First Look at Charged Pion Trigger Bias

The charged pion A_LL analysis selects pions from events triggered by the EMC. This analysis attempts to estimate the systematic bias introduced by that selection.


  • Simulation files, database timestamps, and selection cuts are the same as the ones used in the 2005 Charged Pion Data / Simulation Comparison
  • Polarized PDFs are incorporated into simulation via the framework used by the jet group. In particular, only GRSV-std is used as input, since LO versions of the other scenarios were not available at the time.
  • Errors on A_LL are calculated according to Jim Sowinski's recipe.


The BBC trigger has a negligible effect on the asymmetries, affirming its use as a "minimum-bias" trigger. The EMC triggers introduce a positive bias of as much as 1.0% in both asymmetries. The positive bias is more consistent in JP2; the HT2 asymmetries are all over the map.