CLAS physics database search results Measurement E151M1707 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.25 66 -0.8327 0.5722 0.0587 0.45 282 0.2245 0.6472 0.0329 0.65 270 1.3176 0.523 0.0853 0.65 282 0.4756 0.616 0.0416 0.75 102 0.3677 0.6027 0.0374 0.75 258 -1.2993 0.5181 0.0843 0.75 282 0.8145 0.5724 0.0578 0.85 102 0.5749 0.5748 0.046 0.85 258 0.3593 0.613 0.0371