The purpose of these histograms is the continuation of Justin's presentation entitled Run 11 Beam Background Study.  The source of background being tested for by this analysis is 'spray' from one or both of the beams before they enter the detector.  If this is where the background is coming from there should be a correlation between the number of hits in the endcap and barrel when a trigger condition is satisfied.

The histograms that follow look specifically at W triggers in the endcap and the barrel both for hits where there was no distinction made between having a reconstructed vertex or not, and hits where there was no vertex reconstructed.  They use data from five consecutive runs (12051006-12051010).

The histograms that follow are for L2BW triggers.  On the left are hits where no distinction was made between having a reconstructed vertex or not; on the right are hits that had no vertex.  From top to bottom the plots below are for 7-bit bXing = [0,30] , [31,39] , [40,110] , [111,119].

As can be seen in the preceding plots, all hits (with the exception of one event in the first abort gap) that occurred during the abort gaps did not have a reconstructed vertex.  Also, the hits that did not occur during an abort gap and did not have a reconstructed vertex are located in the densely populated region between 0 and 30 on the x-axis and lie on the x-axis.  This suggests that there is not a strong correlation between hits in the endcap and hits in the barrel and, thus, that the background is not coming from part of the beam 'spraying off' prior to entry into the detector.

Similar results can be seen in the histograms for L2EW triggers. The layout for the plots of L2EW triggers is similar to that of L2BW triggers.