CLAS physics database search results Measurement E151M1492 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 138 -1.0391 1.0115 0.0675 0.75 246 2.1186 2.1186 0.1268 0.85 102 0.4313 0.9886 0.0391 0.85 114 1.2223 1.3969 0.0771 0.85 282 -0.4001 0.9276 0.038 0.65 294 1.0188 0.804 0.068 0.85 102 0.0962 0.7254 0.0305 0.85 126 0.4741 0.7446 0.0413 0.85 162 0.0201 0.7678 0.03 0.85 270 -0.0689 0.7261 0.0303 0.85 294 0.2607 0.7924 0.0338