CLAS physics database search results Measurement E151M1926 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.45 270 -0.3872 0.7167 0.0381 0.55 270 -0.142 0.6872 0.0312 0.65 138 -1.4629 0.5892 0.0936 0.75 210 1.1967 0.6639 0.0785 0.75 222 0.1331 0.7109 0.0311 0.75 282 -0.0405 0.7014 0.0301 0.85 102 -0.0358 0.6665 0.0301 0.85 198 -1.0868 0.6776 0.0724 0.85 234 -0.8309 0.6141 0.0586 0.85 246 -0.5549 0.6807 0.0451 0.95 234 -0.9538 0.5964 0.0651