Heavy Quarks in view of the LHC

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Heavy Quarks in view of the LHC. Andrea Dainese INFN (ALICE Collaboration). PARTON ENERGY LOSS. Layout. High- p T (heavy-flavour) particle production in hadronic collisions –from pp to AA– in factorized QCD pp baseline: pQCD calculations nuclear effects, in initial and final state - PowerPoint PPT Presentation

Text of Heavy Quarks in view of the LHC

  • Heavy Quarks in view of the LHCAndrea DaineseINFN(ALICE Collaboration)

    Frankfurt, 07.12.2006 Andrea Dainese

  • LayoutHigh-pT (heavy-flavour) particle production in hadronic collisions from pp to AA in factorized QCDpp baseline: pQCD calculationsnuclear effects, in initial and final state

    What have we learnt at Tevatron and RHIC?

    What will be new at the LHC?What do we expect? What should we measure?

    Experimental Perspectives at the LHC

    Frankfurt, 07.12.2006 Andrea Dainese

  • Heavy-flavour production: ppproton-proton collisions: factorized pQCD approach

    Frankfurt, 07.12.2006 Andrea Dainese

  • pp QQ: pQCD calculations vs dataCalculation of partonic cross section standard: Fixed Order (NLO) Massive (e.g. MNR code)

    state-of-the-art: Fixed Order Next-to-Leading Log (FONLL) more accurate at high pTQM06 update later

    Frankfurt, 07.12.2006 Andrea Dainese

  • Heavy-flavour production: AAAA Binary scaling for hard yields:Binary scaling is broken by:

    Frankfurt, 07.12.2006 Andrea Dainese

  • Calculating Parton Energy LossBaier, Dokshitzer, Mueller, Peigne, Schiff, NPB 483 (1997) 291.Zakharov, JTEPL 63 (1996) 952.Salgado, Wiedemann, PRD 68(2003) 014008.BDMPS-Z formalismRadiated-gluon energy distrib.:transport coefficientsets the scale of the radiated energyrelated to constraint kT < w, controls shape at w
  • Model vs RHIC light dataModel: pQCD + E loss probability + detailed collision geometryDensity ( ) tuned to match RAA in central Au-Au at 200 GeVDainese, Loizides, Paic, EPJC 38 (2005) 461.Same theoretical calculation (SW quenching weights) and similar results in Eskola, Honkanen, Salgado, Wiedemann, NPA747 (2005) 511

    Frankfurt, 07.12.2006 Andrea Dainese

  • Limited sensitivity of RAAStrong suppression requires very large densitySurface emission scenarioRAA determined by geometry rather than by density itself Limited sensitivity to

    Need more differential observables:massive partonsRAA vs reaction planestudy of jet shapes Eskola, Honkanen, Salgado, Wiedemann, NPA 747 (2005) 511.

    Frankfurt, 07.12.2006 Andrea Dainese

  • Lower E loss for heavy quarks ?In vacuum, gluon radiation suppressed at q < mQ/EQ dead cone effect

    Dead cone implies lower energy loss (Dokshitzer-Kharzeev, 2001):energy distribution wdI/dw of radiated gluons suppressed by angle-dependent factorsuppress high-w tailDokshitzer, Khoze, Troyan, JPG 17 (1991) 1602.Dokshitzer and Kharzeev, PLB 519 (2001) 199.

    Frankfurt, 07.12.2006 Andrea Dainese

  • Charm RAA at RHICeffect of the massthermalized componentSmall effect of mass for charm (~50% for D, ~30% for e) at low pT [large uncertainties!]Basically no effect in safe pT-regionArmesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027. (extracted from light-flv hadron data)

    Frankfurt, 07.12.2006 Andrea Dainese

  • Charm + beauty + DY electrons at RHIC(pQCD baseline revised, and its uncertainties)FONLL calculation: Cacciari, Nason, Vogt, PRL95 (2005) 122001Drell-Yan from: Gavin et al., hep-ph/9502372Comparison: Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326FONLL: electron spectrum may be ~50% c + ~50% b for 3 < pT < 8 GeV

    We investigated the DY component: < 10% up to 10 GeV

    Frankfurt, 07.12.2006 Andrea Dainese

  • RAA of c and b electrons at RHICDue to larger mass of b quark electron RAA increased to ~0.4Mass uncertainty (in E loss) and scales uncertainty (in pQCD b/c crossing) were studiedArmesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326,cbc+b

    Frankfurt, 07.12.2006 Andrea Dainese

  • RAA of c and b electrons at RHICOther approaches: include elastic E loss (Djordjevic, Gyulassy, Wicks) collisional dissociation of D/B mesons formed in the medium early after hard scattering (Adil & Vitev)QM06 updatenucl-ex/0611018nucl-ex/0611018(Adil & Vitev)

    Frankfurt, 07.12.2006 Andrea Dainese

  • LayoutHigh-pT (heavy-flavour) particle production in hadronic collisions from pp to AA in factorized QCDpp baseline: pQCD calculationsnuclear effects, in initial and final state

    What have we learnt at Tevatron and RHIC?

