First Jet Results using the Upgraded D0 Detector Nirmalya Parua (for the D0 Collaboration) State University of New York Stony Brook DPF 2002 College of William and Mary Williamsburg, Virginia, May 24-28, 2002

May 24-28, 2002 Nirmalya Parua

Jets

Jet is a collection of towers within a given cone R R   2    2  Where  is the azimuthal coordinate  is the pseudorapidity  = -ln tan(  /2) May 24-28, 2002 Nirmalya Parua

Calorimeter Overview

Y L. Ar in gap 2.3 mm

Drift time 430 ns    

Ur absorber Z Liquid argon sampling



X Stable, uniform response, rad. hard, fine spatial seg .

Cu pad readout on 0.5 mm G10 with resistive coat epoxy



LAr purity important ( impurity <0.5 ppm) Uranium absorber (Cu or Steel for coarse hadronic)



Compensating e/

 

1, dense



Uniform, hermetic with full coverage compact

 ||

< 4.2 (

 

Energy Resolution 2 o ),

l

int

> 7.2 (

total)



e:

s

E / E = 15% /



E + 0.3%



:

s

E / E = 45% /



E + 4% (as measured in Run I)

May 24-28, 2002 Nirmalya Parua

Jet Algorithms

   Cone Algorithm in Run I (1992-1995)     

Draw a cone of fixed size around a seed.

Compute jet axis by E T weighted mean and jet E T by summing over E T s.

Draw new cone around the new jet axis and recalculate axis and new E T.

Iterate Until stable.

Sensitive to soft radiation .

Improvements in RunII (2000 - ) Use 4 vector scheme instead of E T Add midpoints of jets as additional starting seeds.

Infrared safe

Nirmalya Parua May 24-28, 2002

Jets in Run I

Inclusive jet spectrum and Dijet mass spectrum measured in RunI well described by pQCD

May 24-28, 2002 Nirmalya Parua

Fermilab Accelerator Upgrade

Booster



p source CDF Chicago



Tevatron Main Injector (new)

May 24-28, 2002

DØ

 Two new machines at FNAL for Run II:  Main Injector 150 GeV conventional proton accelerator  Supports luminosity upgrade for the collider  Recycler  8 GeV permanent magnet (monoenergetic)  storage ring permits antiproton recycling from the collider  Nirmalya Parua Tevatron Status and Schedule  1.8 Tev  1.96 TeV  Goal:  L dt = 2 fb -1 in Run 2a 15 fb -1 + in Run 2b

3.56us

Bunch Structure

gap used to form trigger and sample baselines

Run I 6x6

superbunch 4.36us

gap 2.64us

396ns

Run II 36x36 Detector readout and trigger system upgrade must take into account smaller bunch crossing time Nirmalya Parua May 24-28, 2002

Jets in Run II

Cross section 2 times larger compared to Run I for jets with p T > 400 GeV Higher statistics will improve knowledge of proton structure at large x and searches for physics beyond the standard model (e.g. search for compositeness, W’, Z’ etc...) will be very exciting.

May 24-28, 2002 Nirmalya Parua

Overview of D0 Upgrade

May 24-28, 2002 Nirmalya Parua 

Upgrade Calorimeter Readout



2 Tesla solenoid magnetic field for central tracking system to facilitate charge and momentum measurement.



Silicon and fiber tracker detector.



Add scintillator detector in muon system for faster trigger



Add Pre-shower detectors.



Pipelined 3 Level trigger

Calibration Calorimeter FET

Upgrade of Calorimeter Readout

Cable replaced for impedence matching

Trig. sum Bank 0 SCA (48 deep) SCA (48 deep) Preamp/ Driver Filter/ Shaper x1 x8

peak base

preamp

1

driver

48

SCA (48 deep) SCA (48 deep) Bank 1

A D C A n. B u f f SCA(48 deep )

2” 55k readout channels

May 24-28, 2002 Nirmalya Parua

Fully instrumented with <0.1% bad readout channels.

Finer Debugging

             x8    x1 ADC L2  SCA L1                                 down  up        

L1 SCA up About 0.5% of

replaced .

are replaced L1 SCA down L2 SCA Good BAD

May 24-28, 2002 Nirmalya Parua DPF 2002

Pulser signal injected here

Calibration Using Pulser

May 24-28, 2002  Non linearity <0.5% for E>200 MeV  For Lower energy values non linearity is significant but can be parametrized.

Nirmalya Parua

Jet energy Scale

Correction of the jet energy measured at the detector level to the jet energy at the particle level Offset, E O : Energy that is not associated with the hard interaction. Namely Uranium noise, Pile-up effect, multiple interaction etc.

Response, R jet : Calorimeter energy response to jets, typically <1

Et=27 GeV

Measured by attributing energy imbalance in



+jet events.

Showering fraction S : Fraction of the jet energy that showered inside the cone. Depends on cone size.

May 24-28, 2002 Nirmalya Parua  +jet Event Et=24 GeV

Jet Studies for Run II

Data Sample - D0 RunII data taken during February and March 2002 - p



collisions at



s = 1.96 TeV

-

- Luminosity 1.9 pb –1 Selection Criteria - |



| < 0.5 and cone jet of size 0.7

- Jet selection criteria based on EMF, CHF, HotF, n90 are imposed - Missing E T < 0.7 p T jet 1 - |Z vtx | < 50 cm - E cal < 2 TeV

May 24-28, 2002 Nirmalya Parua

Jet triggers

Hardware Trigger: 

Triggering on Calorimeter towers.



Fast trigger readout



multi tower trigger



current coverage |



| <0.8

Software Triggers

Runs simple and fast jet algorithm on the precision readout.

May 24-28, 2002 Nirmalya Parua

Results

May 24-28, 2002 Nirmalya Parua

Multi jet events

2-jets event

• E T jet1 ~230GeV • E T jet2 ~190GeV May 24-28, 2002 Nirmalya Parua

3-jets event

• E T jet1 ~310GeV • E T jet2 ~240GeV • E T jet3 ~110GeV • E T ~8GeV DPF 2002

Summary

 D0 Detector is working well after upgrade.

 Jet measurements are well underway.

 First results available for Inclusive jet p T spectrum (60 GeV < p T < 360 GeV) Dijet mass spectrum ( 150 GeV < M <650 GeV)  Better understanding of the Detector and jet energy scale needed.

 Looking forward to more data.

May 24-28, 2002 Nirmalya Parua