CLAS physics database search results Measurement E151M1034 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.55 90 0.5104 0.8396 0.0479 0.75 270 -0.2915 0.7394 0.0368 0.75 282 0.6853 0.8413 0.0584 0.85 258 -0.1537 0.7417 0.032 0.85 270 -1.3972 0.5332 0.1064 0.85 294 0.1783 0.7234 0.0327 0.85 306 -0.1458 0.6419 0.0318 0.85 318 1.3298 0.78 0.1017 0.85 330 -0.177 0.6793 0.0327