Inclusive Jet Production Cross Section using the KT Algorithm at CDF Run II Blessing Talk

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Inclusive Jet Production Cross Sectionusing the
KT Algorithm at CDF Run IIBlessing Talk CDF
Note 7576

• R. Lefèvre, M. Martinez, O. Norniella
• QCD Meeting, April 22nd 2005

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Summary

• Cosmic background found
• 2 cosmic backgrounds over 86 highest PT jet
  events
• Change Missing ET significance cut
• Less loose cut
• Also applied using leading jet PT (Ken comment)
• Selection event by event now, before was in fact
  jet by jet
• The highest PT jet disappeared
• Change the last bins 527-607-800 becomes 527-700
• Redo the whole analysis
• Nothing change conceptually apart from the
  Missing ET significance cut
• Check that there is no more cosmic background
• The note has been updated this morning
• Also investigate a less tight cut on additional
  jets for what concerns the Dijet Balance and the
  Bisector Method
• Results very similar

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1st cosmic event
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2nd cosmic event
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TDC , EM Fraction, ? PT Tracks
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Missing ET significance new cut
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No more cosmic background?

• Check Missing ET significance distribution is
  more details
• For each datasets as before
• For leading jet PT gt 50, 75, 100, 150, 250, 350
• Check EM fraction
• For leading jet PT gt 50, 75, 100, 150, 250, 350

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Missing ET significance (1/2)
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Missing ET significance (2/2)
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EM Fraction
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Data samples / Event selection

• Framework
• Version 5.3.3nt of the code latest primary
  vertex finder algorithm
• Jet datasets xxxx0d latest calorimeter
  calibration (13A)
• Version 5.3.3 of the Monte-Carlo
• Pythia Tune A taken as nominal MC, Herwig only
  considered for systematics
• Run selection
• Version 7 of QCD good run list (no Silicon
  requirement)
• Run 155368, 155742 excluded discard 3.8 pb-1
• Cross section dropped of about 40
• Integrated luminosity 385 pb-1 (1.019 corrective
  factor take into account)
• Event selection
• Jets defined with the KT algorithm D 0.5, 0.7
  or 1.0
• At least one jet with 0.1 lt YJETlt0.7 and
  PTRAW ? 10 GeV/c
• At least one primary vertex of Quality ?12, best
  primary vertex Vz lt 60 cm

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Trigger study
Trigger efficiency gt 99 raw PT in GeV/c
Dataset D 0.5 / 0.7 / 1.0
STW5 24 / 30 / 34
JET20 25 / 33 / 40
JET50 56 / 58 / 72
JET70 78 / 80 / 92
JET100 112 / 114 / 128
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MC simulation

• CDF simulation
• Tracks E / p reasonably well reproducedfor
  central calorimeters
• Pythia Tune A used as nominal MC
• Includes tuned parametersfor the Underlying
  Event
• Reproduces the Jet Shapes
• Outlook
• Data / MC comparison of raw variables
• Dijet Balance
• Bisector Method
• Additional requirement
• 1 and only 1 primary vertex of Quality ?12

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Dijet Balance method

• Event selection
• 2 and only 2 jets with PTRAW ? 10 GeV/c
• One jet (trigger jet) with 0.2 lt ?DTRIG lt 0.6
• The other jet (probe jet) with 0.1 lt YJETlt0.7
• 1 and only 1 primary vertex of Quality ?12 ,
  Vz lt 60 cm
• Missing ET significance criterion (applied to
  leading jet)
• Definitions
• PTMEAN (PTPROB PTTRIG) / 2
• ?PTF (PTPROB - PTTRIG) / PTMEAN
• In bin of PTMEAN
• ? (2 lt?PTFgt) / (2 - lt?PTFgt)
• Event by event ? PTPROB / PTTRIG

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Dijet Balance results
2 and only 2 jets PTMIN 15 GeV/c
2 and only 2 jets PTMIN 10 GeV/c
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Bisector Method

• Event selection
• 2 and only 2 jets with PTRAW ? 10 GeV/c
• The 2 jets with 0.1 lt YJETlt0.7
• 1 and only 1 primary vertex of Quality ?12 ,
  Vz lt 60 cm
• Missing ET significance criterion (applied to
  leading jet)
• Definitions
• PTMEAN (PTRAW1 PTRAW2) / 2
• ? (?JET1 - ?JET2) / 2
• ?PT// (PTRAW1 PTRAW2) cos(?)
• ?PTPERP (PTRAW1 - PTRAW2) sin(?)
• In bin of PTMEAN
• ?// rms of ?PT// distribution
• ?PERP rms of ?PTPERP distribution
• ?D ? (?2PERP - ?2//) / ? 2

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Bisector Method results
2 and only 2 jets PTMIN 15 GeV/c
2 and only 2 jets PTMIN 10 GeV/c
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Pile-Up Correction method

• Correction
• PTRAW (Pile-Up Corrected) PTRAW ?D ? (NVQ12
  1)
• ?D extracted from the data
• Shapes of normalized cross sections vs PTRAW
  (Pile-Up Corrected) dividing the data in 2
  sub-samples of instantaneous luminosity
• High Luminosity / Low Luminosity
• Low Luminosity 5 to 15 ? 1030 cm-2s-1
• High Luminosity gt 35 ? 1030 cm-2s-1

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Pile-Up Correction results
D ?D GeV/c
0.5 1.06 (0.35 / -0.24)
0.7 1.62 (0.70 / -0.46)
1.0 2.84 (1.42 / -0.47)
Compatible results obtained using other high
luminosity sub-samples
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Pile-Up Correction MC check method

• Ratio of cross sections vs PTRAW (Pile-Up
  Corrected) as obtained with 1 pile-up MC and no
  pile-up MC
• 1 Pile-Up MC / No Pile-Up MC

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Pile-Up Correction MC check results
Results compatible with the one obtained from the
data
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Absolute correction

• Method
• KT algorithm run at calorimeter and hadron level
• Pair of calorimeter-hadron jets matched in the
  Y- ? space
• ?R ? (?Y2 ??2) lt D
• Closest hadron jet if more than one within ?R
  requirement
• ltPTHAD PTRAWgt vs ltPTRAWgt
• Fit by a 4th order polynomial
• Average computed in (PTHAD PTRAW) / 2 bins

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Unfolding

• MC
• Jets at hadron level
• No cut but YJET applied on hadron level jets
• NiHAD
• Jets at calorimeter level
• All cuts applied, use PTCOR
• NiCAL
• Bin-by-bin unfolding factor Ci NiHAD / NiCAL
• Data using PTCOR
• NiDATA UNFOLDED Ci ? NiDATA NOT UNFOLDED
• MC weighted so that it reproduces the shape of
  the jet PT spectrum
• Relative difference between unfolding coming from
  non weighted and weighted MC took as a systematic

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Systematic uncertainties (1/2)
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Systematic uncertainties (2/2)
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UE / Hadronization correction
?

?
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CHAD vs D

• Correction limited to PTJET gt 54 GeV/c

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NLO

• JETRAD CTEQ61 package
• ?R ?F Maximum Jet PT / 2
• K-factor (NLO / LO) 1 for 70GeV/c
  hep-ph/0303013
• NLO uncertainties
• Scale ?R ?F Maximum Jet PT
• Symmetric uncertainties
• PDF
• Asymmetric uncertainties
• Dominates by gluon at high-x contribution
• PDF uncertainties dominate
• NLO corrected to hadron level multiplying the
  prediction by CHAD

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Results
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Event Display highest PTJET event
Raw Jet Et 533 GeV
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An interesting event