# Presentation: 126079

## Cross Section for b-Jet Production

***D******Ø Collaboration***
***( Preliminary )***

- Fermilab B Physics Workshop
*February 24-26, 2000    WG-4*

- Arthur Maciel
-  **Northern Illinois University**
- for the

-  introduction
-  inclusive spectrum
-  tagging acceptance

-  data selection
-  b component
-   results

## Introduction

-  NLO production of jets containing heavy quarks
-  Loosely;  ‘MNR’(1992) + Snowmass Jet-Cone
-       at partonic level,   dσ =  dσ(open)  + dΔ (clustering)

** ****A new D****Ø look into b-production,**
-     complementary to open b-quark studies
-  **Jets are directly observable**
-  Less model dependence in connecting
-             observation with theory
-  Access to differential cross sections
**  ****Jet counting  (muon tagged jets);**
-  theory counts jets with b ( b-integrated)
-  DØ counts tagging muons (in jets)
- 	μ+ + μ–            b + b
- 	 2 B.R.           2

- =

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

**  ****b-Jets are jets carrying  b-flavor**

## Data Sample

- Run-1B (5.2±0.3) pb**–1  **muon **& **jet trigger
**L1: **muon PT > 4GeV  Jet Tower > 3GeV

| Jets  | Muons |
| --- | --- |
| ET > 25 GeV | PT > 6 GeV |
| | η | < 0.6 | | η | < 0.8 |
| ΔR = 0.7 | ΔR < 0.7 |

*Offline Selection*

-  PT**μ**>6GeV  b’s emerge from light bckgnd
-  muon exclusion (φ = ± 20°) around M.R.
-  “out of time” muon contamination < 1%
-  30K events

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

## Detection Efficiencies

- FNAL b-Wshop
- Feb. 24-26, 2000

|  | Jet | Muon |
| --- | --- | --- |
| Trigger | ET (85 - 100%) | PT (50 - 60%)* |
| Reco | 100% | PT (90 - 95%) |
| Offline | (97±1)% | (83±3)% |

**(*) Includes geom. acceptance**

- Combined

## Inclusive Spectrum

**Muon-Tagged Jets**

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

## Extraction of the b Component

-  PTRel templates from Isajet (b and non-b)
-  Fits to data using  Cernlib’s  “**HMCMLL”**
-  Individual b-fraction measurements at four
-     separate ET ranges; 20-25-35-50-100 GeV
-  Closure tests with Monte Carlo samples
-  Model dependence tests
-  PTRel discrimination power limits b-Jet
-      sample to ET < 100GeV
-  This is the dominant source of uncertainty

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

## x E-3

**χ****2**[2]** **=** 0.96**

| 2.65 | 1.35 | 0.48 | -0.01 |
| --- | --- | --- | --- |
|  | 1.45 | 1.52 | 1.56 |
|  |  | 2.22 | 2.67 |
|  |  |  | 3.39 |

***Covariance Matrix***

**x** E-3

***b -Component***

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

## b-Jets Spectrum

**b-Tagged Jets**

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

## Tagging Acceptance Corrections

_*Corrections due to*__;_
-  **Muon  ****η-range , p****T****-threshold**
** ****Muon-Jet association; ****ΔR<0.7**
** ****Unseen Jet-E****T****;  ( μ + ν )**
** ****B. R.   b ******** μ**
** ****Jet η-range **

- A(ET)–1 =

**Correct observed spectrum**
**with Monte Carlo ratio;**
- MC(bμ) parton jets, |η|<1
- MC(bμ)  analysis  image

- Correction  Uncertainties

-  **Correction factor does not depend on MC production rates**
** ****Fragmentation is the most relevant issue (fully correlated)**
** ****Lepton E****T ****correction sensitivity is minimized by kinematics**
**     ****constraints over fragmentation**

**Isajet 7.37 with CLEO decay modes**
**Frag (Peterson) ****ε**** = 0.006 ****±**** 0.003**
**Error = (+8% ; ****–****9%) E****T**** independent**

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

## Tagging Acceptance Corrections

**Tagging Acceptance Corrections**

- A(ET)

***Avoided use of event weights***
***•****** ******lower  P******T******b****** generation threshold***
***•****** ******higher P******T******b****** generation threshold***

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

- (%)

- (%)

## b-Jets Cross Section

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

**(*)** **2 ****μ****O**** ...**** ****μ****O****/2  ,  ****μ****O**** = (E****T****2**** + M****b****2****)****1/2**

## (Data-Theory) / Theory

- FNAL b-Wshop
- Feb. 24-26, 2000

***Systematic errors and their correlations ***
*** ******confer 80% C.L. to theory higher edge***

## Systematic Uncertainties Summary

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000

**Systematic Uncertainties Summary**

***( relative , percentual )***

## b-Quark Integrated Cross Section

**b-Quark Integrated Cross Section**

**(*)** **2 ****μ****O**** ...**** ****μ****O****/2  ,  ****μ****O**** = (P****b****T****2**** + M****b****2****)****1/2**

**(*)**

**A.Maciel**
- FNAL b-Wshop
- Feb. 24-26, 2000