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ALICE potential for heavy-flavour physics

This presentation discusses the potential for heavy-flavour physics using the ALICE collaboration at LHC, including charm and beauty measurements, expectations, and running conditions. It covers novel aspects of heavy-ion physics at LHC, high-density parton distributions, and probes of the medium using parton energy loss. The ALICE detector's capabilities and ongoing detector installations are also highlighted.

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ALICE potential for heavy-flavour physics

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  1. ALICE potential for heavy-flavour physics Giuseppe E Bruno Università di Bari and INFN – Italy for the ALICE collaboration Incontri di Fisica delle Alte Energie IFAE 2009 - VIII Edizione

  2. ALICE potential for heavy-flavour physics Giuseppe E Bruno Università di Bari and INFN – Italy for the ALICE collaboration Outline Foreword: heavy-ion physics at LHC Charm and Beauty at the LHC Heavy-flavour program in ALICE Measurements in preparation Examples of expected performance Conclusions

  3. Foreword: Heavy-ion Physics • Plenary talks by D’Enterria and Armesto LHC: factor 30 jump in √s w.r.t. RHIC hotter, bigger, longer-livedfireballof QCD matter Giuseppe E. Bruno

  4. Foreword: novel aspects of HI physics at LHC • High-density parton distributions • bulk of partons at xBjorken=pparton/pproton< 10-3 • saturated gluon densities • Color Glass Condensate in the initial state? • Hard processes • significant part of cross section • can be calculated by pQCD • happen at initial state • probe the matter they traverse increasing √s Giuseppe E. Bruno

  5. Foreword: novel aspects of HI physics at LHC • High-density parton distributions • bulk of partons at xBjorken=pparton/pproton< 10-3 • saturated gluon densities • Color Glass Condensate in the initial state? • Hard processes • significant part of cross section • can be calculated by pQCD • happen at initial state • probe the matter they traverse x2000 Giuseppe E. Bruno

  6. LHC • Running conditions: • + other ions (Sn, Kr, O) & energies (e.g.: pp @ 5.5 TeV) *Lmax (ALICE) = 1031 ** Lint (ALICE) ~ 0.5 nb-1/year Giuseppe E. Bruno

  7. factor ~2 uncertainty Heavy Flavour @ LHC • cc and bb rates • NLO predictions (ALICE baseline for charm & beauty) MNR code (FO NLO): Mangano, Nason, Ridolfi, NPB373 (1992) 295. With EKS98 shadowing. beauty charm * M.Mangano Giuseppe E. Bruno

  8. factor ~2 uncertainty Heavy Flavour @ LHC • cc and bb rates • NLO predictions (ALICE baseline for charm & beauty) MNR code (FO NLO): Mangano, Nason, Ridolfi, NPB373 (1992) 295. With EKS98 shadowing. LHC startup at s = 10 TeV (after few days at 0.9 TeV?)  yields lower by 25% * M.Mangano Giuseppe E. Bruno

  9. charm beauty Cartoon The charm of small-x gluons • Probe unexplored small-x region with HQs at low pt and/or forward y s=14 TeV D mesons pt0, y=0 J/ypt0, y4 s=14 TeV x~10-4 x~10-6 • Charm measurements at low-pt or forward y  Window on high-density PDFs phenomenology: gluon saturation / recombination effects / CGC Giuseppe E. Bruno

  10. Charm & beauty as probes • calculable in pQCD; calibration measurement from pp • rather solid ground • caveat: modification of initial state from pp to AA • shadowing ~ 30 % • saturation? • pA reference fundamental! • produced essentially in initial impact • probes of high density phase • no extra production at hadronization • probes of fragmentation • e.g.: independent string fragmentation vs recombination Giuseppe E. Bruno

  11. Probing the medium • Parton Energy Lossby • medium-induced gluon radiation • collisions with medium gluons pred: q: colour triplet u,d,s: m~0, CR=4/3 (difficult to tag at LHC) g: m=0, CR=3 > E loss, dominant at LHC c: m~1.5 GeV, CR=4/3 small m, tagged by D’s b: m~5 GeV, CR=4/3 large mass  dead cone  < E loss g: colour octet Q: colour triplet QCD medium Dokshitzer and Kharzeev, PLB 519 (2001) 199. Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003. Djordjevic, Gyulassy, Horowitz, Wicks, NPA 783 (2007) 493

