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Heavy Quarks in view of the LHC

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

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Heavy Quarks in view of the LHC

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  1. Heavy Quarks in view of the LHC Andrea Dainese INFN (ALICE Collaboration) Frankfurt, 07.12.2006 Andrea Dainese

  2. PARTON ENERGY LOSS 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 Frankfurt, 07.12.2006 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: factorized pQCD approach Frankfurt, 07.12.2006 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) Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033 Cacciari, Nason, Vogt, PRL95 (2005) 122001 Q  e+X pp  QQ: pQCD calculations vs data • Calculation 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 pT QM06 update later Frankfurt, 07.12.2006 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: Frankfurt, 07.12.2006 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, Peigne‘, Schiff, NPB 483 (1997) 291. Zakharov, JTEPL 63 (1996) 952. Salgado, Wiedemann, PRD 68(2003) 014008. Frankfurt, 07.12.2006 Andrea Dainese

  7. (Quark Matter 05) matches pT-indepence of suppression at high pT Model vs RHIC “light” data • 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 Frankfurt, 07.12.2006 Andrea Dainese

  8. ? large  RAA indep. of Limited sensitivity of RAA • Strong suppression requires very large density • Surface emission scenario • RAA determined by geometry rather than by density itself • Limited sensitivity to • Need more differential observables: • massive partons • RAA vs reaction plane • study of jet shapes • … Eskola, Honkanen, Salgado, Wiedemann, NPA 747 (2005) 511. Frankfurt, 07.12.2006 Andrea Dainese

  9. 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. Frankfurt, 07.12.2006 Andrea Dainese

  10. other contributions become important larger uncertainties Charm RAA at RHIC (extracted from light-flv hadron data) effect of the mass thermalized component Small effect of mass for charm (~50% for D, ~30% for e) at low pT [large uncertainties!] Basically no effect in “safe” pT-region Armesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027. Frankfurt, 07.12.2006 Andrea Dainese

  11. QM06 update QM06 update ? 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 Charm + beauty + DY electrons at RHIC(pQCD baseline revised, and its uncertainties) FONLL: electron spectrum may be ~50% c + ~50% b for 3 < pT < 8 GeV We investigated the DY 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 Frankfurt, 07.12.2006 Andrea Dainese

  12. Theory predicts e RAA (~0.4)larger than p RAA (~0.2) e spectra in principle sensitive to mass hierarchy Perturbative uncertainty on the pp baseline comparable to model-intrinsic uncertainty in determination of Preliminary STAR data not conclusive for comparison with theory Theory predicts e RAA (~0.4)larger than pRAA (~0.2) e spectra in principle sensitive to mass hierarchy Perturbative uncertainty on the pp baseline comparable to model-intrinsic uncertainty in determination of Final data (QM06): electron RAA tends to be overestimated nucl-ex/0611018 QM06 update Djordjevic, Gyulassy, Wicks, nucl-th/0512076 RAA of c and b electrons at RHIC • Due to larger mass of b quark electron RAA increased to ~0.4 • Mass uncertainty (in E loss) and scales uncertainty (in pQCD  b/c crossing) were studied b c+b c Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326, Frankfurt, 07.12.2006 Andrea Dainese

  13. RAA of c and b electrons at RHIC QM06 update • 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) Frankfurt, 07.12.2006 Andrea Dainese

  14. 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 Frankfurt, 07.12.2006 Andrea Dainese

  15. 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 Frankfurt, 07.12.2006 Andrea Dainese

  16. 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 included for PDFs in the Pb) • ALICE baseline for charm / beauty: Theoretical uncertainty of a factor 2—3 (next slide) * M.Mangano MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. Frankfurt, 07.12.2006 Andrea Dainese

  17. 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. Frankfurt, 07.12.2006 Andrea Dainese

  18. Model Comparisons(HERA-LHC Workshop) CERN/LHCC 2005-014 hep-ph/0601164 Compare predictions by several different models charm beauty Good agreement between collinear factorization based calculations: FO NLO and FONLL kT factorization (CASCADE) higher at large pT Frankfurt, 07.12.2006 Andrea Dainese

  19. 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 12% 8% MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. Frankfurt, 07.12.2006 Andrea Dainese

  20. increasing s sc(DGLAP+non-linear) sc(DGLAP) 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 • Possible effect: enhancement of charm production at low pT w.r.t. to standard DGLAP-based predictions, even in pp! Eskola, Kolhinen, Vogt, PLB582 (2004) 157 Gotsmann, Levin, Maor, Naftali, hep-ph/0504040 Frankfurt, 07.12.2006 Andrea Dainese

