CLAS physics database search results Measurement E151M3412 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.45 282 -0.3209 0.272 0.0307 0.65 282 0.3767 0.2352 0.0309 0.75 258 -0.2418 0.2847 0.0304 0.75 270 0.2348 0.2686 0.0304 0.75 306 0.114 0.2783 0.0301 0.95 282 -0.004 0.2715 0.03