# Presentation: 022438

## Inclusive Jet Production Cross Sectionusing the KT Algorithm at CDF Run IIBlessing Talk – CDF Note 7576 

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

## 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

## 1st cosmic event

## 2nd cosmic event

## TDC , EM Fraction,  PT Tracks

## Missing ET significance ... new cut

## No more cosmic background? 

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

## Missing ET significance (1/2)

## Missing ET significance (2/2)

## EM Fraction

## 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 < |YJET|<0.7  and   PTRAW  10 GeV/c
- At least one primary vertex of  Quality 12, best primary vertex |Vz| < 60 cm

## Trigger study

| 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 |

- Trigger efficiency > 99 % [raw PT in GeV/c]

## 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

## Dijet Balance: method

- Event selection
- 2 and only 2 jets with  PTRAW  10 GeV/c
- One jet (trigger jet) with  0.2 < DTRIG < 0.6
- The other jet (probe jet) with  0.1 < |YJET|<0.7
- 1 and only 1 primary vertex of  Quality 12 ,  |Vz| < 60 cm
- Missing ET significance criterion (applied to leading jet)
- Definitions
- PTMEAN = (PTPROB + PTTRIG) / 2
- PTF = (PTPROB - PTTRIG) / PTMEAN
- In bin of  PTMEAN
-  = (2 + <PTF>) / (2 - <PTF>)
- Event by event   = PTPROB / PTTRIG

## Dijet Balance: results

- 2 and only 2 jets
- PTMIN = 10 GeV/c

- 2 and only 2 jets
- PTMIN = 15 GeV/c

## Bisector Method

- Event selection
- 2 and only 2 jets with  PTRAW  10 GeV/c
- The 2 jets with  0.1 < |YJET|<0.7
- 1 and only 1 primary vertex of  Quality 12 ,  |Vz| < 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

## Bisector Method: results

- 2 and only 2 jets
- PTMIN = 10 GeV/c

- 2 and only 2 jets
- PTMIN = 15 GeV/c

## 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: > 35  1030 cm-2s-1

## 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

## 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

## Pile-Up Correction: MC check results

- Results compatible with the one obtained from the data

## Absolute correction

- Method
- KT algorithm run at calorimeter and hadron level
- Pair of calorimeter-hadron jets matched in the  Y-   space
- R =  (Y2 + 2) < D
- Closest hadron jet if more than one within R requirement
- <PTHAD – PTRAW> vs <PTRAW>
- Fit by a 4th order polynomial
- Average computed in (PTHAD + PTRAW) / 2  bins

## 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

## Systematic uncertainties (1/2)

## Systematic uncertainties (2/2)

## UE / Hadronization correction

**=**

****

****

## CHAD vs D

- Correction limited to PTJET > 54 GeV/c

## 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

## Results

## Event Display: highest PTJET event

**Raw Jet Et = 533 GeV**

## An interesting event