CLAS physics database search results Measurement E151M4 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.55 258 -0.1061 0.4103 0.0323 0.55 270 0.8034 0.4374 0.0962 0.65 246 -0.0132 0.4613 0.03 0.65 258 0.1563 0.3403 0.0349 0.65 270 -0.045 0.3688 0.0304 0.75 162 0.259 0.5367 0.042 0.75 174 0.1849 0.5297 0.0366 0.75 186 -0.0636 0.4336 0.0309 0.75 198 -0.1488 0.4425 0.0344 0.75 210 -0.5339 0.4197 0.0677 0.75 222 -0.1241 0.451 0.0332 0.75 234 0.6638 0.5272 0.0813 0.75 258 -0.1127 0.3755 0.0326 0.85 174 0.2317 0.4508 0.0399 0.85 198 0.0269 0.4254 0.0302