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Measurement of heavy-flavour production down to low p T with ALICE

Measurement of heavy-flavour production down to low p T with ALICE. Andrea Dainese INFN – Legnaro for the ALICE Collaboration. Layout. Heavy-flavour production at LHC baseline predictions (pQCD) Heavy quarks as probes of the initial state importance of low p T measurements

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Measurement of heavy-flavour production down to low p T with ALICE

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  1. Measurement of heavy-flavour production down to low pT with ALICE Andrea Dainese INFN – Legnaro for the ALICE Collaboration High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  2. Layout • Heavy-flavour production at LHC • baseline predictions (pQCD) • Heavy quarks as probes of the initial state • importance of low pT measurements • Why ALICE is well-suited for these measurements • Strategies and expected performance for: • D0 K-p+ • B  e + X • Summary High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  3. c and b production in pp at the LHC:testing QCD at s = 14 TeV • Important test of pQCD in a new energy domain (7sTEVATRON) • remember the “15-years saga of b production at the Tevatron”*… • …and D production not yet fully reconciled  Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033 CDF, PRL91 (2003) 241804 FONLL: Cacciari, Nason * M.Mangano High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  4. pQCD predictions for the LHC Compare predictions by several different models (HERA-LHC Workshop) CERN/LHCC 2005-014 hep-ph/0601164 charm beauty Good agreement between collinear fact.-based calculations: FO NLO (Mangano, Nason, Risolfi) and FONLL (Cacciari, Nason) kT fact. CASCADE (Jung) higher at large pT High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  5. Theoretical Uncertainties Evaluation of theoretical uncertainties (HERA-LHC Workshop) CERN/LHCC 2005-014 hep-ph/0601164 charm beauty MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  6. ALICE baseline yields • Cross sections: NLO (MNR code) • mc=1.2 GeV, mF=mR=2mc; mb=4.75 GeV, mF=mR=mb • Yields: assuming sppinel = 70 mb at 14 TeV High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  7. increasing s charm beauty Cartoon c and b production at the LHC:a probe of small-x gluons • Probe unexplored small-x region with HQs at low pT and/or forward y • down to x~10-4 with charm already at y=0 • Window on the rich phenomenology of high-density PDFs • gluon saturation / recombination effects • breakdown of factorization ? High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  8. Deviations from pQCD baselinedue to small-x effects?maybe already in pp ...“Small-x effects in heavy-quark production in pp”in HERA-LHC workshop proceedings CERN/LHCC 2005-014 hep-ph/0601164 (A.D., K.Eskola, V.Kolhinen, K.Kutak, H.Jung, K.Peters, R.Vogt) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  9. R Eskola, Honkanen, Kolhinen, Qiu, Salgado, NPB660 (2003) 211 GLR-MQ non-linear term in DGLAP eq. non-linear (quadratic) correction has “–” sign Q2 evolution is slower Refit HERA F2 data, reduces F2 at low x and moderate Q2 xg(x,Q2) at low Q2 (<10 GeV2) and x (<10-3) is larger than in DGLAP High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  10. × Non-linear effects in BK equation Kutak, Kwiecinski, Martin, Stasto Non-linear part has no impact in the kinematical region of HERA H.Jung et al., CASCADE MC with CCFM uPDFs and KKMS nonlinear term High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  11. GLR-MQ vs BK: gluons R = 5 GeV-1 = 1 fm R = 4 GeV-1 = 0.8 fm Caveat: LO! Linear (dashed) vs non-linear (solid) in BK with R = 4 GeV-1 Linear (blue) vs non-linear (red) in DGLAP Kutak, Kwiecinski, Martin, Stasto Eskola, Honkanen, Kolhinen, Qiu, Salgado, NPB660 (2003) 211 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  12. c c Charm at s = 14 TeV: x,Q2 range (1) • Simple estimate: High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  13. Charm at s = 14 TeV: x,Q2 range (2) • PYTHIA simulation (LO): High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  14. Charm at s = 14 TeV: x,Q2 range (3) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  15. Non-linear effects on charm in pp pp @ 14 TeV R = 0.6 fm R = 0.3 fm |y| < 1 R = 1 fm Charm enhancement due to non-linear effects in GLR-MQ Charm suppression due to non-linear effects in BK Dainese, Bondila, Eskola, Kolhinen, Vogt, JPG30 (2004) 1787 H.Jung et al., CASCADE MC with CCFM uPDFs and KKMS nonlinear term High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  16. c c Probing nuclear initial state with HQs • Shadowing in pA (AA) • CGC in pA (AA) • Double parton scattering in pA High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  17. c c Probing nuclear initial state with HQs • Shadowing in pA (AA) • CGC in pA (AA) • Double parton scattering in pA Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  18. c c Probing nuclear initial state with HQs • Shadowing in pA (AA) • CGC in pA (AA) • Double parton scattering in pA • Saturation scale Qs2(x) ~ xg(x)A/RA2 ~ xg(x)A1/3 • At LHC for x~10-4, Qs~2-2.5 GeV > mc • For mT,c~Qs, charm prod. CGC-dominated: • suppression: scales with Npart in pA (not Ncoll) • harder pT spectra, since typical kT~Qs~2 GeV, while • in standard factorization kT~LQCD~0.2 GeV Kharzeev, Tuchin, NPA 735 (2004) 248 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  19. c c predicted rate: