CLAS physics database search results Measurement E151M1667 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 210 -0.8823 1.1853 0.0594 0.65 222 -0.8248 1.1854 0.0566 0.75 222 0.076 1.1032 0.0303 0.75 234 0.141 1.0738 0.0311 0.85 222 -1.9931 0.7987 0.1197 0.85 234 -0.5949 1.1694 0.0458 0.85 246 0.2198 0.9576 0.0326 0.65 234 -0.8595 0.8263 0.0596 0.75 234 -2.101 0.764 0.1294 0.85 222 0.2888 0.8259 0.0346 0.85 234 -0.4614 0.7889 0.0408