  21. c c Probing nuclear initial state PDFs with HQs • Shadowing 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

  22. c c Probing nuclear initial state PDFs 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~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 Frankfurt, 07.12.2006 Andrea Dainese

  23. 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 PDFs 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 Frankfurt, 07.12.2006 Andrea Dainese

  24. Heavy Quark Energy Loss at LHC • ~100 cc pairs and ~5 bb pairs per central Pb-Pb collision • Experiments will measure with good precision RAA for D and B, and for their decay leptons (as I’ll 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

  25. 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 • * 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. Frankfurt, 07.12.2006 Andrea Dainese

  26. 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 Frankfurt, 07.12.2006 Andrea Dainese

  27. 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 Frankfurt, 07.12.2006 Andrea Dainese

  28. f = p/2 f = 0 Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326. Azimuthal asymmetry (v2) • Azimuthal asymmetry --v2 or RAA(f)-- 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 • at higher pt: path-length dependence of E loss in almond-shaped medium PHENIX p0 v2 Cole @ Quark Matter 05 v2 from E loss: Dainese, Loizides, Paic, EPJC 38 (2005) 461 Frankfurt, 07.12.2006 Andrea Dainese

  29. 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 Frankfurt, 07.12.2006 Andrea Dainese

  30. CMS ATLAS Experimental study of heavy flavours in AA at the LHC Frankfurt, 07.12.2006 Andrea Dainese

  31. rec. track e Primary Vertex B X d0 Tracking & Vertexing • D mesons ct ~ 100–300 mm, B mesons ct ~ 500 mm • Secondary vertex capabilities! Impact param. resolution! Frankfurt, 07.12.2006 Andrea Dainese

  32. rf: 50 mm z: 425 mm PIXEL CELL Two layers: r = 4 cm r = 7 cm INFN Padova-Legnaro Impact parameter resolution Resolution mainly provided by the layers of silicon pixels  9.8 M Frankfurt, 07.12.2006 Andrea Dainese

  33. acceptance: pt > 0.2 GeV/c rf < 50 mm for pt > 1.5 GeV/c acceptance: pt > 1 GeV/c rf < 50 mm for pt > 2.5 GeV/c B = 0.5 T B = 4 T Dpt/pt < 2% up to 100 GeV/c Dpt/pt < 2.5% up to 20 GeV/c < 6% up to 100 GeV/c Tracking & Vertexing • D mesons ct ~ 100–300 mm, B mesons ct ~ 500 mm • Secondary vertex capabilities! Impact param. resolution! Frankfurt, 07.12.2006 Andrea Dainese

  34. Lepton and Hadron ID • D and B: large B.R. to leptons: ~10% e + ~10% m • ALICE: • electrons: Transition Rad. + dE/dx in |h| < 0.9 and pt > 1 GeV/c + EM cal (performance under study) • muons: -4 <h< -2.5 and pt >1 GeV/c (use pz to punch through abs.) • CMS (ATLAS): • muons: |h| < 2.4 (3) and pt > 3.5 (4) GeV/c • electrons in EM cal? (no heavy-ion studies yet) • With leptons, difficult to measure D(B) pt distr. and go to low pt (loose pt correlation) Exclusive hadronic decay channels (charm)  Need PID (kaons!) to reject huge combin. background in AA • ALICE hadron ID: large TPC + high-res TOF + RICH (small acc.) Frankfurt, 07.12.2006 Andrea Dainese

  35. Invariant mass analysis Charm reconstruction: D0 K-p+ • Large combinatorial background (dNch/dy=6000 in central Pb-Pb!) • Main selection: displaced-vertex selection • pair of opposite-charge tracks with large impact parameters • good pointing of reconstructed D0 momentum to the primary vertex Frankfurt, 07.12.2006 Andrea Dainese

  36. rec. track e Primary Vertex B X d0 Beauty via displaced electrons • ALICE has excellent electron identification capabilities (TRD + TPC) • Displaced electrons from B decays can be tagged by an impact parameter cut Frankfurt, 07.12.2006 Andrea Dainese

  37. electron CMS & ATLAS • should have similar performance, • at least with muons • higher ptmin because more material • & larger field • should have similar performance • higher ptmin because lack of K id Expected pt coverage 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) D0 Kp B  e + X Frankfurt, 07.12.2006 Andrea Dainese

