CLAS physics database search results Measurement E151M968 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.45 282 0.1609 0.7002 0.0322 0.65 282 1.1346 0.7973 0.0882 0.75 258 -0.3544 0.6456 0.0396 0.75 270 0.7202 0.7761 0.0606 0.75 306 0.0608 0.6756 0.0303 0.95 282 0.931 0.6873 0.0744