CLAS physics database search results Measurement E151M710 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.55 258 0.0109 0.7122 0.03 0.65 198 0.3426 0.7545 0.0366 0.75 258 0.5664 0.7563 0.0458 0.75 270 0.2317 0.6734 0.0332 0.75 282 -0.0358 0.6147 0.0301 0.85 138 0.3974 0.7426 0.0386 0.85 210 -0.5848 0.6198 0.0467