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
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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
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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
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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
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Penny Kasper
Heavy Quarkonium Workshop
Fermilab
21 June 2006
7
Upsilon production
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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
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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
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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…
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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
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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
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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
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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
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Summary
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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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