CLAS physics database search results Measurement E151M1625 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 138 -2.0438 0.9528 0.1226 0.65 222 -1.0018 1.0442 0.0655 0.75 222 -1.3458 0.8946 0.0838 0.75 234 0.6733 1.0367 0.0493 0.55 222 -0.9212 0.8797 0.0628 0.65 138 -0.2233 0.8991 0.0329 0.65 222 0.1987 0.8986 0.0323 0.75 222 -1.1036 0.7978 0.0726 0.85 126 0.9553 0.8881 0.0646 0.85 222 0.5208 0.8904 0.0433