Inclusive b-quark and upsilon production in D Ø

1. Inclusive b-quark and upsilon production in DØ Horst D. Wahl Florida State University DIS 2005, Madison

2. Outline • Tevatron and DØ detector • Bottomonium ϒ(1S) production • High pt μ-tagged jet production • conclusion

3. Tevatron – data taking • peak luminosity in 2005 above 1032 cm-2 s-1 • DØ collected > 690 pb-1 • Results shown use 150 - 300pb-1

4. Next to leading order Leading order Flavor excitation Flavor creation Gluon splitting

5. Recent developments • Beyond NLO: resummation of log(pt/m) terms  FONLL • Changes in extraction of fragmentation function from LEP data • New PDFs • Improved treatment of experimental inputs (use b-jets and b-hadrons instead of b-quarks)

6. Open Heavy Flavor Production • Long-standing “discrepancies” between predicted and measured cross sections now resolved; e.g. Cacciari, Frixione, Mangano, Nason, Ridolfi,JHEP 0407 (2004) 033 • combined effects of • better calculations (Fixed order (NLO)+ NLL= FONLL) • relationship/difference between e+e−and hadron colliders • different moments of FF relevant • better estimate of theory errors (upward!) • new appreciation of issues with“quark-level” measurements • Total Cross sections (from CDF): • –inclusive b cross section: |y<1| 29.4±0.6±6.2 µb hep-ex/0412071 (submitted to PRD) • inclusive c cross section: ~50x higherPRL 91, 241804 (2003)

7. Comments: Tevatron as HF Factory • 􀂃The cross sections given on the previous slide imply • central (|y|<1) b’s at 3kHz at current luminosities • ~2x this if you look out to |y|<2 • central charm at 150kHz • –~2x1010 b’s already seen by CDF and DØ in Run II • –~1x1012 charm hadrons already produced(!) • ⇒ Near infinite statistics for some measurements • ⇒ If you can trigger... • Rely heavily on muon triggers • J/ψ decays are golden • semi-leptonic decays- • rare decays with leptons • Tracks with significant b/σb • Missing neutrals troublesome • forget o identification • all-charged decay modes

8. The DØ Detector Muon Toroid Calorimeter Solenoid, Tracking System (CFT, SMT)

11. DØ tracking system Silicon Tracker Fiber Tracker 125 cm h=1.6 h=3 50cm 20cm Forward Preshower detector Solenoid Central Preshower detector

12. DØ - Muon detectors A-f Scint PDT’s Forward Trigger Scint Shielding Forward Tracker (MDTs) Bottom B/C Scint • Toroid magnet (1.9 T central, 2.0 T forward) • Scintillation counters • PDTs (central) • MDTs (forward)

13. Bottomonium production • Theory modeling of 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 • Recent calculations by Berger et al. combining separate perturbative approaches for low and high-pt regions • Predict shape of pt distribution • Absolute cross section not predicted • ϒ(1S) Production @ Tevatron: • 50% produced promptly, i.e. at primary vertex • 50% from decay of higher mass states (e.g. χb →ϒ(1S) ) • Event selection • - luminosity: 159.1 ± 10.3 pb-1 • - di-muon: pT>3, tight Tracking and Calorimeter isolation cut • - invariant mass in 7 – 13 GeV

14. Why measure ϒ(1S) production at DØ • Because we can: The ϒ(1S) cross-section had been measured at the Tevatron (Run I measurement by CDF) up to a rapidity of 0.4. DØ has now measured this cross-section up to a rapidity of 1.8 at √s = 1.96 TeV • Measuring the ϒ(1S) production cross-section provides an ideal testing ground for our understanding of the production mechanisms of heavy quarks. There is considerable interest from theorists in these kinds of measurements: • E.L. Berger, J.Qiu, Y.Wang, Phys Rev D 71 034007 (2005) and hep-ph/0411026; • V.A. Khoze , A.D. Martin, M.G. Ryskin, W.J. Stirling, hep-ph/0410020

