CLAS physics database search results Measurement E151M1959 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 282 -1.1898 2.2325 0.1134 0.85 90 0.5185 3.0913 0.0563 0.55 282 -0.0726 0.4592 0.0304 0.65 270 -0.5163 0.4745 0.045 0.65 294 0.8082 0.4911 0.0605 0.75 282 0.5009 0.4323 0.0443 0.75 294 -0.542 0.473 0.0463 0.85 90 0.0076 0.5682 0.03 0.85 102 -0.413 0.556 0.0403 0.85 282 -0.0679 0.5191 0.0303 0.95 102 -1.0785 0.794 0.0763 0.95 114 0.4667 0.8651 0.0427 0.95 126 0.3361 0.8246 0.0371