-- AlexanderFedotov - 24-Nov-2009

Average and Peak ET
of probe jet vs iEta

1. Intro

It was found in the Hcal Dijet Logbook page 1 ( Sec.4.2.1 ) from the ET_peak / Pthat_threshold for tag jets in 2009 sample (PThat > 30) that the the uncorrected tag jet energy is underestimated by factor ~2. And the "unbiased" HF correction was found to be 0.50 (Sec.5.5). => It looks like the jet energy scale in HF is roughly correct.

Puprose of this study: try to see the jet scale recovery for probe jets as going from barrel region to HF, by looking at the evolution of the ET(probe jet) distribution.

Input sample: 2009 PThat>30, 10 TeV Version 1 , one root file QCD_Pt30_10TeV.hi_100.root with 70946 evs

Plots were made interactively with the script .

2. Probe jet only

The < ET > vs iEta plot:


Original size: gif , eps

  • ET growth in HF as |iEta| increases, stops at |iEta| ~34, and changes to a fall off. This must be a reflection of boudary condition E(true probe jet) < E(beam), thus only the lowest values of ET(probe) get allowed in this region. For the same reason, a third jet contribution may become more important near this boundary.

The ET distributions are shown below for 7 bins in |iEta|. The peak positions as found by the standard root peak finder (function ShowPeaks ) are marked with red triangles.


Original size: gif , eps

The ET peak values from the above plots are tabulated below:

iEta range Peak ET / GeV peak(1-9) /
peak(iEta)
1-9 14.5 1.000
10-16 13.5 1.074
17-19 12.4 1.169
20-25 16.4 0.884
26-29 19.2 0.755
30-35 23.1 0.628
36-40 24.1 0.602

  • we do not get .50 , rather .60 only
  • are numerous cutoffs applied in the calibrtion, important? May well be...

3. Selecting η(tag) < 1 . Zooming HF region. Use tag jet directly for a probe in HF.

Now we add cutoff η(tag jet) < 1, used in calibration normally.

Probe jet ET :


Original size: gif , eps

  • In HF region, the average ET is only few percent bigger than on the plot w/o η cutoff . This seems to be insignificant.

Tag jet ET but still vs probe jet iEta:


Original size: gif , eps

  • The average ET( tag jet) in HF region (~20 GeV) is ~10% lower than ET( probe ) on the very first plot ( ~22 GeV at |iEta| <=12 ) .
  • What about the shape of the ET(tag) distribution relative to the ET(probe) one:
    • does it shrink?
    • does the peak value move?

Let us see:


Original size: gif , eps

Peak values are collected in the table:

iEta range Peak ET(tag) / GeV Peak ET(probe) / GeV peak_tag /
peak_probe
31-35 15.3 24.1 0.635
36-40 14.4 24.3 0.593

  • Nothing good! We still get ~0.6 but not 0.5
  • Peak method seems to be quite imprecise.
  • Other cuts may be much more important than η < 1 ( e.g. ET(third jet) < 5 is a very stong one!)


Topic attachments
I Attachment History Action Size Date Who Comment
Unknown file formateps ProbeJet.ET_in_iEta_bins.eps r1 manage 52.6 K 2009-11-24 - 21:00 AlexanderFedotov  
GIFgif ProbeJet.ET_in_iEta_bins.gif r1 manage 40.5 K 2009-11-24 - 20:54 AlexanderFedotov  
Unknown file formateps ProbeJet.Mean_ET_vs_iEta.eps r1 manage 19.0 K 2009-11-24 - 20:54 AlexanderFedotov  
GIFgif ProbeJet.Mean_ET_vs_iEta.gif r1 manage 13.3 K 2009-11-24 - 20:53 AlexanderFedotov  
Unknown file formateps ProbeJet_ET_vs_iEta_at_etaTag_lt_1.eps r1 manage 19.3 K 2009-11-25 - 04:34 AlexanderFedotov  
GIFgif ProbeJet_ET_vs_iEta_at_etaTag_lt_1.gif r1 manage 15.4 K 2009-11-25 - 04:34 AlexanderFedotov  
Unknown file formateps TagJet_ET_vs_ProbeJet_iEta_at_etaTag_lt_1.eps r1 manage 18.7 K 2009-11-25 - 04:37 AlexanderFedotov  
GIFgif TagJet_ET_vs_ProbeJet_iEta_at_etaTag_lt_1.gif r1 manage 15.3 K 2009-11-25 - 04:35 AlexanderFedotov  
Unknown file formateps etaTag_lt_1.Tag_And_Probe_ET_in_HF_bins.eps r1 manage 32.3 K 2009-11-25 - 06:35 AlexanderFedotov  
GIFgif etaTag_lt_1.Tag_And_Probe_ET_in_HF_bins.gif r1 manage 37.4 K 2009-11-25 - 06:33 AlexanderFedotov  
C source code filec rd_tree2.C r1 manage 7.8 K 2009-11-25 - 06:32 AlexanderFedotov  
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Topic revision: r6 - 2009-12-04 - AlexanderFedotov
 
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