As I detail in the previous blog post, I impose two track based cuts on the jets I consider in my analysis. I require that jets have:

• Jet RT <= 0.94
• Jet Sum Track Pt >= 0.5

These cuts are important for reducing the pile-up background in the inclusive jet analysis. Requiring that we see two back to back jets in an event as is done in the dijet analysis should eliminate much of the pile-up background and thus weaken the need for the above cuts. More importantly, as we extend the analysis into the endcap where tracking is falling off, the above cuts will start to remove more and more valid jets.

To investigate the affect that the above cuts have on the jets seen in my analysis I have run two samples of 50 runs. One has the standard configuration where the above cuts are applied to all jets. The second applies the above cuts to jets in the barrel (jet detector eta must be less than 1.0) and not the endcap. The samples are identical in all other respects.

Figure 1: This figure shows the dijet mass spectrum for the total, barrel - barrel, east barrel - endcap, west barrel - endcap, and endcap - endcap acceptances. The red curve is the spectrum when the above cuts are applied to all jets. The blue curve is the spectrum when the above cuts are applied only to jets which land in the barrel.

 Figure 2: This figure shows the eta spectra for the high pt jet (top left) and low pt jet (top right) in the dijet. Again the red curve shows the spectra when the above cuts are applied to all jets and the blue curve shows the spectra when the cuts are applied only to barrel jets. The bottom pannels show the ratio of the blue curve to the red curve.

Conclusions: In figure 1 we see that the biggest discrepancies between the two sets occurs when one of the jets is in the endcap as we would expect. In figure 2 we see that although we get more jets at high eta with the barrel only cuts, there is still a number enhancement over all etas. This is because adding jets in the endcap will allow more barrel - endcap coincidences. We also see that the eta spectrum enhancement is more pronounced at high eta in the low pt jet sample than in the high pt jet sample.

More study will be needed to see how much background in admitted with relaxing these cuts. It may even be possible to relax these cuts in the barrel as well if the dijet condition itself is good enough at rejecting pile-up.