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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) Prague, 07.11.2007 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 Prague, 07.11.2007 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 Prague, 07.11.2007 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 Prague, 07.11.2007 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: Prague, 07.11.2007 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. Prague, 07.11.2007 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 Prague, 07.11.2007 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. Prague, 07.11.2007 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. Prague, 07.11.2007 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. Prague, 07.11.2007 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 Prague, 07.11.2007 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 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, Prague, 07.11.2007 Andrea Dainese

  13. 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) Prague, 07.11.2007 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 Prague, 07.11.2007 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 Prague, 07.11.2007 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. Prague, 07.11.2007 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. Prague, 07.11.2007 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 Prague, 07.11.2007 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. Prague, 07.11.2007 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 Prague, 07.11.2007 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 Prague, 07.11.2007 Andrea Dainese

  22. c c CGC: very similar RpA for p, D, B, ~indep. of pt and rapidity 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 + LHC Predictions Workshop Prague, 07.11.2007 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 Prague, 07.11.2007 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? Prague, 07.11.2007 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. Prague, 07.11.2007 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 Prague, 07.11.2007 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 Prague, 07.11.2007 Andrea Dainese

  28. b Energy loss:Use 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, in preparation Prague, 07.11.2007 Andrea Dainese

  29. “American” 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 Wicks, Gyulassy, “Last Call for LHC Predictions” workshop Vitev, Adil, “Last Call for LHC Predictions” workshop Prague, 07.11.2007 Andrea Dainese

  30. Charm hadron ratios as 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 Rafelski, Kuznetsova, LHC Predictions Workshop Prague, 07.11.2007 Andrea Dainese

  31. 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 Prague, 07.11.2007 Andrea Dainese

  32. 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) RHIC LHC c: 5-10% Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326 + LHC Predictions Workshop Prague, 07.11.2007 Andrea Dainese

  33. 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 Prague, 07.11.2007 Andrea Dainese

  34. CMS ATLAS Experimental study of heavy flavours in AA at the LHC Prague, 07.11.2007 Andrea Dainese

  35. The ALICE Detector Size: 16 x 26 meters Weight: 10,000 tons |h| < 0.9, B = 0.5 T TPC + silicon tracker g,e, p, K, p identification -4 < h < -2.5 muons ALICE Collaboration: >1000 people, 30 countries, ~ 90 Institutes Prague, 07.11.2007 Andrea Dainese

  36. Getting Ready for Beam! • Ready to move MUON arm: largest dipole ever TPC (largest ever) installed, ITS moving in Prague, 07.11.2007 Andrea Dainese

  37. D0 Kp D+ Kpp Ds KKp D*  D0p D0 Kpr LcpKp • D0 Kp D+ Kpp Ds KKp D*  D0p D0 Kpr LcpKp • D0 Kp D+ Kpp Ds KKp D*  D0p D0 Kpr LcpKp TOF (K/p id) under study under study under study TPC (tracking) ITS (vertexing) TPC (tracking) m K p MUON (tracking,id) • B  e+X B5 pr. BJ/yee • B  e+X B5 pr. BJ/yee ITS (vertexing) under study under study • B m+X ITS (vertexing) TPC (tracking e/p id) TRD (e/p id) e Open charm and beauty Prague, 07.11.2007 Andrea Dainese

  38. 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 Prague, 07.11.2007 Andrea Dainese

  39. 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 Prague, 07.11.2007 Andrea Dainese

  40. 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 Prague, 07.11.2007 Andrea Dainese

  41. J/y pseudoproper decay time (pt>5GeV) J/y e+e- primary secondary Beauty in the barrel:multi-prong vertices, displaced J/yee • Beauty decays in many (4-6) charged particles • At the LHC, 20% of J/y from B decays • measurement of b cross section • Displaced di-electrons from J/y from B decays Prague, 07.11.2007 Andrea Dainese

  42. 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% Prague, 07.11.2007 Andrea Dainese

  43. 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) Prague, 07.11.2007 Andrea Dainese

  44. Charm and Beauty E Loss : RAA D0 Kp D+ Kpp B  e + X mC = 1.2 GeV mC = 0 B  e E loss calc.: Armesto, Dainese, Salgado, Wiedemann mb = 4.8 GeV 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) Prague, 07.11.2007 Andrea Dainese

  45. probes colour-charge dep. of QCD energy loss probes mass dep. of QCD energy loss Heavy-to-light ratios E loss calc.: Armesto, Dainese, Salgado, Wiedemann 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) Prague, 07.11.2007 Andrea Dainese

  46. Charm v2: D+ example • First estimate of statistical errors on D+ v2: • best sensitivity at intermediate pt: 3 – 7 GeV/c  charm recombination • Under study: performance with D0 + D+ 2107 min.bias evts 2107 6<b<9 fm evts v2 calc. from Ko et al. Prague, 07.11.2007 Andrea Dainese

  47. Conclusions • LHC: heavy quarks factory! • Heavy quarks as probes of QCD in extreme conditions • 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 • ALICE in excellent position: • dedicated detectors (ITS, TRD, MUON) • promising performance for all key measurements Prague, 07.11.2007 Andrea Dainese

  48. Appendix:QUARKONIA at LHC Prague, 07.11.2007 Andrea Dainese

  49. 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 Prague, 07.11.2007 Andrea Dainese

  50. 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 •  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 Prague, 07.11.2007 Andrea Dainese

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