CLAS physics database search results Measurement E151M1605 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 126 -1.2127 1.0233 0.0766 0.65 246 0.6715 1.0319 0.0492 0.75 234 0.2542 1.0349 0.0334 0.75 258 1.3348 0.9175 0.0832 0.85 258 0.1895 1.0599 0.032 0.55 246 -0.5629 0.9273 0.0451 0.85 270 1.4632 0.8107 0.0927 0.95 102 -0.1628 0.8094 0.0315