# Presentation: 078078

## Improving Jet Resolutions

- Motivation
- Physics Effects
- Definitions of Resolution
- Optimum Use of All        Detector Information
- Testing New Algorithms       With Collider Data
- Last few months...

## Motivation

-  Improve mass resolutions
-  Sharpen Jet and Missing Et cuts
-  Use the extended tracking of the Run II detectors
-  Reduce pileup effects

- SHW Result

## Physics Effects

- Large-Angle Final State      Gluon Radiation
- Initial State Gluon Radiation
- Underlying Event Fluctuations
- Neutrinos from                   Heavy Quark Decays

## Main Physics Effect is Due to Final State Gluon Radiation

## Comparison of Pure Physics Effects and Pure Detector Effects

- Cone 1.0

## Strategies to Handle    Gluon Radiation          (other than extra jet cuts)

- Optimized Cone Size
- Kt vs Cone Algorithm
- Optimized Merging Criteria    of Cone Jets
- Not Even Easy to Define       the Best Answer

## Definitions of Resolution

- W  Mass (GeV)

## Full Signal to Background Study Says Merging Within Radius 1.0 Best  

## Optimum Use of        Detector Information

- Run I jets measured with  calorimeters only
- Average track pt in a 50 GeV jet is    4 GeV (eg. from a 115 GeV Higgs)
- Tracking resolution for 4 GeV     track  is about 0.5%,  while calorimeter resolution is 30%.
- Monte Carlo says potential x3(!) improvement with perfect ID

## Optimum Use of        Detector Information

- Using tracks allows the possibility of reducing jet pileup from other collisions by x3
- Preshower detectors used in ZEUS give 17% improvement (talk by Magill at CALOR2000)
- Shower Maximum detectors useful in tagging photons in jet

## Optimum Use of        Detector Information

- _Many other possibilities:_
-    muon hits for leakage estimate
-  soft lepton and vertex information for b jets
- phototube ratios
- crack chambers
- ...

## New CDF Algorithm Using Tracking, Calorimeter, and Shower Maximum Detectors 

- New CDF Algorithm Using Tracking, Calorimeter, and Shower Maximum Detectors

## Slide 13

## Photon+Jet Events (25-30 GeV)

- Pt  (GeV)

- Pt  (GeV)

- Pt  (GeV)

- Pt  (GeV)

- Cal Only

- Cal Only

- Cal+Tracking

- Cal+Tracking

- Photon+Jet Events (25-30 GeV)

## Jet Resolution and Energy Scale Comparison

## Dijet Mass Resolution Group

- Work shown so far mostly Pisa+Rockefeller                                 (Stefano Lami, Andrea Bocci, Giuseppe Latino,         Davide Costanzo, Riccardo Paoletti ...)
- Documented in CDF4259(gluon radiation), CDF5507,5416,5179,4681, Bocci thesis (tracking+calorimeter+shower max algorithm)
- Group meets Off-Week Fridays at 9am    in the Pump Room + Video

## Dijet Mass Resolution Group

- Many more studies underway,                          but still much to do.
- Everything so far is with ||<0.7,  need someone to start developing tools for the ENDPLUG
- Many differences compared to central,  ISL tracking, scintillator shower max,    u/v shower max segmentation,          tower-based scintillator preshower...

## Future Products

- Ultimate goal could be a list of  4-vectors,  sometimes more    than 1 per tower...

- ±

- 

## Last few months...

- Stefano Lami finished CDF5690,     detailed comparison of data with                             PYTHIA 6.115 + Run I Simulation           of Photon+Jet

## Last few months...

- Beate Heinemann of Liverpool and the Rome group led by Subir Sarkar           have joined the study.
- Detailed Run II Monte Carlo                study of  Zqqbar begun.                  Meant to catalog and fix algorithm mistakes, and find the ultimate    limitations to jet resolutions.

## Last few months...

- Beate Heinemann:  Use track if E/P<1,  otherwise use calorimeter.  About 20% improvement.