  12. QCD medium Probing the medium • Parton Energy Lossby • medium-induced gluon radiation • collisions with medium gluons pred: q: colour triplet u,d,s: m~0, CR=4/3 (difficult to tag at LHC) g: m=0, CR=3 > E loss, dominant at LHC c: m~1.5 GeV, CR=4/3 small m, tagged by D’s b: m~5 GeV, CR=4/3 large mass, < E loss g: colour octet Q: colour triplet Real photon: colourless Medium-blind, Control Virtual photon/W: colourless

  13. enhanced regeneration enhanced suppression 30 SPS RHIC LHC Quarkonia at LHC: y (cc) &  (bb) • J/ suppression & regeneration? • c, y’ suppression (J/ TD ~ 1.5-2 Tc)? TLHC >> J/ TD •  melts only at LHC • ’ TD ~ J/ TD • Small  regeneration  ’ can unravel J/  suppression VS regeneration Giuseppe E. Bruno

  14. The ALICE detector • Acceptance: η<|0.9| • (di)electrons: J/, ’, , ’, ’’ open charm & beauty • hadrons: D±, D0, … • Acceptance: -4<η<-2.5 • (di)muons: J/, ’, , ’, ’’ open charm & beauty TOF PID TRD Electron ID TPC Tracking, dE/dx ITS Vertexing, Low pt tracking • electron-muon coincidences: open charm & beauty MUON Spectrometer Physics at LHC - Philippe Pillot Giuseppe E. Bruno 14

  15. ALICE Detector Installation mid 2008 Complete: ITS, TPC, TOF, HMPID, FMD, T0, V0, ZDC, Muon arm, Acorde Partial installation: PHOS (1/5) TRD (4/18) PMD (9/48) EMCAL (0/6) ~ 40% DAQ/HLT ALICE Status Installation targets met by mid 2008 15

  16. ALICE Detector Installation Goal 2009 Shutdown used for additional installation and repairs Complete: ITS, TPC, TOF,HMPID, FMD, T0, V0, ZDC, Muon arm, Acorde PMD,DAQ Partial installation: PHOS(3/5) 6-8/18 TRD 2-4/6 EMCAL ~ 50% HLT ALICE Status Giuseppe E. Bruno Number of TRD & EMCAL modules depends on access conditions during LHC power test !

  17. D0 Kp D+ Kpp Ds KKp D*  D0p D0 Kppp LcpKp TOF (K/p id) under study TPC (tracking) K p ITS (vertexing) Hadronic charm D0 Giuseppe E. Bruno

  18. rf: 50 mm z: 425 mm PIXEL CELL Impact parameter < 50 mm for pt > 1.5 GeV Two layers: r = 4 cm r = 7 cm Impact parameter resolution • d0 = distance of closest approach between track and primary vertex • d0 resolution mainly provided by the two innermost layers of the ITS (pixels) • R=4 and 7 cm, ~107 channels Silicon Pixel Detector BEAM (Z) pixel size 50425 m d0 resolution Giuseppe E. Bruno

  19. Impact parameter < 50 mm for pt > 1.5 GeV Impact parameter resolution • d0 = distance of closest approach between track and primary vertex • d0 resolution mainly provided by the two innermost layers of the ITS (pixels) • R=4 and 7 cm, ~107 channels Silicon Pixel Detector d0 resolution Giuseppe E. Bruno

  20. pair of opposite-charge tracks with large impact parameters • good pointing of reconstructed D momentum to the primary vertex D0 Charm reconstruction: D0 K-p+ • Two vertexing algorithms with full error-matrix treatment • Large combinatorial background (dNch/dy=6000 in Pb-Pb simul.) • Main selection: displaced-vertex selection Giuseppe E. Bruno

  21. pair of opposite-charge tracks with large impact parameters • good pointing of reconstructed D momentum to the primary vertex D0 Charm reconstruction: D0 K-p+ • Two vertexing algorithms with full error-matrix treatment • Large combinatorial background (dNch/dy=6000 in Pb-Pb simul.) • Main selection: displaced-vertex selection Giuseppe E. Bruno