    What will be new at the LHC?What do we expect? What should we measure?

    Experimental Perspectives at the LHC

    Frankfurt, 07.12.2006 Andrea Dainese

  • Novelties at LHC (1): Hard ProbesLHC: large hard cross sections!Our set of tools (probes) becomes richer quantitatively:qualitatively: heavy quarks

    g + jet correlations Z0 + jet correlationsLO pQCD by I. Vitev,hep-ph/0212109

    Frankfurt, 07.12.2006 Andrea Dainese

  • Heavy-quark production at the LHCpp: Important test of pQCD in a new energy domainRemember the 15-years saga of b production at Tevatron*

    Baseline predictions: NLO (MNR code) in pp + binary scaling (shadowing included for PDFs in the Pb) ALICE baseline for charm / beauty: Theoretical uncertainty of a factor 23 (next slide)* M.ManganoMNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.

    system :sNN :Pb-Pb (0-5% centr.)5.5 TeVp-Pb (min. bias) 8.8 TeVpp14 TeV4.3 / 0.27.2 / 0.311.2 / 0.5115 / 4.60.8 / 0.030.16 / 0.0070.65 / 0.800.84 / 0.90--

    Frankfurt, 07.12.2006 Andrea Dainese

  • Theoretical Uncertainties(HERA-LHC Workshop)MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.Evaluation of theoretical uncertaintiesbeautycharmCERN/LHCC 2005-014hep-ph/0601164

    Frankfurt, 07.12.2006 Andrea Dainese

  • Model Comparisons(HERA-LHC Workshop)Compare predictions by several different modelsGood agreement between collinear factorization based calculations: FO NLO and FONLLkT factorization (CASCADE) higher at large pTbeautycharmCERN/LHCC 2005-014hep-ph/0601164

    Frankfurt, 07.12.2006 Andrea Dainese

  • Energy extrapolation via pQCD?Different systems (pp, p-Pb, Pb-Pb) will have different s valuesResults in pp at 14 TeV will have to extrapolated to 5.5 TeV (Pb-Pb energy) to compute, e.g., nuclear modification factors RAApQCD: there ratio of results at 14 TeV/5.5 TeV has small uncertaintycharmbeauty12%8%MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.

    Frankfurt, 07.12.2006 Andrea Dainese

  • Novelties at LHC (2): Small xProbe unexplored small-x region with HQs at low pT and/or forward ydown to x~10-4 with charm already at y=0Eskola, Kolhinen, Vogt, PLB582 (2004) 157Gotsmann, Levin, Maor, Naftali, hep-ph/0504040Window on the rich phenomenology of high-density PDFs: gluon saturation / recombination effects

    Possible effect: enhancement of charm production at low pT w.r.t. to standard DGLAP-based predictions, even in pp!

    Frankfurt, 07.12.2006 Andrea Dainese

  • Probing nuclear initial state PDFs with HQsShadowing in pA (AA)CGC in pA (AA)Double parton scattering in pA

    Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61

    Frankfurt, 07.12.2006 Andrea Dainese

  • Probing nuclear initial state PDFs with HQsShadowing 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~1.5-2 GeV > mcFor mT,c~Qs, charm prod. CGC-dominated: scales with Npart in pA (not Ncoll) harder pT spectra, since typical kT~Qs~1.5 GeV, while in standard factorization kT~LQCD~0.2 GeVKharzeev, Tuchin, NPA 735 (2004) 248

    Frankfurt, 07.12.2006 Andrea Dainese

  • Probing nuclear initial state PDFs with HQsShadowing 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

    Frankfurt, 07.12.2006 Andrea Dainese

  • Heavy Quark Energy Loss at LHC~100 cc pairs and ~5 bb pairs per central Pb-Pb collisionExperiments will measure with good precision RAA for D and B, and for their decay leptons (as Ill show in 5)

    What can we learn from a comparative quenching study of massive and massless probes at the LHC?

    Frankfurt, 07.12.2006 Andrea Dainese

  • Heavy Flavour RAA at LHCBaseline: PYTHIA, with EKS98 shadowing, tuned to reproduce c and b pT distributions from NLO pQCD (MNR)(m/E)-dep. E loss withMNR: Mangano, Nason, Ridolfi, NPB 373 (1992) 295.Armesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027. * EKRT Saturation model:Eskola, Kajantie, Ruuskanen, Tuominen, NPB 570 (2000) 379.

    Frankfurt, 07.12.2006 Andrea Dainese

  • Colour-charge and mass dep. of E loss with Heavy-to-Light ratios at LHCHeavy-to-light ratios:Compare g h , c D and b BArmesto, Dainese, Salgado, Wiedemann, PRD71 (