what if there are HLT jets but no rec jets?

In the calculation of the trigger efficiency, there may be cases when an HLT exists but no there is no rec jet that corresponds to it. One reason for this could be when the online HLT system reconstructs jets from noise or pile-up. These would later be discarded from the offline reconstruction, which in any case is more precise.

This is actually observed in the dataset. When checking the data file with TTree::Sacn() after applyJEScorrecion, one gets a list of such cases.

events->Scan("@recJets.size():@hltJets.size()", "@recJets.size() == 0 && @hltJets.size() > 0");
************************************
*    Row   * @recJets. * @hltJets. *
************************************
*     6164 *         0 *         1 *
*     6778 *         0 *         1 *
*     6788 *         0 *         1 *
*     7043 *         0 *         1 *
*     7047 *         0 *         1 *
*     7049 *         0 *         1 *
*     7100 *         0 *         1 *
.........

The dots indicate that the list goes on for many events, but was cut short to save space.

This issue is a fololow-up on the discussion in MR !240 (merged) .