  22. pair of opposite-charge tracks with large impact parameters • good pointing of reconstructed D momentum to the primary vertex D0 Invariant mass analysis Charm reconstruction: D0 K-p+ • Two vertexing algorithms with full error-matrix treatment • Large combinatorial background (dNch/dy=6000 in Pb-Pb simul.) • Main selection: displaced-vertex selection Giuseppe E. Bruno

  23. Charm reconstruction: D0 K-p+ • Two vertexing algorithms with full error-matrix treatment • Large combinatorial background (dNch/dy=6000 in Pb-Pb simul.) • Main selection: displaced-vertex selection

  24. rec. track e Primary Vertex B d0 X Beauty in the barrel: B  e + X • Electron PID (TPC+TRD): reject most of the hadrons • d0 cut: reduce charm and bkg electrons (Dalitz, g conv.) • Subtract (small) residual background (ALICE data + MC)

  25. rec. track e Primary Vertex B d0 X Beauty in the barrel: B  e + X • Electron PID (TPC+TRD): reject most of the hadrons • d0 cut: reduce charm and bkg electrons (Dalitz, g conv.) • Subtract (small) residual background (ALICE data + MC)

  26. rec. track e Primary Vertex B d0 X Beauty in the barrel: B  e + X • Electron PID (TPC+TRD): reject most of the hadrons • d0 cut: reduce charm and bkg electrons (Dalitz, g conv.) • Subtract (small) residual background (ALICE data + MC)

  27. rec. track e Primary Vertex B 1 year at nominal luminosity (31030 cm-2s-1 pp, 51026 cm-2s-1Pb-Pb) (109 pp events, 107 central Pb-Pb events) d0 X electron Beauty in the barrel: B  e + X • Electron PID (TPC+TRD): reject most of the hadrons • d0 cut: reduce charm and bkg electrons (Dalitz, g conv.) • Subtract (small) residual background (ALICE data + MC)

  28. Comparison to pQCD predictions pp, s = 14 TeV charm (D0  Kp) beauty (B  e+X) 1 year at nominal luminosity (31030 cm-2s-1) (109 pp events)

  29. mb = 4.8 GeV Expected performance on D, B RAA • should clarify the heavy flavour quenching mechanism D0 K-p+ B  e + X 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) Giuseppe E. Bruno

  30. Expected performance on D, B RAA mass dependence colour charge dependence • should clarify the heavy flavour quenching mechanism 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) Giuseppe E. Bruno

  31. More beauty in the barrel:displaced J/yee & b-tagged jets under study Displaced di-electrons (TPC,TRD) from J/y from B decays tagged by and impact parameter cut (ITS). Standard method for B cross section measurement at Tevatron First approach to b-tagging: Reconstructed jets (TPC, EMCAL) with ≥3 tracks displaced from the primary vertex (ITS) Pseudoproper decay time (pt>0) Single-track impact parameter significance d0/sd0 total background all J/y J/y from B

  32. ALICE’s forward muons • Muons “identified” in the spectrometer (-4 << -2.5) Pb-Pb 0-5% 5.5 TeV: single muon statistics for 1 month at nominal lumi (4 x 108 events) ALICE muon spectrometer acc.: -4 < h < -2.5, pt > 1 GeV, p > 4 GeV c dominates for 1 < pt < 3 GeV/c Wm (medium-blind reference) dominates for pt > 25 GeV/c b dominates for 3 < pt < 25 GeV/c

  33. Beauty via muons in pp and Pb-Pb • MC-baseddeconvolution procedure dsm/dpt dsB/dptmin • Large pt reach: ~80% of the total beauty cross-section is reconstructed • (Very) small statistical error, systematics ~10-15% • Works in pp & AA collisions ( RAA) pp Pb-Pb (0-5%) • single-m • mm single-m bars: stat. errors boxes: syst. errors inner bars: stat. errors outer bars: syst. errors pp: 1 month at reduced luminosity (1030 cm-2s-1, 7 x 1010 pp events) Pb-Pb: 1 month at nominal luminosity (4 x 108 central Pb-Pb events)

  34. ITS (vertexing) TPC (tracking) TRD (e/p id) e e m m MUON (tracking,id) Quarkonia • Measured both in the di-electron (midrapidity, TRD) and di-muon (forward rapidity, MUON) channel Giuseppe E. Bruno