  38. measured at 14 TeV, then scaled by pQCD to 5.5 TeV Calibrating the probe (pp, s = 14 TeV) Expected sensitivity in comparison to pQCD: B  e + X D0 Kp 1 year at nominal luminosity (109 pp events) Frankfurt, 07.12.2006 Andrea Dainese

  39. mb = 4.8 GeV Low pt (< 6–7 GeV/c) Also nuclear shadowing (here EKS98), in-medium hadr… High pt (> 6–7 GeV/c) Only parton energy loss Charm and Beauty E Loss : RAA D0 Kp B  e + X 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) Frankfurt, 07.12.2006 Andrea Dainese

  40. Heavy-to-light ratios in ALICE 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) Frankfurt, 07.12.2006 Andrea Dainese

  41. Beauty via (forward) muons • Muons “identified” in the forward spectrometer (-4 << -2.5)  single muons in the spectrometer: beauty dominates for pt > 2-3 GeV/c inner bars: stat. errors outer bars: syst. errors Pb-Pb 0-5% Frankfurt, 07.12.2006 Andrea Dainese

  42. W’s as a medium-blind reference • pQCD predicts b/W crossing at pTmuon ~ 30 GeV/c • In Pb-Pb, b-quark in-medium energy loss would shift crossing to lower pT Ding, A.D., Zhou, QM06 poster. Conesa, A.D., Ding, Martinez, Zhou, in preparation Frankfurt, 07.12.2006 Andrea Dainese

  43. primary J/y J/y from B J/y from B (à la CDF) in CMS & ALICE J/ym+m- J/y e+e- CMS: CMS/NOTE 2001/008,ALICE: CERN/LHCC 99-13 Frankfurt, 07.12.2006 Andrea Dainese

  44. 265 days to LHC startup! Conclusions • At LHC heavy quarks will be produced with large rates robust tool for the study of QCD in extreme conditions • Heavy-quark phenomelogy promises to be very rich • from very low pT: probe small-x structure of p and nucleus • to very high pT: probe the QCD medium via energy loss • Excellent “heavy-quark busters” (ALICE, ATLAS, CMS) are being installed at CERN Frankfurt, 07.12.2006 Andrea Dainese

  45. Appendix:QUARKONIA at LHC Frankfurt, 07.12.2006 Andrea Dainese

  46. enhanced regeneration enhanced suppression Statistical hadronization: huge enhancements for Xcc, Wcc, Bc, Wccc e.g. 1000 for Wccc/Dfrom pp to Pb-Pb 30 SPS RHIC LHC Becattini, PRL95 (05) 022301 Quarkonia at LHC: y (cc)  H.Satz • J/ suppression & regeneration? • c, y’ suppression (J/ TD ~ 1.5-2 Tc)? Satz, CERN Heavy Ion Forum, 09/06/05 • TLHC >> J/ TD • Wong, PRC 72 (2005) 034906 • Alberico, hep-ph/0507084 Frankfurt, 07.12.2006 Andrea Dainese

  47. RHIC LHC Gunion and Vogt, NPB 492 (1997) 301  production ’/ vs pt sensitive to system temp. & size Vogt, hep-ph/0205330 Quarkonia at LHC:  (bb)  ds/dy @ LHC ~20 x RHIC  H.Satz •  melts only at LHC • ’ TD ~ J/ TD • Wong, PRC 72 (2005) 034906 • Alberico, hep-ph/0507084 • Small  regeneration • Grandchamp et al., hep-ph/0507314 • ’ can unravel J/ suppression vs. regeneration Frankfurt, 07.12.2006 Andrea Dainese

  48. Quarkonia at LHC:experimental challenges • Important contribution to y production from B J/y(y’) + X • ~20% of J/y • ~40% of y’ • Normalization: Drell-Yan not available for normalization (from qq, while quarkonia from gg at LHC; and small cross section at LHC)  W, Z? • Different Q2, x Open heavy flavour, but … • Energy loss? • Thermal charm production?  Possible alternative: RAA (à la PHENIX) Need to measure this! Frankfurt, 07.12.2006 Andrea Dainese

  49. m+m- m+m- m+m- e+e- J/y  J/y  acceptance (%) -4<h<-2.5 -4<h<-2.5 Quarkonia acceptances Frankfurt, 07.12.2006 Andrea Dainese

  50. Charmonia Performance Bkg input: dNch/dy~2500-4000 in central Pb-Pb. for 1 month central central min. bias central Frankfurt, 07.12.2006 Andrea Dainese

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