Transcript Document
Upsilon production DØ
Penny Kasper
Fermilab
(DØ collaboration)
29 June 2006
Heavy Quarkonium Workshop
Brookhaven, June 2006
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
1
Outline:
– Tevatron and DØ detector
– ϒ(1S) Production
– ϒ(1S) Polarization
– Summary
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
2
Tevatron pp-collider
Run I (1992 – 1995) √s = 1.8 TeV
•delivered ~ 260 pb-1
Run II (2002-–
) √s = 1.96 TeV
•collisions every 396 ns
•rate to tape 50 Hz
•delivers ~ 15 pb-1/week (January 2006)
•max luminosity 1.58·1032 (January 2006)
detector
commissioning
Jul 2002
Feb 2002
April 2001
More than 1.4 fb-1 delivered &1.2 fb-1 recorded
data for physics
first
data for
analyses
So far reconstructed
~1 fb-1
~10x the total Run I data
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
3
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
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
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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
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
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Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
6
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
7
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) )
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
8
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
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
9
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
PDG: m(ϒ(1S)) = 9.46 GeV
m() = 9.423 ± 0.008 GeVm() = 9.415± 0.009 GeV m() = 9.403 ± 0.013 GeV
0 < |y | < 0.6
0.6 < |y | < 1.2
Kasper
All plots:Penny
3 GeV
< pt( < 4 GeV
Fermilab
Heavy Quarkonium Workshop
21 June 2006
1.2 < |y | < 1.8
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Efficiencies, correction factors…
Cross section
d2σ((1S))
dpt × dy
L
y
εacc
εtrig
N()
=
L × Δpt × Δy × εacc× εtrig× kdimu× ktrk× kqual
luminosity
rapidity
accept.•rec.eff.
trigger
0.0 < y < 0.6
εacc 0.15 - 0.26
εtrig
0.70
kdimu
0.85
ktrk
0.99
kqual
0.85
Penny Kasper
Fermilab
kdimu local muon reconstruction
ktrk tracking
kqual track quality cuts
0.6 < y < 1.2
0.19 – 0.28
0.73
0.88
0.99
0.85
1.2 < y < 1.8
0.20 - 0.27
0.82
0.95
0.95
0.93
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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
pb
680 ± 15 (stat) ± 18 (syst) ± 26 (lum)
for central y bin, expect factor 1.11 increase in cross
section from 1.8 TeV to 1.96 TeV (PYTHIA)
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
12
Normalized Differential Cross Section
shape of the pt
distribution does not
vary much with ϒ
rapidity
Reasonable
agreement with
calculation of Berger,
Qiu, Wang
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
13
Comparison with
previous results
only statistical uncertainties shown
PYTHIA
σ(1.2 < yϒ < 1.8)/σ(0.0 < yϒ < 0.6)
band = uncertainties of relative normalization
Penny Kasper
Fermilab
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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
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
15
Data selection
~ 1 fb -1
2 muons of opposite charge, Pt > 3.5 GeV
Systematic shift of J/psi position
is
-20MeV
Resolution of J/psi peak
is
75MeV
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
16
Dimuon mass vs. cos()
Mass spectrum fitted with a sum of 4 double gaussians plus
background
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
17
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
Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
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