  35. Quarkonia Performance Bkg input: dNch/dy=4000 in central Pb-Pb. for 1 month

  36. Summary • LHC: heavy quarks and quarkonia 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 • Charmonia & bottomonia as probes of QCD phase transition • ALICE in excellent position: • dedicated detectors • promising performance for all key measurements Giuseppe E. Bruno

  37. Thank you First interaction in ALICE: 11.9.2008 (beam – pixel collisions) Giuseppe E. Bruno

  38. Probing the medium • quenching vs colour charge • heavy flavour from quark (CR = 4/3) jets • light flavour from (pT-dep) mix of quark and gluon (CR = 3) jets • quenching vs mass • heavy flavour predicted to suffer less energy loss • gluonstrahlung • collisional loss • beauty vs charm Giuseppe E. Bruno

  39. rec. track ITS (vertexing) TPC (tracking + e/p id) TRD (e/p id) e e Primary Vertex B X d0 Beauty from single electrons Be+X Giuseppe E. Bruno

  40. S per 107 central Pb-Pb events S/(S+B) Error composition stat  syst error stat error 11% from overall normalization not included Beauty in the barrel: displaced e’s • Expected ALICE performance (1 month Pb-Pb) • e± identification from TRD and dE/dx in TPC • impact parameter from ITS Giuseppe E. Bruno

  41. v2 of c and b • Expected uncertainties on D+ (Kpp) and electrons from B • Best sensitivity at intermediate pt: 3 – 7 GeV/c  charm and beauty thermalization in the medium (recombination models) D+ Kpp B  e 2107 min.bias Pb-Pb events D+ v2 calc. from Ko et al. b ele v2 from van Hees et al. + Armesto et al.

  42. TRD (e/p id) TPC (tracking + e/p id) e+ e- ITS (vertexing) y e+ e- J/y X B x Beauty from displaced J/y BJ/y+X e-e+ Giuseppe E. Bruno

  43. 109 pp events 350 tot 300 Events/10 MeV Events/10 MeV 250 J/y 200 bkg 150 100 50 2.8 2.9 3.0 3.1 3.2 m(e+,e-) [GeV] Beauty in the barrel: displaced J/ye-e+ • Analysis based on a simultaneous fit of • the invariant mass spectrum Giuseppe E. Bruno

  44. 102 Entries/100mm 10 102 1 Entries/100mm 2<pT<3 Gev 10 -2000 -1000 0 1000 2000 3000 x [mm] 1 -2000 -1000 0 1000 2000 3000 x [mm] 109 pp events J/y from B tot J/y ALICE bkg sum pT>0 pT>5 Gev 103 102 Entries/100mm 10 CDF 1 -2000 -1000 0 1000 2000 3000 x [mm] Beauty in the barrel: displaced J/ye-e+ • Analysis based on a simultaneous fit of • the invariant mass spectrum • an “impact parameter” to separate prompt from detached J/y, e.g. pseudo- proper decay time (à la CDF) D.Acosta et al Phys. Rev. D 71 (2005) 032001 • This measurements can allow a determination of the dsbb/dpt cross-section down to pt≈0 Giuseppe E. Bruno

  45. Muons from charm at forward rapidity:without dca cut • Unfold single muon pt and dimuon invariant mass spectra • No dca cuts  use large statistics to constrain the fits pp, single muon pt pp 2.5<h<4, pt > 3 GeV/c  x ~ 10-5 pp, di-muon invariant mass 1 month at reduced luminosity (1030 cm-2s-1, 7 x 1010 pp events)

  46. Muons from charm at forward rapidity:with dca cut under study Decay probability for primary muons 1-exp(-D/ct); D=distance of IP from absorber, which varies with IP position. Secondaries can be reduced through cut on DCA

  47. Many other channels • charm: exclusive hadronic channels • D0  K (tested in pp & PbPb) • D+  K (tested in pp & PbPb) • D±s  KK (under study) • D*  D0 (under study) • D0  K (under study) • c  pK (under study) • charm & bottom: semi-inclusive leptonic channels • c  l + X (à la CDF & D0) • b  l + X (à la CDF & D0) • b  J/ + X (à la CDF & D0) • bbbar  J/ + l (under study) • bbbar  3 (should work in pp) • bbbar  l+l-,l-l+ (Bchain & BBdiff) • bbbar  l-l-,l+l+ (Bchain & B osc.) Giuseppe E. Bruno

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