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Heavy Quarks at the LHC

Heavy Quarks at the LHC. Andrea Dainese INFN Legnaro (ALICE Collaboration). Layout. Heavy-flavour production in hadronic collisions pp baseline: pQCD calculations nuclear effects, in initial and final state What have we learnt at Tevatron and RHIC? What will be new at the LHC?

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Heavy Quarks at the LHC

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  1. Heavy Quarks at the LHC Andrea Dainese INFN Legnaro (ALICE Collaboration) High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  2. Layout • Heavy-flavour production in hadronic collisions • pp baseline: pQCD calculations • nuclear 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 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  3. D s /2 x1 Q2 c x2 s /2 c D • FF: • non-perturbative • phenomenolgy • + fit to data (e+e-) • PDF: • Q2 evolution calculated in pQCD • initial condition from data (HERA) calculable as perturbative series of strong coupling as(mR) Heavy-flavour production: pp proton-proton collisions: factorised pQCD approach High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  4. B production at Tevatron (1.96 TeV) is well described by FONLL Charm production slightly underpredicted at Tevatron (1.96 TeV) CDF, PRL91 (2003) 241804 FONLL: Cacciari, Nason & at RHIC (200 GeV) FONLL: Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033 Cacciari, Nason, Vogt, PRL95 (2005) 122001 Q  e+X pp  QQ+X: pQCD calculations vs data • Calculation of partonic cross section • classic: Fixed Order (NLO) Massive (e.g. MNR code) • state-of-the-art: Fixed Order Next-to-Leading Log (FONLL)  more accurate at high pT latest update in the following High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  5. D c c D c kLkT • initial-state effects: • PDF shadowing • kT broadening (‘Cronin’) D A Cronin enhancement RAB medium formed in the collision • final-state effects • energy loss? [next slide] • in-medium hadronization • (recombination?) A u D 1 c pT ~2-4 GeV/c fgPb / fgp recombination: pH = S pq Q2 = 5 GeV2  baryon/meson enhancement LHCRHICSPS RAA<1~1>1 fragmentation: pH = z pq x Heavy-flavour production: AA Binary scaling for hard yields: A A Binary scaling is “broken” by: High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  6. path length L w kT l Calculating Parton Energy Loss BDMPS-Z formalism transport coefficient Radiated-gluon energy distrib.: (BDMPS case) Casimir coupling factor: 4/3 for q, 3 for g sets the scale of the radiated energy related to constraint kT <w, controls shape at w << wc Baier, Dokshitzer, Mueller, Peigné, Schiff, NPB 483 (1997) 291. Zakharov, JTEPL 63 (1996) 952. Salgado, Wiedemann, PRD 68(2003) 014008. High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  7. (Quark Matter 05) matches pT-indepence of suppression at high pT Models vs RHIC “light” data PRL101 (2008) 232301 • Model: pQCD + E loss probability + detailed collision geometry • Density ( ) “tuned” to match RAA in central Au-Au at 200 GeV Dainese, Loizides, Paic, EPJC 38 (2005) 461. Same theoretical calculation (SW quenching weights) and similar results in Eskola, Honkanen, Salgado, Wiedemann, NPA747 (2005) 511 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  8. Gluonsstrahlung probability Dokshitzer Q Detailed massive calculation confirms this qualitative feature R = 105 (Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003) 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 factor • suppress high-w tail Dokshitzer, Khoze, Troyan, JPG 17 (1991) 1602. Dokshitzer and Kharzeev, PLB 519 (2001) 199. High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  9. QM06 QM06 ? Large uncertainty on b/c crossing point in pT: from scales/masses variation it changes from 3 to 9 GeV PHENIX hep-ex/0508034 PHENIX, hep-ex/0609010 PHENIX electron cross section in pp now quite OK also at high pT Heavy-flavour electrons at RHIC(pp baseline) FONLL: electron spectrum may be ~50% c + ~50% b for 3 < pT < 8 GeV Drell-Yan component? < 10% up to 10 GeV FONLL calculation: Cacciari, Nason, Vogt, PRL95 (2005) 122001 Drell-Yan from: Gavin et al., hep-ph/9502372 Comparison: Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  10. STARPhys. Rev. Lett. 98 (2007) 192301 PHENIX Phys.Rev.Lett.98 (2007) 172301 PRL 98, 172301 (2007) e± from heavy flavor Djordjevic, Gyulassy, Wicks, nucl-th/0512076 RAA of c and b electrons at RHIC • Due to large mass of b quark, theory: electron RAA~0.4 • Final data: electron RAA ~ pion RAA ~0.2 at high pT b c+b c Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326, High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  11. RAA of c and b electrons at RHIC • Similar results from recent multi-observable c2-analysis including hydro evolution c+b c only C. Salgado, CERN Heavy Ion Forum, Dec 08 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  12. RAA of c and b electrons at RHIC QM06 • Other approaches: • include elastic E loss (Djordjevic, Gyulassy, Wicks) • collisional dissociation of D/B mesons formed in the medium early after hard scattering (Adil & Vitev) nucl-ex/0611018 nucl-ex/0611018 (Adil & Vitev) High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  13. What have we learnt from Tevatron and RHIC? OK? what if we find the same in pp@14TeV? how do we get a realible reference for PbPb@5.5TeV? CDF, PRL91 (2003) 241804 FONLL: Cacciari, Nason • Tevatron: c and b production relatively well understood • (b better than c...) • theory: leading log resummation (FONLL); parton shower matched to NLO (MC@NLO); accurate treatment of fragmentation (Cacciari et al.: matching of pert. shat and non-pert. fragm. from ee to pp) • experiment: exclusive (or less inclusive) is better (D mesons, BJ/y+X), publish what you measure (not only extrapolations) High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese 13

