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.45 54 -0.8459 0.7999 0.1008 0.45 66 2.5738 0.8497 0.2944 0.55 54 0.4829 0.8223 0.0626 0.55 234 0.5807 0.7752 0.0726 0.65 42 -1.0402 0.7185 0.1221 0.65 222 0.2711 0.7201 0.043 0.65 234 -1.0459 0.6364 0.1227 0.65 246 -1.1649 0.5189 0.1359 0.75 234 0.502 0.6903 0.0645 0.85 222 1.4956 0.7529 0.1728 0.85 234 0.1204 0.6894 0.033