# Presentation: 740393

## Outline
     Motivation
Inclusive jet cross section
Dijet mass
Jet shapes
     Summary

_*Outline*_
**     ****Motivation**
**Inclusive jet cross section**
**Dijet mass**
**Jet shapes**
**     ****Summary**

**Rob Snihur**
**University College London**
***for the CDF collaboration***

***La Thuile******Fri. Mar. 14, 2003***

- Jet studies at CDF in Run II

## Motivation

**Tevatron = jet factory**
**Probe highest energy scales**
**Higher **√***s***** ******** higher *****σ***** (factor 3 for *****E******T***** > 500 GeV)**
**Already more jets than in Run I**
**Test fixed-order QCD**
**look for deviations ******** new physics**
**Constrain PDFs**
**Analyses:**
**Inclusive jet cross section (counting jets)**
**Dijet Mass (bump hunting)**
**Jet Shapes & Energy Flow**

## Collider Detector at Fermilab (CDF)
 New plug calorimeter (1.1 < | | < 3.6)
 New tracking system
 Upgraded trigger

** ****New plug calorimeter (1.1 < |********** ****| < 3.6)**
** ****New tracking system**
** ****Upgraded trigger**

**Upgraded Tevatron at Fermilab****√****s = 1.8 TeV ******** 1.96 TeV**
**Higher ****σ****(****jet)**

- Tevatron & CDF

**σ****(jet) ratio:   Run II / Run I**

**jet *****E******T***** (GeV)**

**NLO QCD**

## Highest Energy Jets in Run II

**Run 152507 Event 1222318**
**Dijet Mass = 1364 GeV (corr)**

_**Jet 2**_
***E******T***** = 546 GeV (raw)**
*********det***** = -0.30**

**CDF Run II Preliminary**

_**Jet 1**_
***E******T***** = 583 GeV (raw)**
*********det***** = 0.31**

## Inclusive Jet Cross Section

**|*****z*****vertex****| < 60 cm**

- _Inclusive Jet Cross Section_

** **

**Repeat Run I analyses**
**Use CDF cone jet algorithm ****with R = 0.7 (JetClu)**

**∑**** *****E******T***** < 1500 GeV **

**Require fully efficient trigger**
**Apply jet energy corrections (same as in Run I)**

## Systematic Uncertainties

- Largest uncertainty

- Luminosity uncertainty = 6%

- Systematic Uncertainties

## Corrected: Log

** ****8 orders of magnitude!**
** ****Highest *****E******T***** jets ever!**

**CTEQ 6.1: hep-ph/0303013**

## Corrected: Linear

**Inclusive jet *****E******T***** (GeV)**

**Good agreement (within uncertainties)**

- CDF Run II Preliminary

**CDF data**

**5% Energy scale uncertainty**

**CTEQ 6.1 uncertainty**

**JetClu cone *****R***** = 0.7, ****√*****s***** = 1.96 TeV**

**σ**** ****ratio:   Data / CTEQ6.1**

## Run II & I

** ****Higher ****σ**** in Run II due to higher √*****s***
** ****Many uncertainties cancel in the ratio**

## Dijet Mass

- _Dijet Mass_

** ****Higher ****σ**** in Run II due to higher √*****s***
** ****3 more bins at high dijet mass!**

## Run II& I

**Consistent with inclusive jet cross section**

## Limits

## Jet Shapes

**ρ****(*****r*****)**

- _Jet Shapes_

**Differential jet shape definition**

***r***

**narrow**

**fat**

## Data & HERWIG

** ****Narrower jets at high *****E******T***** & low *****η***** **
** *****HERWIG***** agrees well with data**

- Data & *HERWIG*

- CDF Run II Preliminary

## Calorimeter vs. tracking

** ****Use COT tracks with *****p******T***** > 0.5 GeV**
** ****Agrees with calorimeter-based shape **
** ****Agrees with *****PYTHIA***

- CDF Run II Preliminary

## Energy flows

**Look *****outside***** the jet**
**Probe the underlying event**

## Energy flows

**Increasing ****Δη****jet**

**Increasing ****η****jet**

- CDF Run II Preliminary

## Summary

**CDF has preliminary measurements in Run II **
**Inclusive jet cross section**
**Dijet mass**
**Jet shapes & energy flow**
**Higher ****√****s ******** more jets at high *****E******T***
**Data samples w/ higher statistics than Run I**
**Dominant systematic: jet *****E*****-scale**
**General agreement w/ fixed-order QCD calculations & Monte Carlos**

## Outlook

**Reduced systematics**
**More data**
**Forward jets**

**Different jet algorithms**
**Other jet analyses**
**Dijet angular distribution**
**σ****(*****b*****-jet)**