  14. What have we learnt from Tevatron and RHIC? PHENIX, hep-ex/0609010 b c+b CDF, PRL91 (2003) 241804 FONLL: Cacciari, Nason c • RHIC: heavy-quark (non-phot.) electrons as suppressed as pions, and they do flow (v2, see later) • but the picture is not clear... • pp baseline at upper limit of FONLL band (like CDF’s charm) • suppression not understood (small b contribution? large b E loss?) • Need for dedicated detectors (Si trackers)  RHIC-II, LHC High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese 14

  15. Layout • High-pT (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 • 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 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  16. Novelties at LHC (1): Hard Probes • LHC: large hard cross sections! • Our set of “tools” (probes) becomes richer quantitatively: • qualitatively: • heavy quarks • g + jet correlations • Z0 + jet correlations LO pQCD by I. Vitev, hep-ph/0212109 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  17. LHC startup at s = 10 TeV? • yields lower by 25% Heavy-quark production at the LHC • pp: Important test of pQCD in a new energy domain • Remember the “15-years saga of b production at Tevatron”* • Baseline predictions: NLO (MNR code) in pp + binary scaling (shadowing [EKS98] included for PDFs in the Pb) • e.g. ALICE baseline for charm / beauty: Theoretical uncertainty of a factor 2—3 (next slide) * M.Mangano MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  18. Theoretical Uncertainties(HERA-LHC Workshop) CERN/LHCC 2005-014 hep-ph/0601164 Evaluation of theoretical uncertainties charm beauty MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  19. Model Comparisons(HERA-LHC Workshop) CERN/LHCC 2005-014 hep-ph/0601164 + updates (R.Guernane) Compare predictions by several different models charm beauty General agreement between collinear factorisation based calculations: FO NLO, FONLL, POWHEG, MC@NLO problem with POWHEG charm? kT factorization (LO MC CASCADE) higher at large pT VFNS lower at high pT High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  20. Energy extrapolation via pQCD? • Different systems (pp, p-Pb, Pb-Pb) will have different s values • Results in pp at 14 TeV will have to extrapolated to 5.5 TeV (Pb-Pb energy) to compute, e.g., nuclear modification factors RAA • pQCD: there ratio of results at 14 TeV/5.5 TeV has ‘small’ uncertainty beauty charm Need to define a strategy! Anyway, difficult to have pp reference at 5.5 TeV (only 1 month  limited stats, pT reach) 12% 8% MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  21. increasing s Novelties at LHC (2): Small x • 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 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  22. Probing small-x gluons with HQs (pp) • Large pQCD uncertainties for charm pT0 • onset of saturation ? • Two attempts to include non-linear terms in evolution equations • DGLAP+GLRMQ • BK indicate charm as a sensitive probe in pp Eskola et al., NPB660 (2003) 211 Kutak, Kwiecinski, Martin, Stasto sc(DGLAP+non-linear) sc(DGLAP) |y| < 1 DGLAP: Charm enhancement due to non-linear effects (GLR-MQ term) BK: Charm suppression due to non-linear effects High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  23. c c Probing small-x gluons with HQs (nuclei) • Shadowing in pA (AA) • CGC in pA (AA) • Double parton scattering in pA Effect of shadowing on D meson nuclear modification factors at LHC: RAB(pT0) ~ RGA*RGB at x ~ 2mc/√s ~ 10-3, Q2 ~ 4mc2 ~ 9 GeV2 EKS98:  0.55 for Pb-Pb at 5.5 TeV  0.75 for p-Pb at 8.8 TeV EKS98: Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  24. c c Probing small-x gluons with HQs (nuclei) • Shadowing in pA (AA) • CGC in pA (AA) • Double parton scattering in pA • Effect of shadowing on D meson nuclear modification factors at LHC: • RAB(pT0) ~ RGA*RGB at x ~ 2mc/√s ~ 10-3, Q2 ~ 4mc2 ~ 9 GeV2 • EKS98: •  0.55 for Pb-Pb at 5.5 TeV • 0.75 for p-Pb at 8.8 TeV • EPS08: •  0.4 for Pb-Pb at 5.5 TeV •  0.6 for p-Pb at 8.8 TeV to be computed rigorously, including pT dependence EPS08: Eskola, Paukkunen, Salgado, JHEP0807 (2008) 102 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  25. c c CGC: very similar RpA for p, D, B, ~indep. of pT and rapidity Probing small-x gluons with HQs (nuclei) • 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~1.5-2 GeV > mc • For 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 GeV Kharzeev, Tuchin, NPA 735 (2004) 248 + LHC Predictions Workshop High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  26. 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 small-x gluons with HQs (nuclei) • 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-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  27. Heavy Quark Energy Loss at LHC • ~100 cc pairs and ~5 bb pairs per central Pb-Pb collision • Experiments, with high precision trackers, will measure RAA for D and B, or for their decay leptons What can we learn from a comparative quenching study of massive and massless probes at the LHC? High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  28. Heavy Flavour RAA at LHC • Baseline: PYTHIA, with EKS98 shadowing, tuned to reproduce c and b pT distributions from NLO pQCD (MNR) • (m/E)-dep. E loss with (EKS98) (EKS98) EPS08 (guess) EPS08 (guess) • * EKRT Saturation model: Eskola, Kajantie, Ruuskanen, Tuominen, NPB 570 (2000) 379. Armesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027. MNR: Mangano, Nason, Ridolfi, NPB 373 (1992) 295. High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  29. mass effect For 10 < pT < 20 GeV, charm behaves like a m=0 quark, light-flv hadrons come mainly from gluons RD/h enhancement probes colour-charge dep. of E loss RB/h enhancement probes mass dep. of E loss Colour-charge and mass dep. of E loss with Heavy-to-Light ratios at LHC Heavy-to-light ratios: Compare g  h , c  D and b  B Armesto, Dainese, Salgado, Wiedemann, PRD71 (2005) 054027 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  30. LHC: Beauty-to-Charm ratio RB/D • Compare c and b: same colour charge • Mass effect  Enhancement of factor ~2, independent of (for ) Adapted from Armesto, Dainese, Salgado, Wiedemann, PRD71 (2005) 054027 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  31. medium-sensitive and medium-blind probe in same measurement Beauty energy loss:W-decay muons as a reference single m RCP(pT) early measurement for all experiments at the LHC! Conesa del Valle, Dainese, Ding, Martinez, Zhou, PLB663 (2008) 202 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  32. Other predictions for RAA at LHC D and B meson formation and dissociation inside the medium Radiative+Collisional E loss à la GLV D B D+B similar to prediction from Armesto et al. Wicks, Gyulassy, “Last Call for LHC Predictions” worksho, 2007 Vitev, Adil, “Last Call for LHC Predictions” workshop, 2007 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  33. Charm in-medium hadronization: probe of QGP properties? • Yields of charm hadrons within statistical hadronization model (PYTHIA: 6.92!) PYTHIA: 0.19 0.13 Ratio D/Ds as a probe of T at measured s/S Braun-Muntzinger, Stachel, LHC Predictions Workshop 07 Rafelski, Kuznetsova, LHC Predictions Workshop 07 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  34. Azimuth. asymmetry: v2 from flow • v2 of D and B mesons in non-central collisions tests: • at low/moderate pT: recombination scenario, flow of c/b quarks (?), hence degree of thermalization of medium • Model: • mult. scattering in expanding QGP ( elliptic flow) • hadronization via coalescence + fragmentation c: 15-20% b: 5% van Heese, Rapp, Greco, LHC Predictions Workshop 07 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  35. Azimuth. asymmetry: v2 from E loss • v2 of D and B