cccc/cc ~ 10% (Treleani et al.) signature: events with “tagged” DD (can use D0+e+ or e+e+) and ch. conj. NB: there is a “background” from normal bb events, but it can be estimated from measured single inclusive b cross section Probing nuclear initial state with HQs • Shadowing in pA (AA) • CGC in pA (AA) • Double parton scattering in pA probe “many-body” PDFs normal and anomalous: different A dep. Cattaruzza, Del Fabbro, Treleani, PRD 70 (2004) 034022 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  20. The ALICE Detector |h| < 0.9, B = 0.5 T TPC + silicon tracker g,e, p, K, p identification -4 < h < -2.5 muons High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  21. ALICE heavy-flavour potential HERA-LHC Workshop CERN/LHCC 2005-014 hep-ph/0601164 • ALICE combines electronic (|h|<0.9), muonic (-4<h<-2.5), hadronic (|h|<0.9) channels • ALICE covers low-pT region • ALICE covers central and forward regions • Precise vertexing in the central region to identify D (ct ~ 100-300 mm) and B (ct ~ 500 mm) decays A.Dainese (ALICE) M.Smizanska (ATLAS) C.Weiser (CMS) U.Uwer (LHCb) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  22. central rapidity (this talk) talks by M.Gagliardi, D.Stocco Heavy-flavour analyses • Hadronic decays: • D0K-p+, D*+D0p+, D+K-p+p+, Ds+K+K0*/fp+… • Leptonic decays: • B e/m + X • Invariant mass analysis of lepton pairs: BB, DD, BDsame, J/y, y’,  family, B J/Y + X • BB m m m (J/ym) • e-m correlations In red, channels studied for the PPR Volume 2 CERN/LHCC 2005-030 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  23. rf: 50 mm rec. track e z: 425 mm Primary Vertex PIXEL CELL B < 60 mm (rf) for pT > 1 GeV/c d0 X Two layers: r = 4 cm r = 7 cm Vertexing: track d0 resolution Resolution mainly provided by the 2 layers of silicon pixels  9.8 M High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  24. D0 K-p+: Invariant mass analysis • Example (extrapolated to expectation for 109 pp events): 0.5-1 GeV/c 3-4 GeV/c 12-14 GeV/c High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  25. inner bars: stat. errors outer bars: stat.  pt-dep. syst. not shown: 9% (Pb-Pb), 5% (pp, p-Pb) normalization errors D0 K-p+: Results 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) + 1 year with 1month of p-Pb running (108 p-Pb events) Down to pT ~ 0 in pp and p-Pb (1 GeV/c in Pb-Pb) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  26. rec. track e Primary Vertex B d0 X B  e + X: Detection strategy • Electron PID: reject most of the hadrons • d0 cut: reduce charm and bkg electrons (Dalitz, g conv.) • Subtract (small) residual background (ALICE data + MC) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  27. inner bars: stat. errors outer bars: stat.  pT-dep. syst. errors not shown: 5% normalization error Using electrons in 2 < pT < 20 GeV/c obtain B meson 2 < pTmin < 30 GeV/c MC-based procedure à la UA1 B  e + X: Results 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  28. Comparison to pQCD predictions pp, s = 14 TeV charm (D0  Kp) beauty (B  e+X) 1 year at nominal luminosity (109 pp events) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  29. Data: mc = 1.2 GeV, Q2 = 4mT2 and enhancement Data: mc = 1.3 GeV, Q2 = mT2 and enhancement How to detect the enhancement due to nonlinear effects? • The idea is that the effect (enh. only at very low pt) cannot be mimicked by NLO pQCD • In practice: consider ratio “Data/Theory” for all reasonable choices of theory parameters Dainese, Bondila, Eskola, Kolhinen, Vogt, JPG30 (2004) 1787 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  30. p-Pb pp Sensitivity to D0 RpA at |y|<1 Example with shadowing R.Grosso, PhD thesis (2004) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  31. Summary • Charm and beauty production study at the LHC: • test of QCD in a new energy domain • at low pT: access to small-x gluon dynamics; saturation? • ALICE is well-equiped for heavy-flavour studies • using several different channels / strategies • acceptance down low pT at central and forward rapidity • small extrapolation for total cross section • sensitivity to small-x QCD • Predictions are welcome! High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  32. EXTRA SLIDES High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  33. LHC running conditions pp nominal run Pb-PB nominal run Ldt dt = 3.1030 cm-2 s-1 x 107 s 5.1037 cm-2 for pp run, 14 TeV Npp collisions = 2 .1012 collisions Ldt = 5.1026 cm-2 s-1 x 106 s 5.1032 cm-2 PbPb run, 5.5 TeV NPbPb collisions = 2 .109 collisions   Muon triggers: ~ 100% efficiency, < 1kHz Muon triggers: ~ 100% efficiency, ~ 1kHz Electron triggers: ~ 50% efficiency of TRD L1 20 physics events per event Electron triggers: Bandwidth limitation NPbPb central = 2 .108 collisions Hadron triggers: Npp minb = 2 .109 collisions Hadron triggers: NPbPb central = 2 .107 collisions   High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  34. fraction of misidentified pions Electron ID • D and B mesons have 10% B.R. to electrons • Combined info from TRD (trans. rad.) and TPC (dE/dx) • TRD rejects 99% of the p and ALL heavier hadrons (pT > 1 GeV/c) • TPC further rejects residual pions (up to 99% at low p) • About 20% of electrons rejected High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

  35. Effect of electron identification residual charm contribution subtracted using D0 measurement  3-5% syst. error High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

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