1. 1 FA - HIM, Seoul - 18 April 2007 Heavy Flavours and Heavy-Ion Collisions: Status and ALICE Perspectives Federico Antinori INFN Padova & CERN

2. FA - HIM, Seoul - 18 April 2007 2Contents Heavy Flavours as medium probes in AA collisions Heavy Flavours as medium probes in AA collisionsdecays production in QCD in p/  -A fragmentation at Tevatron in AA in ALICE

3. 3 FA - HIM, Seoul - 18 April 2007 Intro: Heavy Flavours as medium probes in AA collisions

4. FA - HIM, Seoul - 18 April 2007 4 Charm & beauty: ideal probes calculable in pQCD; calibration measurement from pp calculable in pQCD; calibration measurement from pp  rather solid ground caveat: modification of initial state effects from pp to AA caveat: modification of initial state effects from pp to AA shadowing ~ 30 % shadowing ~ 30 % saturation? saturation? pA reference fundamental! pA reference fundamental! produced essentially in initial impact produced essentially in initial impact  probes of high density phase no extra production at hadronization no extra production at hadronization  probes of fragmentation e.g.: independent string fragmentation vs recombination e.g.: independent string fragmentation vs recombination

5. FA - HIM, Seoul - 18 April 2007 5 Heavy Flavour Quenching quenching vs colour charge quenching vs colour charge heavy flavour from quark (C R = 4/3) jets heavy flavour from quark (C R = 4/3) jets light flavour from (p T -dep) mix of quark and gluon (C R = 3) jets light flavour from (p T -dep) mix of quark and gluon (C R = 3) jets quenching vs mass quenching vs mass heavy flavour predicted to suffer less energy loss heavy flavour predicted to suffer less energy loss gluonstrahlung: dead-cone effect gluonstrahlung: dead-cone effect beauty vs charm beauty vs charm  heavy flavour should provide a fundamental tool to investigate the properties of the medium formed in heavy- ion collisions  at LHC: high stats and fully developed jets

6. 6 FA - HIM, Seoul - 18 April 2007 Heavy Flavour Decays

7. FA - HIM, Seoul - 18 April 2007 7 Some zoology... Lower mass heavy flavour hadrons decay weakly Lower mass heavy flavour hadrons decay weakly  ~ ps  ~ ps c  ~ 100’s µm c  ~ 100’s µm weakly decaying states from PDG 2006 summary tables: weakly decaying states from PDG 2006 summary tables:

8. FA - HIM, Seoul - 18 April 2007 8 Impact parameter ~ c  In UR limit b ~ Lorentz invariant: In UR limit b ~ Lorentz invariant:... so b ~ independent of  if cos  CM distribution is flat: if cos  CM distribution is flat: so, in space, in projection: in projection:so: primary vertex decay vertex decay length = L impact parameter = b  yx d  b

9. FA - HIM, Seoul - 18 April 2007 9 Weak decays of charm typically: typically:  large branching ratio to kaons: D + : D + : D +  K - +X BR ~ 28 % D +  K - +X BR ~ 28 % “golden” channel: D +  K -  +  + BR ~ 9% “golden” channel: D +  K -  +  + BR ~ 9% D 0 : D 0 : D 0  K - +X BR ~ 50% D 0  K - +X BR ~ 50% “golden” channels: D 0  K -  + BR ~ 4% ; D 0  K -  +  +  - BR ~ 7% “golden” channels: D 0  K -  + BR ~ 4% ; D 0  K -  +  +  - BR ~ 7% W ± branchings: W ± branchings:  large semileptonic branching ratio, varies with heavy flavour particle, typical ~ 10% ~ 10% heavy flavour hadrons give in final state an e ± (and ~ 10% a µ ± ) (and with a respectable p T...) cs’ W+W+W+W+ cs’ W+W+W+W+ u d’ e+e+e+e+ e µ+µ+µ+µ+ µ bc W-W-W-W- (similarly: ) C = “Cabibbo angle” C = “Cabibbo angle”

