CLAS physics database search results Measurement E151M2304 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 90 0.7863 0.9922 0.0644 0.65 102 0.612 0.9277 0.0536 0.75 54 0.4128 0.9655 0.0424 0.75 102 0.0029 1.0762 0.03 0.75 270 -1.4216 0.8567 0.1074 0.85 102 0.4084 0.9988 0.0422 0.85 210 0.1718 1.064 0.0325 0.85 234 1.1623 0.8765 0.0895 0.85 270 -0.8706 0.8419 0.0699 0.95 294 -1.2284 0.7082 0.094 0.95 306 0.3193 0.6969 0.0379 0.95 318 1.1159 0.8472 0.0863