CLAS physics database search results Measurement E151M2380 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.85 78 0.1454 1.0145 0.0318 0.85 210 0.0471 1.1654 0.0302 0.95 222 0.5202 0.8151 0.0482 0.95 234 -0.3368 0.881 0.0387 0.95 246 1.6354 0.8535 0.1223 0.95 258 0.0014 0.8593 0.03 0.95 270 -0.1889 0.9644 0.033