10. FA - HIM, Seoul - 18 April 2007 10 Experimental tools Silicon vertex detectors: Silicon vertex detectors: so: tracks from heavy flavour weak decays typically “miss” primary vertex by ct ~ 100’s µm so: tracks from heavy flavour weak decays typically “miss” primary vertex by ct ~ 100’s µm impact parameter res. of typical heavy flavour apparatus ~ 10’s µm impact parameter res. of typical heavy flavour apparatus ~ 10’s µm e ± and/or µ ± identification e ± and/or µ ± identification charged kaon identification charged kaon identification primary vertex decay vertex decay length = L impact parameter = b  WA92: Si µstrips [Adamovich et al.: NIM A 379 (1996) 252]

11. 11 FA - HIM, Seoul - 18 April 2007 Heavy Flavour Production in QCD

12. FA - HIM, Seoul - 18 April 2007 12 Heavy Flavour hadro-production in pQCD Factorization: Factorization: hadron hadroncharmedhadron cross-section at parton level e.g.: parton distribution functions x a = momentum fraction of parton a in hadron A fragmentation z = fraction of c momentum to hadron D cross-section at hadron level a=q b=q Q Q (at sufficiently large Q 2 )

13. FA - HIM, Seoul - 18 April 2007 13 factorization implies: factorization implies: PDFs can be measured with one reaction... PDFs can be measured with one reaction... say: Drell-Yan: A+B  e + e - + X say: Drell-Yan: A+B  e + e - + X... and used to calculate a different one say: heavy-flavour production say: heavy-flavour production fragmentation independent of the reaction (e.g.: same in pp, e + e - ) fragmentation independent of the reaction (e.g.: same in pp, e + e - )

14. FA - HIM, Seoul - 18 April 2007 14 Leading-order (LO) Relevant diagrams: pair creation Relevant diagrams: pair creation qq  QQ (quark-antiquark annihilation) qq  QQ (quark-antiquark annihilation) gg  QQ (gluon-gluon fusion) gg  QQ (gluon-gluon fusion) q q Q Q Q Q g g Q Q g g Q Q g g

15. FA - HIM, Seoul - 18 April 2007 15 A few results the partonic cross-section decreases with energy the partonic cross-section decreases with energy faster for qq than for gg (which therefore is expected to dominate, except near threshold) faster for qq than for gg (which therefore is expected to dominate, except near threshold) the parton luminosities near threshold increase with energy, the parton luminosities near threshold increase with energy, the cross section increases with the energy of the hadron-hadron collision the pair cross section is proportional to: the pair cross section is proportional to: y (y): rapidity of Q (Q)  Q and Q therefore expected to be close in y  Experimentally: EHS, 360 GeV  - p  DDX [EHS: PLB 123 (1983) 98]

16. FA - HIM, Seoul - 18 April 2007 16 Next-To-Leading-Order (NTLO) in absolute value, LO cross sections are typically underestimated by factor 2.5 - 3 (“K factor”) in absolute value, LO cross sections are typically underestimated by factor 2.5 - 3 (“K factor”) at NTLO: additional diagrams, such as: at NTLO: additional diagrams, such as: Q Q Q Q Q Q higher order corrections to pair creation flavour excitation gluon splitting

17. FA - HIM, Seoul - 18 April 2007 17 the agreement with experiment for the total cross-section is good (within large bands...) the agreement with experiment for the total cross-section is good (within large bands...) e.g.: charm cross section at fixed target: e.g.: charm cross section at fixed target: [Mangano: hep-ph/9711337]

18. FA - HIM, Seoul - 18 April 2007 18 results depend on the values of: results depend on the values of: m c, µ R (renormalization scale), µ F (factorization scale) m c, µ R (renormalization scale), µ F (factorization scale) the result of an exact calculation would be independent of the choice of the scale parameters µ R, µ F the result of an exact calculation would be independent of the choice of the scale parameters µ R, µ F the residual scale dependence is a measure of the accuracy of the calculation the residual scale dependence is a measure of the accuracy of the calculation e.g.: for b production at Tevatron (µ R =µ F =µ): e.g.: for b production at Tevatron (µ R =µ F =µ): [Mangano: hep-ph/9711337]

19. FA - HIM, Seoul - 18 April 2007 19 it is important to match the PDFs with the order of the calculation. it is important to match the PDFs with the order of the calculation. e.g. one must avoid double counting: e.g. one must avoid double counting: at LO: at LO: at NTLO: at NTLO: “intrinsic flavour” “flavour excitation” Q Q QQ

