Heavy Quarkonium Workshop
21 June 20061Penny Kasper
Fermilab
Upsilon production DUpsilon production DØØ
Penny KasperFermilab
(DØ collaboration)29 June 2006
Heavy Quarkonium WorkshopBrookhaven, June 2006
Heavy Quarkonium Workshop
21 June 20062Penny Kasper
Fermilab
Outline:– Tevatron and DØ detector– ϒ(1S) Production – ϒ(1S) Polarization– Summary
Heavy Quarkonium Workshop
21 June 20063Penny Kasper
Fermilab
Tevatron pp-colliderTevatron 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)
-
April 2001
Feb 2002
first data for
analyses
data for physics
detector commissionin
g
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
Heavy Quarkonium Workshop
21 June 20064Penny Kasper
Fermilab
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
Heavy Quarkonium Workshop
21 June 20065Penny Kasper
Fermilab
DDØ Muon Detector Ø 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
Heavy Quarkonium Workshop
21 June 20066Penny Kasper
Fermilab
Upsilon productionUpsilon 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) )
Heavy Quarkonium Workshop
21 June 20067Penny Kasper
Fermilab
Analysis OverviewAnalysis 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
Heavy Quarkonium Workshop
21 June 20068Penny Kasper
Fermilab
Fitting the SignalFitting 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
9Penny Kasper
Fermilab
d2σ((1S))
dpt × dy
N()
L × Δpt × Δy × εacc× εtrig× kdimu× ktrk× kqual
=
L luminosity kdimu local muon reconstructiony rapidity ktrk trackingεacc accept.•rec.eff. kqual track quality cuts εtrig trigger 0.0 < y < 0.6 0.6 < y < 1.2 1.2 < y < 1.8εacc 0.15 - 0.26 0.19 – 0.28 0.20 - 0.27 εtrig 0.70 0.73 0.82kdimu 0.85 0.88 0.95ktrk 0.99 0.99 0.95 kqual 0.85 0.85 0.93
Efficiencies, correction factors…Efficiencies, correction factors… Cross section
Heavy Quarkonium Workshop
21 June 200610Penny Kasper
Fermilab
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(Results: dσ(ϒϒ(1S))/dy × B((1S))/dy × B(ϒϒ(1S) (1S) →→ µ µ++µµ--))
for central y bin, expect factor 1.11 increase in cross section from 1.8 TeV to 1.96 TeV (PYTHIA)
Heavy Quarkonium Workshop
21 June 200611Penny Kasper
Fermilab
Normalized Differential Cross SectionNormalized Differential Cross Section
shape of the pt distribution does not vary much with ϒ rapidity
Reasonable agreement with calculation of Berger, Qiu, Wang
12Penny Kasper
Fermilab
σ(1.2 < yϒ < 1.8)/σ(0.0 < yϒ < 0.6)
PYTHIA
Comparison with Comparison with previous resultsprevious results
band = uncertainties of relative normalization
only statistical uncertainties shown
Heavy Quarkonium Workshop
21 June 200613Penny Kasper
Fermilab
PolarizationPolarization 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
Heavy Quarkonium Workshop
21 June 200614Penny Kasper
Fermilab
Systematic shift of J/psi position
is -20MeV
Resolution of J/psi peakis
75MeV
~ 1 fb -1 2 muons of opposite charge, Pt > 3.5 GeV
Data selection
Heavy Quarkonium Workshop
21 June 200615Penny Kasper
Fermilab
Dimuon mass vs. cos(Dimuon mass vs. cos())
Mass spectrum fitted with a sum of 4 double gaussians plus background
Heavy Quarkonium Workshop
21 June 200616Penny Kasper
Fermilab
SummarySummary 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