CLAS physics database search results Measurement E151M1828 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 126 0.9244 0.8962 0.0635 0.65 258 0.6103 0.7818 0.0476 0.75 102 1.2 0.8275 0.0787 0.75 246 -1.4941 0.6441 0.0954 0.85 66 0.4203 0.835 0.0394 0.85 270 1.2097 0.6981 0.0792 0.95 258 0.7338 0.6797 0.0536