CLAS physics database search results Measurement E151M1417 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.35 54 0.7933 0.8093 0.0944 0.55 246 -1.2102 0.7602 0.1398 0.65 234 -0.8585 0.8026 0.1014 0.65 246 -0.2878 0.5696 0.0442 0.65 258 -1.347 0.5528 0.1549 0.75 246 0.1612 0.7917 0.0351 0.75 258 -0.7412 0.6378 0.0888 0.85 246 0.2138 0.7761 0.0385 0.85 258 0.5236 0.6363 0.0662 0.85 270 1.6211 0.7826 0.1853