CLAS physics database search results Measurement E151M1241 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.35 294 -0.3133 0.6059 0.0464 0.45 282 -0.2054 0.4991 0.0379 0.45 294 0.0663 0.5435 0.0309 0.55 270 -0.4317 0.5211 0.0572 0.55 282 0.7188 0.4494 0.0864 0.65 270 -0.1961 0.5007 0.0373 0.65 282 -0.012 0.5902 0.03 0.85 126 0.2075 0.6267 0.0381