20. 20 FA - HIM, Seoul - 18 April 2007 Heavy Flavour in p/  -A

21. FA - HIM, Seoul - 18 April 2007 21 Nuclear shadowing PDFs in the nucleus different from PDFs in free proton PDFs in the nucleus different from PDFs in free proton R = ratio of nuclear to nucleon PDFs R = ratio of nuclear to nucleon PDFs from Deep Inelastic Scattering (e - +p; e - +A), Drell-Yan (p+p, p+A -> l + l - +X) from Deep Inelastic Scattering (e - +p; e - +A), Drell-Yan (p+p, p+A -> l + l - +X) e.g.: R for gluons vs gluon momentum fraction x from EKS parametrization [Eskola et al.: EPJ C9 (1999) 61] typical x for cc production (y  0) typical x for cc production (y  0) x  10 -1 @ SPS x  10 -1 @ SPS x  10 -2 @ RHIC x  10 -2 @ RHIC x  a few 10 -4 @ LHC x  a few 10 -4 @ LHC shadowing antishadowing SPS RHIC LHC

22. FA - HIM, Seoul - 18 April 2007 22 Nuclear dependence From pQCD one expects the cross section for production off nuclei to increase like number of nucleon-nucleon collisions From pQCD one expects the cross section for production off nuclei to increase like number of nucleon-nucleon collisions (“binary collision scaling”)  proportional to number of nucleons (for min. bias collisions): modulo shadowing effects, expected to be small modulo shadowing effects, expected to be small Experimentally: not far... e.g. WA82: Experimentally: not far... e.g. WA82: D production in  - +W/Si at SPS (340 GeV beam momentum) D production in  - +W/Si at SPS (340 GeV beam momentum) (relatively) central production (relatively) central production with  =1 “Feynman’s x”

23. FA - HIM, Seoul - 18 April 2007 23Caveats... i)  = 1 does not work down to pp! i)  = 1 does not work down to pp! e.g.: MacDermott & Reucroft compare pA results with earlier hydrogen data from NA27, good agreement using: e.g.: MacDermott & Reucroft [PLB 184 (1987) 108] compare pA results with earlier hydrogen data from NA27, good agreement using: note: similar situation for light flavours! note: similar situation for light flavours! systematic study by Barton et al. [PRD 27 (1983) 2580], for various reactions at 100 GeV FT e.g.: central for production of , K, p from p on nuclear targets: with

24. FA - HIM, Seoul - 18 April 2007 24 ii) lower  at large x F ? ii) lower  at large x F ? early beam dump experiments, sensitive at large x F (max acceptance for x F  0.5) early beam dump experiments, sensitive at large x F (max acceptance for x F  0.5) (in tracking experiments, typically max. acceptance for x F  0.2) e.g. WA78 [Cobbaert et al.: PLB 191 (1987) 456]  for muons escaping dump (  - A at 320 GeV FT ): note:  is known to decrease note:  is known to decrease with x F for light hadrons [Barton et al.: PRD 27 (1983) 2580]

25. 25 FA - HIM, Seoul - 18 April 2007 Heavy Flavour Fragmentation

26. FA - HIM, Seoul - 18 April 2007 26 Fragmentation function c  D, D takes fraction z of c momentum c  D, D takes fraction z of c momentum fragmentation function: D D/c (z) fragmentation function: D D/c (z) depends only on fraction z depends only on fraction z e.g.: e.g.: Peterson Colangelo-Nason Peterson (  = 0.015) Colangelo-Nason (  = 0.9,  =6.4) e.g.: (parameters from fits to charm production at LEP)

27. FA - HIM, Seoul - 18 April 2007 27 How to measure the fragmentation function? How to measure the fragmentation function? we don’t measure the original Q momentum... we don’t measure the original Q momentum... but in e + e - we do know the Q energy (by energy conservation!) but in e + e - we do know the Q energy (by energy conservation!) e.g.: e.g.: fragmentation functions are usually extracted from e + e - measurements and then used for other collisions fragmentation functions are usually extracted from e + e - measurements and then used for other collisions e-e- Q Q e+e+ Z0Z0