15. The Analysis • Goal: • Measuring the ϒ(1S) cross-section in the channel • ϒ(1S) → μ+μ- as a function of pt in three rapidity ranges: • 0 < | yϒ| < 0.6, 0.6 < | yϒ | < 1.2 and 1.2 < | yϒ | < 1.8 • Sample selection • Opposite sign muons • Muon have hits in all three layers of the muon system • Muons are matched to a track in the central tracking system • pt (μ) > 3 GeV and |η (μ)| < 2.2 • At least one isolated μ • Track from central tracking system must have at least one hit in the Silicon Tracker

16. Efficiencies,… N(¡) d2σ(¡(1S)) = L × Δpt × Δy × εacc× εtrig× kdimu× ktrk× kqual dpt× dy • Cross section: L Luminosity kdimu local muon reconstruction y rapidity ktrk tracking εacc Acceptance kqual track quality cuts εtrig Trigger 0.0 < y < 0.6 0.6 < y < 1.2 1.2 < y < 1.8 εacc 0.15 - 0.26 0.19 – 0.28 0.20 - 0.27 εtrig 0.70 0.73 0.82 kdimu 0.85 0.88 0.95 ktrk 0.99 0.99 0.95 kqual 0.85 0.85 0.93

17. Data vs Monte Carlo • To determine our efficiencies, we only need an agreement between Monte Carlo and data within a given pT(ϒ) and y(ϒ) bin and not an agreement over the whole pT(ϒ) and y(ϒ) range at once . MC Data* η(μ) φ(μ) pt(μ) in GeV 0 5 10 15 20 -2 -1 0 1 2 0 3 6 0.6 < | yϒ| < 1.2 *9.0 GeV < m(μμ) < 9.8 GeV

18. 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(¡(1S)) = 9.46 GeV m(¡) = 9.415± 0.009 GeV m(¡) = 9.403 ± 0.013 GeV m(¡) = 9.423 ± 0.008 GeV 1.2 < |y¡ | < 1.8 0.6 < |y¡ | < 1.2 0 < |y¡ | < 0.6 All plots: 3 GeV < pt(¡) < 4 GeV

19. 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 < 0.4 680 ± 15 (stat) ± 18 (syst) ± 26 (lum) pb Fro central y bin, expect  factor 1.11 increase in cross section from 1.8TeV to 1.96 TeV (Pythia)

20. Comparison with previous results σ(1.2 < yϒ < 1.8)/σ(0.0 < yϒ < 0.6) Pythia

21. Effects of polarization • CDF measured ϒ(1S) polarization for |yϒ| < 0.4. How can we be sure that our forward ϒ(1S) are not significantly polarized ? • So far there is no indication for ϒ(1S) polarization. • CDF measured α = -0.12 ± 0.22 for pT (ϒ)> 8 GeV • α = 1 (-1) ⇔ 100% transverse (longitudinal) polarization • The vast majority of our ϒ(1S) has pT(ϒ) < 8 GeV • Theory predicts that if there is polarization it will be at large pT. • No evidence for polarization in our signal (|y| < 1.8); ---- not enough data for a fit in the forward region alone. • estimated the effect of ϒ(1S) polarization on our cross-section: • Even at α = ± 0.3 the cross-section changes by 15% or less in all pT bins. • same effect in all rapidity regions.

22. Question: Why is CDF's systematic error so much smaller than ours ? • Better tracking resolution --- CDF can separate the three ϒ resonances: → Variations in the fit contribute considerable both to our statistical and systematic error. → We believe we have achieved the best resolution currently feasible without killing the signal • Poor understanding of our Monte-Carlo and the resulting large number of correction factors. • Signal is right on the trigger turn-on curve.

23. Conclusions • 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. • Shapes of dσ/dpt show very little dependence on rapidity. • Normalized dσ/dpt is in good agreement with published results (CDF at 1.8TeV) • μ-tagged jet cross section: • Measured dσ/dpt in central rapidity region |y|<0.5forμ-tagged jets originating from heavy flavor

24. Motivation Fact: The multi-generational structure of the quark doublets requires explanation and could herald compositeness. Under hypothesis of compositeness, deviation from point-like behavior would likely manifest in third generation. Conclusion: g  bb may exhibit desired deviant behavior. Explore b quark dijet mass as a possible signature. • Problem • ~100:1 QCD:bb Solutions • m tagging • 2nd VTX tagging • Impact parameter CDF: PRL 82 (1999) 2038 Fit to CDF qQCD calculation

