CLAS physics database search results Measurement E151M2049 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 90 3.2231 3.2231 0.2977 0.95 306 5.8042 3.1229 0.5343 0.65 114 0.2954 0.8277 0.0356 0.75 90 1.241 0.7218 0.0861 0.75 270 -1.3273 0.6862 0.0914 0.85 222 0.4757 0.9578 0.0431 0.85 234 0.1373 0.8648 0.0313 0.85 258 0.1081 0.8309 0.0308 0.85 282 0.0137 0.8401 0.03 0.95 294 0.0886 1.3043 0.0305