CLAS physics database search results Measurement E151M1531 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 234 -0.0689 0.7628 0.0303 0.75 222 -1.1805 0.8442 0.0769 0.75 246 -0.5028 0.8558 0.0425