25. m-tagged Jet Cross-section eT Trigger Eff ePV Primary Vertex Eff ej Jet Eff emm Eff fbm Frac b  m(Pt > 4 GeV) fBm Frac B  m(Pt > 4 GeV) L Luminosity Dpt Pt bin width sHF HF cross-section sbg background cross-section • Given the simplicity of the calculation, there are few likely sources of the excess seen in p13. These could conceivably be • N • m JES (central value) • Resolution (i.e. smearing) Correlated Jet + m (Pt > 5 GeV) p13

26. p14 Analysis Summary • Inclusive m-tagged jet • corrJCCB (0.5 cone jets) • Standard Jet quality cuts, Standard JET Triggers • Jet tagged with MEDIUM muon • (more on this later) • DR(m, jet) < 0.5 • |yjet| < 0.5 • JES 5.3 • Long term goal was b-jet xsec. Difficult due to no data-driven determination of b-fraction.

27. p14 Skimming • Start with CSG QCD skim • Turn into TMBTrees (40M events…on disk) • Skim on Trees • Remove bad runs (CAL, MET, SMT, CFT, JET, Muon) • Remove events w/o 2 jets • Use Ariel d0root_ based package • SKIM 1:  1 leading jet has ~ MEDIUM m (P(m) > 4 GeV) • SKIM 2:  1 leading jet has ~ loose SVT

28. p14 All Data: CSG Skims Bad runs & lumblk removed in luminosity. Only bad run removed in event counts for skims. Up until Run 193780 (07-JUN), V12.37.

29. Trigger Turn On • Jet Trigger • Collinear muon • |yjet| < 0.5 • Luminosity weighted • Statistics uncorrelated poisson • (wrong, of course) • JES corrected (5.3)

30. Efficiencies…. [0.37 ± 0.05]

31. m JES Definitions • Required identically 2 jets • Pt(jet 3, uncor) < 8 OR third jet doesn’t pass jet QC • One jet contains muon, the other doesn’t. • | Df | > 2.84 • Imbalance variable: • Independent variable:

32. Jet energy scale for μ-tagged jets • μ-tagged jets also have neutrinos ⇒offset -- correction needed • Imbalance in events with 2 jets (one with, one without μ) – find 3.8% offset, not strongly pt dependent for pt in (75, 250GeV) • Scale energies of μ-tagged jets by factor 1.038 • Order-randomized imbalance used to get resolution STD JES 5.3 gives a 3.8% offset for m-tagged jets. It is independent of Pt (75-250 GeV). Maybe higher above that. Need to rebin and revisit the idea that the muon Pt may be mis-measured. Same plot when scaling the m-tagged jet energies by 3.8%.

33. Energy Resolution

34. resolution • Neutrinos in μ-tagged jet  resolution worse than for jets without μ • take rms of order randomized imbalance • Parameterize, Fit (fig. (a)) • Subtract (in quadrature) resolution for jets without μ obtain resolution for μ-tagged jets (fig. (b) • Fit: • N = 7.7  4.1 • S = 1.9  0.1 • C = 0.0  0.1 • Resolution parameterization used in “unsmearing”

35. Fitting Functions

36. Extraction of Correction Factors “normal” exponential

37. Point by Point Unsmearing Factors “normal” Exponential Unsmearing Error small ~5% for Pt > 100 GeV

38. HF fraction of μ-tagged jet sample • Sample of jets with μ-tagged jets contains jets with μ from non-HF sources (e.g. , K decays…) • Use Pythia with standard DØ detector simulation to find HF fraction of jets tagged with muons vs (true) pt • Fit with A + B e-Pt/C • A = “plateau”, • B = “zero” • C = “turnon”

39. Pythia using standard DØ MC. • NLO uses NLO++ (CTEQ6L) • From Pythia, find fraction of jets tagged with muons (HF only). • Multiply NLO cross-section by Pythia muon-fraction. • This is effectively the NLO k factor.

40. Conc • DØ Note and Conference note to EB025 • Residual small bug in code (should have only a few percent effect). • JES error must be reduced to use this before setting limits on new physics.