# Presentation: 102166

## Upsilon production  DØ

- Penny Kasper
- Fermilab
- (DØ collaboration)
- 29 June 2006
- Heavy Quarkonium Workshop
- Brookhaven, June 2006

## Outline:
Tevatron and DØ detector
Υ(1S) Production 
Υ(1S) Polarization
Summary

- Tevatron and DØ detector
- Υ(1S) Production
- Υ(1S) Polarization
- Summary

## -

**April 2001**

**Feb 2002**

**first data for analyses**

** ****data for physics**

** ****detector commissioning**

**Jul 2002**

-  So far reconstructed

**More than 1.4 fb****-1**** delivered &1.2 fb****-1 ****recorded**

** ****~1 fb-1**
** ****~10x the total Run I  data**

## The DZero Experiment

- Silicon tracker
- Coverage up to |η| <2
- New Layer 0
- Fiber tracker
- Coverage up to | η | <2
- 8 double layers
- Solenoid (2 Tesla)
- Forward + central muon system
- Coverage up to | η | <2
- Three level trigger system
- Outputs 50 Hz

## DØ Muon Detector 

- 3 layers
- Drift tubes and scintillation counters
- One layer (A) inside of 1.8 T toroid
- Good coverage:
- Central  |η| < 1 PDT
- Forward  1 < |η| < 2  MDT
- Fast and efficient trigger

## Upsilon production

- Quarkonium production is window on boundary region between perturbative and non-perturbative QCD
- Factorized QCD calculations to O(α3) (currently employed by PYTHIA)
- color-singlet, color-evaporation, color-octet models
- Different models
- Shape of pt distribution
- Absolute cross section
- Polarization

- Υ(1S) production at the  Tevatron:
- 50% produced promptly
- 50% from decay of higher mass states (e.g. χb →Υ(1S) )

## Analysis Overview

- Sample selection
- 160 ± 10 pb-1  taken with dimuon trigger
- Opposite sign muons with hits in all three layers of the muon system, matched to a track in the central tracking system (with hit in SMT)
-  pt (μ)  > 3 GeV and |η (μ)|  < 2.2
-  At least one isolated μ
- ~ 50k Υ(1S) events
- Analysis
- (μ+μ-) mass resolution functions obtained from J/ψ and MC studies
- Fit (μ+μ-) mass spectra for different y and pt bins, assuming 3 Υ states and background
- Get efficiencies and uncertainties

## Fitting the Signal

- Signal: 3 states (Υ(1S), Υ(2S), Υ(3S)),  described by Gaussians with masses mi,  widths (resolution) σi, weights  ci ,(i=1,2,3)
- Masses mi= m1+ m i1(PDG), widths σi = σ1 • (mi/m1), for i=2,3
- free parameters in signal fit:  m1, σ1, c1, c2, c3
- Background: 3rd order polynomial

-  All plots: 3 GeV < pt(  < 4 GeV

- m() = 9.423 ± 0.008 GeV

- m() = 9.415±  0.009 GeV

- m() = 9.403 ± 0.013 GeV

- 0 < |*y* | < 0.6

- 0.6 < |*y* | < 1.2

- 1.2 < |*y* | < 1.8

- PDG: m(Υ(1S)) = 9.46 GeV

## Efficiencies, correction factors...

- L     luminosity                     kdimu  local muon reconstruction
- y     rapidity                          ktrk      tracking
- εacc   accept.•rec.eff.             kqual   track quality cuts
- εtrig    trigger

-       0.0 < y < 0.6    0.6 < y < 1.2     1.2 < y < 1.8
- εacc    0.15 - 0.26      0.19 – 0.28        0.20 - 0.27
- εtrig             0.70               0.73                   0.82
- kdimu          0.85               0.88                   0.95
- ktrk              0.99               0.99                   0.95
- kqual        0.85               0.85                   0.93

- Cross section

## Results: dσ(Υ(1S))/dy × B(Υ(1S) → μ+μ-)

- 0.0 < yΥ < 0.6          732 ± 19 (stat) ± 73 (syst) ± 48 (lum)  pb
- 0.6 < yΥ < 1.2          762 ± 20 (stat) ± 76 (syst) ± 50 (lum)  pb
- 1.2 < yΥ < 1.8          600 ± 19 (stat) ± 56 (syst) ± 39 (lum)  pb
- 0.0 < yΥ < 1.8          695 ± 14 (stat) ± 68 (syst) ± 45 (lum)  pb

- CDF Run I:
- 0.0 < yΥ < 0.4          680 ± 15 (stat) ± 18 (syst) ± 26 (lum) pb

- Results: dσ(Υ(1S))/dy × B(Υ(1S) → μ+μ-)

- for central y bin, expect factor  1.11 increase in cross section from 1.8 TeV to 1.96 TeV (PYTHIA)

## Normalized Differential Cross Section

- shape of the pt distribution does not vary much with Υ rapidity
- Reasonable  agreement with calculation of Berger, Qiu, Wang

## Comparison with previous results

- σ(1.2 < yΥ < 1.8)/σ(0.0 < yΥ < 0.6)

- PYTHIA

- Comparison with previous results

- band = uncertainties  of relative normalization

- only statistical uncertainties shown

## Polarization

- NRQCD predicts that (1S) will be produced with increasing transverse polarization as pt increases. The Color Evaporation Model predicts no polarization.
- Angular distribution ~  1 +  cos2,
- Where  is the angle between + in the S rest frame and the direction of the S in the lab frame
-   = +1   Transverse polarization
-   = -1   Longitudinal polarization

## Data selection

**Systematic shift of J/psi position **
**is**
** ****-20MeV**
**Resolution of J/psi peak**
**is**
**75MeV **

** ****~ 1 fb -1 **
**2 muons of opposite charge,  Pt > 3.5 GeV**

- _x0018_

**Data selection**

## Dimuon mass vs. cos()

- Mass spectrum fitted with a sum of 4 double gaussians plus background

## Summary

- Υ(1S) cross-section
- Presented measurement of Υ(1S) cross section • BR(→μμ) for 3 different rapidity bins out to  y(Υ) = 1.8, as a function of pt(Υ)
- First measurement of  Υ(1S) cross section at  √s = 1.96 TeV.
- Cross section values and shapes of  dσ/dpt show only weak  dependence on rapidity.
- dσ/dpt is in good agreement with published results (CDF at 1.8 TeV)
- Normalized dσ/dpt in good agreement with recent QCD calculations (Berger at al.)
- Υ(1S) Polarization
- Lots of data,  results soon