Run 9 200GeV Dijet Data/Detector Level Simu Cut Order
There was a question raised about the jet eta / detector eta fiducial cut I place on my data ...
When creating dijets from the data and the detector level simulation, I place some fiducial eta cuts on the jets that I consider for further analysis. The relevant steps in the dijet selection process are below:
The question of my method concerns step 3 in which I restrict the range over which I will consider jets. The theory code will find the two highest pt jets at any rapidity. The worry then is that if the event has three or more jets and the highest pt jet is outside my fiducial region, I will select two lower pt jets at mid-rapidity.
I felt that cut 3 was appropriate at the data and detector level simulation level because it mitigated edge of detector effects (although I know the choice of limits is somewhat arbitrary). I will also point out that we place an effective eta cut no matter what because STAR is only instrumented over a finite eta range. If the highest pt jet was at an eta of -2.5, we would never detect it. NOTE: when doing the efficiency or trigger/reco bias corrections where I use the full pythia sample, I do not place any fiducial cuts on the jets I consider for the two highest pt jets.
To test the effect of cut 3, I compare the raw dijet yields from 9 runs using the dijet selection process outlined above (which is what is used in my current results) to the yields from the same 9 runs in which I have removed the fiducial cuts in step 3 leaving all other cuts the same. That is, I will select the two highest pt jets from the set of all jets STAR reconstructs, no matter what eta they are at. The comparison for each mass bin for the L2JetHigh and JP1 triggers are shown below.
Table 1: Raw L2JetHigh dijet yields for the original scheme with the fiducial eta cuts and the modified scheme with no eta cuts.
Table 2: Raw JP1 dijet yields for the original scheme with the fiducial eta cuts and the modified scheme with no eta cuts.
When creating dijets from the data and the detector level simulation, I place some fiducial eta cuts on the jets that I consider for further analysis. The relevant steps in the dijet selection process are below:
- Pick best vertex
- Ensure |z| <= 90 cm
- Select all jets in fiducal volume defined by: -0.8 <= eta <= 1.8 and -0.7 <= det eta <= 1.7
- Select two highest pt jets from step 3
- Make sure at least one jet from step 4 is triggered
- Rest of dijet cuts follow including cut which restricts jets to mid-rapidity ...
The question of my method concerns step 3 in which I restrict the range over which I will consider jets. The theory code will find the two highest pt jets at any rapidity. The worry then is that if the event has three or more jets and the highest pt jet is outside my fiducial region, I will select two lower pt jets at mid-rapidity.
I felt that cut 3 was appropriate at the data and detector level simulation level because it mitigated edge of detector effects (although I know the choice of limits is somewhat arbitrary). I will also point out that we place an effective eta cut no matter what because STAR is only instrumented over a finite eta range. If the highest pt jet was at an eta of -2.5, we would never detect it. NOTE: when doing the efficiency or trigger/reco bias corrections where I use the full pythia sample, I do not place any fiducial cuts on the jets I consider for the two highest pt jets.
To test the effect of cut 3, I compare the raw dijet yields from 9 runs using the dijet selection process outlined above (which is what is used in my current results) to the yields from the same 9 runs in which I have removed the fiducial cuts in step 3 leaving all other cuts the same. That is, I will select the two highest pt jets from the set of all jets STAR reconstructs, no matter what eta they are at. The comparison for each mass bin for the L2JetHigh and JP1 triggers are shown below.
Table 1: Raw L2JetHigh dijet yields for the original scheme with the fiducial eta cuts and the modified scheme with no eta cuts.
| Mass Bin | Original Yield | Modified Yield | (Orig-Mod)/Mod (%) |
| 16-19 | 11058 | 10936 | 1.12 |
| 19-23 | 18278 | 18124 | 0.85 |
| 23-28 | 14905 | 14820 | 0.57 |
| 28-34 | 8214 | 8175 | 0.48 |
| 34-41 | 3520 | 3515 | 0.14 |
| 41-49 | 1266 | 1266 | 0 |
| 49-58 | 383 | 383 | 0 |
| 58-69 | 139 | 139 | 0 |
| 69-82 | 22 | 22 | 0 |
| 82-100 | 5 | 5 | 0 |
Table 2: Raw JP1 dijet yields for the original scheme with the fiducial eta cuts and the modified scheme with no eta cuts.
| Mass Bin | Original Yield | Modified Yield | (Orig-Mod)/Mod (%) |
| 16-19 | 3365 | 3351 | 0.42 |
| 19-23 | 2304 | 2302 | 0.09 |
| 23-28 | 843 | 838 | 0.60 |
| 28-34 | 220 | 220 | 0 |
| 34-41 | 51 | 51 | 0 |
| 41-49 | 11 | 11 | 0 |
| 49-58 | 1 | 1 | 0 |
As can be seen from the tables, the limited sample I tested seems to indicate that the effect of changing cut 3 is quite small. So the question of exactly how dijets are chosen becomes one of consistency between the various dijet analyses.
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