CLAS physics database search results Measurement E151M1708 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 90 0.8738 0.6119 0.0609 0.65 258 1.2866 0.6707 0.0835 0.75 246 -1.1063 0.4916 0.0734 0.75 258 0.6514 0.5771 0.0496 0.75 270 0.4516 0.6616 0.0406 0.85 126 -0.2318 0.6809 0.0331 0.85 138 0.6178 0.637 0.048 0.85 162 -0.9416 0.6265 0.0645 0.85 246 -1.1083 0.5522 0.0736