CLAS physics database search results Measurement E151M1344 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 258 -0.1086 0.8144 0.0324 0.55 270 0.9222 0.9148 0.1082 0.65 246 1.4162 0.8592 0.1625 0.65 258 1.2594 0.8906 0.1452 0.65 270 -0.2429 0.9002 0.0406 0.75 138 0.5427 1.061 0.0682 0.75 258 -0.3516 0.7962 0.0497 0.75 270 0.2555 0.8565 0.0416 0.75 282 1.5689 0.7484 0.1795 0.85 126 0.4353 0.9238 0.0575 0.85 150 0.6945 0.8794 0.0839 0.85 246 1.1639 0.8228 0.1347 0.85 258 -0.8998 0.7199 0.1058 0.85 270 0.2944 0.7199 0.0447 0.85 282 -0.0883 0.6797 0.0316