CLAS physics database search results Measurement E151M2428 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 270 -0.0407 1.0683 0.0301 0.85 102 -1.3159 0.8458 0.1 0.85 114 0.3075 0.9868 0.0374 0.85 186 -0.3193 0.9854 0.0379 0.85 198 -1.9731 0.9004 0.1462 0.85 210 -0.6043 0.9715 0.0531 0.85 222 -2.0098 0.8319 0.1488