Upsilon production D Ø

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



Fermilab

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



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



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



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



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) )



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



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



Fermilab

0.0 < yϒ < 0.6 732 ± 19 (stat) ± 73 (syst) ± 48 (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)



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



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



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



Fermilab

Dimuon mass vs. cos(Dimuon mass vs. cos())

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



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

Upsilon production D Ø

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