Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June Upsilon production DØ Penny Kasper Fermilab (DØ collaboration) 29 June 2006 Heavy Quarkonium Workshop Brookhaven, June 2006

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June n Outline: –Tevatron and DØ detector –ϒ(1S) Production –ϒ(1S) Polarization –Summary

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June 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 1.58·10 32 (January 2006) - 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

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June 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 Fermilab Heavy Quarkonium Workshop 21 June DØ Muon Detector n 3 layers –Drift tubes and scintillation counters –One layer (A) inside of 1.8 T toroid n Good coverage: –Central |η| < 1 PDT –Forward 1 < |η| < 2 MDT n Fast and efficient trigger

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June Upsilon production n Quarkonium production is window on boundary region between perturbative and non-perturbative QCD n Factorized QCD calculations to O(α 3 ) (currently employed by PYTHIA) n color-singlet, color-evaporation, color-octet models n Different models –Shape of p t distribution –Absolute cross section –Polarization ϒ (1S) production at the Tevatron: –50% produced promptly –50% from decay of higher mass states (e.g. χ b →ϒ(1S)  )

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June Analysis Overview n Sample selection n 160 ± 10 pb-1 taken with dimuon trigger n 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) n pt (μ) > 3 GeV and |η (μ)| < 2.2 n At least one isolated μ ~ 50k ϒ (1S) events n Analysis n (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 n Get efficiencies and uncertainties

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June Fitting the Signal Signal: 3 states ( ϒ (1S), ϒ (2S), ϒ (3S)), described by Gaussians with masses m i, widths (resolution) σ i, weights c i,(i=1,2,3) –Masses m i = m 1 +  m i1 (PDG), widths σ i = σ 1 (m i /m 1 ), for i=2,3 –free parameters in signal fit: m 1, σ 1, c 1, c 2, c 3 n Background: 3rd order polynomial All plots: 3 GeV < p t (  < 4 GeV m(  ) = ± GeVm(  ) = 9.415± GeVm(  ) = ± GeV 0 < |y  | < < |y  | < < |y  | < 1.8 PDG: m(ϒ(1S)) = 9.46 GeV

Penny Kasper Fermilab 11 d 2 σ(  (1S)) dp t × dy N(  ) L × Δp t × Δy × ε acc × ε trig × k dimu × k trk × k qual = L luminosity k dimu local muon reconstruction y rapidity k trk tracking ε acc accept.rec.eff. k qual track quality cuts ε trig trigger 0.0 < y < < y < < y < 1.8 ε acc – ε trig k dimu k trk k qual Efficiencies, correction factors… n Cross section

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June < y ϒ < ± 19 (stat) ± 73 (syst) ± 48 (lum) pb 0.6 < y ϒ < ± 20 (stat) ± 76 (syst) ± 50 (lum) pb 1.2 < y ϒ < ± 19 (stat) ± 56 (syst) ± 39 (lum) pb 0.0 < y ϒ < ± 14 (stat) ± 68 (syst) ± 45 (lum) pb CDF Run I: 0.0 < y ϒ < ± 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)

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June Normalized Differential Cross Section shape of the p t distribution does not vary much with ϒ rapidity n Reasonable agreement with calculation of Berger, Qiu, Wang

Penny Kasper Fermilab 14 σ(1.2 < y ϒ < 1.8)/σ(0.0 < y ϒ < 0.6 ) PYTHIA Comparison with previous results band = uncertainties of relative normalization only statistical uncertainties shown

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June 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 +  cos 2 , –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 Fermilab Heavy Quarkonium Workshop 21 June 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 Data selection

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June Dimuon mass vs. cos(  ) Mass spectrum fitted with a sum of 4 double gaussians plus background

Penny Kasper Fermilab Heavy Quarkonium Workshop 21 June 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 p t ( ϒ) –First measurement of ϒ (1S) cross section at √s = 1.96 TeV. –Cross section values and shapes of dσ/dp t show only weak dependence on rapidity. –dσ/dp t is in good agreement with published results (CDF at 1.8 TeV) –Normalized dσ/dp t in good agreement with recent QCD calculations (Berger at al.) ϒ (1S) Polarization –Lots of data, results soon