CLAS physics database search results Measurement E151M2102 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 126 0.2544 0.8496 0.0343 0.75 222 -0.3168 0.6668 0.0563 0.85 78 -0.3353 0.6257 0.0418 0.85 90 2.7222 0.8556 0.252 0.85 222 -0.6775 1.0215 0.0533 0.85 234 -0.6329 0.7097 0.0632 0.95 246 -1.7054 1.4727 0.1149 0.95 258 0.9937 1.4773 0.0713 0.95 282 0.495 2.1138 0.0545