CLAS physics database search results Measurement E151M2268 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 90 -0.0804 0.914 0.0306 0.65 114 0.6722 0.8473 0.0572 0.65 234 1.6722 0.9123 0.1249 0.75 102 1.6197 0.9622 0.1212 0.75 258 -0.1798 0.8926 0.0327 0.75 282 2.6819 2.6819 0.1968 0.85 246 -0.7878 0.7578 0.0645 0.85 294 0.718 0.6507 0.0601 0.85 306 0.3541 0.8151 0.0395 0.95 282 -1.5485 0.6808 0.1162