mesons in non-central collisions tests • at higher pT: path-length dependence of E loss in almond-shaped medium • Model: • Radiative E loss (BDMPS) c: 5-10% RHIC LHC Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326 + LHC Predictions Workshop 07 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  36. Layout • High-pT (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 • 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 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  37. Heavy flavour capabilities:tracking, vertexing, lepton ID primary vertex track d0 High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  38. Heavy-flavour capabilities:acceptances & tracking resolutions HERA-LHC Workshop CERN/LHCC 2005-014 hep-ph/0601164 A.Dainese (ALICE) M.Smizanska (ATLAS) C.Weiser (CMS) U.Uwer (LHCb) High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  39. D0 Kp • D+ Kpp Ds KKp D*  D0p D0 Kpr LcpKp under study • B  e+X • B m+X B5 pr. BJ/yee under study Open heavy-flavour in ALICE D0Kp in Pb-Pb D+Kpp in pp Be +X in Pb-Pb High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  40. probes colour-charge dep. of QCD energy loss probes mass dep. of QCD energy loss Heavy-to-light ratios in ALICE E loss calc.: Armesto, et al. Predictions also by Wicks, et al. 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  41. Summary Stray particle from LHC beam2 interacts in ALICE pixels [Sept 11, 08] • LHC: heavy quarks factory! • Heavy quarks as probes of high-density QCD • low pT: probe small-x structure of p and nucleus • intermediate pT: probe medium thermalisation (reco/flow) • high pT: probe medium density via energy loss • pPb reference needed • can we live without pp at the Pb-Pb energy? • Experiments getting ready • all crucial detectors (Si trackers, lepton ID) already commissioned • thorough calibration and alignment with cosmic runs High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  42. 442 days to LHC startup! Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese First pp@LHC in ~3 months! Hard Probes 2008 14.06.08 Andrea Dainese First pp collisions within days! ISMD 2008, DESY Hamburg, 18.09.08 Andrea Dainese High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  43. after all, maybe we don’t care too much about the LHC starting ... High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  44. EXTRA SLIDES High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  45. 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-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  46. pair of opposite-charge tracks with large impact parameters • good pointing of reconstructed D momentum to the primary vertex • large distance (dPS) between primary and secondary vertex • good pointing of reconstructed D momentum to the primary vertex D0 D+ Invariant mass analysis 50 40 30 D0 D+ 20 10 1 year at nominal luminosity (109 pp events, 107 central Pb-Pb events) Charm reconstruction: D0 K-p+ & D+ K-p+p+ • Two vertexing algos with full error-matrix treatment • Large combinatorial background (dNch/dy=6000 in Pb-Pb simul.) • Main selection: displaced-vertex selection High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  47. electron rec. track e Primary Vertex B X d0 Beauty in the barrel:displaced single electrons • ALICE has excellent electron identification capabilities (TRD + TPC) • Displaced electrons from B decays can be tagged by an impact parameter cut High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

  48. Lxy Beauty in the barrel:displaced J/yee in progress • Standard method for b prod. meas. at the Tevatron • Displaced di-electrons (TPC,TRD) from J/y from B decays tagged by an impact parameter cut (ITS) J/y pseudoproper decay time (pt>0) total background all J/y J/y from B High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese

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