# Presentation: 211658

## 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

## Jets

- Jet is a collection of towers within a given cone R

- Where  is the azimuthal coordinate
-  is the pseudorapidity  = -ln tan(/2)

## Calorimeter Overview

**Liquid argon sampling**
**Stable, uniform response, rad. hard, fine spatial seg****.**
**LAr purity important ( impurity <0.5 ppm)**
**Uranium absorber (Cu or Steel for coarse hadronic)**
**Compensating e/******** ******** 1, dense ******** compact****  **
**Uniform, hermetic with full coverage**** **
******< 4.2 (******** ******** 2****o****), ********int ********total) **
**Energy Resolution**
**e: ********E**** / ****E**** ****= 15%**** /********E********+ 0.3%  ********:  ********E**** / ****E**** ****= 45%**** /********E +  4%   (as measured in Run I)**

- Drift time 430 ns

**Z**

**X**

**Y**

## 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**

## Jets in Run I

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

## Fermilab Accelerator Upgrade

- 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
- 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

## Bunch Structure

- Detector readout and trigger system upgrade must take into account smaller bunch crossing time

## 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. **

## Overview of D0 Upgrade

**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**

## Upgrade of Calorimeter Readout

**Bank 1**

**Preamp/**
**Driver**

**Trig. sum**

**Filter/**
**Shaper**

**x1**

**x8**

**SCA (48 deep)**

**SCA (48 deep)**

**SCA (48 deep)**

**SCA (48 deep)**

**Bank 0**

**Calorimeter**

**Calibration**

**55k readout channels**

- A n. Bu
- f
- f

- A
- D
- C

- 48

- 1

- peak

- base

- Cable replaced for impedence matching

**Fully instrumented with <0.1% bad readout channels.**

## Finer Debugging

- 

- 

- 

- 

-     

- x8

- x1

- L1 SCA

- up

- L2 SCA

- ADC

- down

- About 0.5% SCA chips
- replaced.

**About 0.5% of the SCA chips are replaced**

**BAD**

**Good**

- D0-France 28/11/2001

## Calibration Using Pulser

- Pulser signal injected here

- Non linearity <0.5% for E>200 MeV
- For Lower energy values non linearity is significant but can be parametrized.

## Jet energy Scale

**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**
**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.**** **

**Correction of the jet energy measured at the detector level to the jet energy at the particle level**

## 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**

- -

## 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.**

## Results

## Multi jet events

**  ****2-jets event**
-  ETjet1~230GeV
-  ETjet2~190GeV

**  ****3-jets event**
-  ETjet1~310GeV
-  ETjet2~240GeV
-  ETjet3~110GeV
-  ET~8GeV

- reunion du vendredi 14/12/2001

## Summary

- D0 Detector is working well after upgrade.
- Jet measurements are well underway.
- First results available for
-    Inclusive jet pT spectrum (60 GeV < pT < 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.