28. FA - HIM, Seoul - 18 April 2007 28 e.g.: fits to charm x = 2E/  s distributions in e + e - : e.g.: fits to charm x = 2E/  s distributions in e + e - : [Cacciari & Greco: PRD55 (1997) 7134] very similar parameters at the two energies (as expected) very similar parameters at the two energies (as expected)  s = 10.6 GeV (ARGUS)  s = 91.2 GeV (OPAL) Peterson fragmentation  = 0.015 (OPAL)  = 0.019 (ARGUS)

29. FA - HIM, Seoul - 18 April 2007 29 like for the PDFs, the fragmentation function has to be matched to order of pQCD calculation like for the PDFs, the fragmentation function has to be matched to order of pQCD calculation e.g. at NTLO the Q can radiate: e.g. at NTLO the Q can radiate: so final energy before so final energy before non-perturbative part of fragmentation lower than at LO  harder fragmentation at NTLO at NTLO:   0.015 at NTLO:   0.015 at LO:   0.06 at LO:   0.06 (e.g.: [Cacciari & Greco: PRD55 (1997) 7134] ) Peterson fragmentation  = 0.015 (NTLO)  = 0.06 (LO) Q Q

30. 30 FA - HIM, Seoul - 18 April 2007 Heavy Flavour at Tevatron

31. FA - HIM, Seoul - 18 April 2007 31 Beauty at Tevatron Discrepancy between pQCD and data seems to have disappeared... Discrepancy between pQCD and data seems to have disappeared... from... from... a factor 5.5 (but only 1.6 ...) to... to... [CDF: PRL 68 (1992) 3403] Run 0 Run II [Cacciari et al: JHEP 0407 (2004)] Spectrum of J/  from secondary B decays

32. FA - HIM, Seoul - 18 April 2007 32 From run I on, important improvements in accuracy: From run I on, important improvements in accuracy: experiment (vertex detectors, high statistics) experiment (vertex detectors, high statistics) prediction (post-HERA PDF sets) prediction (post-HERA PDF sets) Levels of stability over time: Levels of stability over time: no large room for new physics any more... no large room for new physics any more...  for more see, e.g.: [Cacciari et al: JHEP 0407 (2004) 033, Cacciari: hep-ph/0407187, Mangano: hep-ph/0411020] DataPredictions from [Cacciari et al: JHEP 0407 (2004) 033]

33. FA - HIM, Seoul - 18 April 2007 33 What about charm? Nice data from CDF run II Nice data from CDF run II [CDF: Phys.Rev.Lett. 91 (2003) 241804] roughly in agreement with full pQCD calculation roughly in agreement with full pQCD calculation (though prediction somewhat low) A curiosity (?): A curiosity (?): good agreement between data and prediction for bare quark [Vogt: talk at SQM 2004]

34. 34 FA - HIM, Seoul - 18 April 2007 Heavy Flavour in AA

35. FA - HIM, Seoul - 18 April 2007 35 Heavy flavour production in AA binary scaling: binary scaling: can be broken by: initial state effects (modified PDFs) initial state effects (modified PDFs) shadowing shadowing k T broadening k T broadening gluon saturation (colour glass) gluon saturation (colour glass) (concentrated at lower p T ) final state effects (modified fragmentation) final state effects (modified fragmentation) parton energy loss parton energy loss violations of independent fragmentation (e.g. quark recombination) violations of independent fragmentation (e.g. quark recombination) (at higher p T )

36. FA - HIM, Seoul - 18 April 2007 36 PHENIX pp Excess wrt FONLL: Excess wrt FONLL: Similar situation also in CDF: Similar situation also in CDF: [A. Adare et al. (PHENIX) Phys.Rev.Lett. 97 (2006) 252002] Ratio: 1.72  0.02 (stat)  0.19 (sys) (0.3 < p T < 9.0 GeV/c) D0D0 [D. Acosta et al. (CDF) PRL 91 (2003) 241804]

37. FA - HIM, Seoul - 18 April 2007 37 STAR v PHENIX pp ~ a factor 2 discrepancy ~ a factor 2 discrepancy hep-ex/0609010 [J. Lajoie (PHENIX) QM06]

38. FA - HIM, Seoul - 18 April 2007 38 STAR dAu, AuAu Internal consistency Internal consistency [M. Calderon (STAR) QM06]

39. FA - HIM, Seoul - 18 April 2007 39 STAR v PHENIX dAu, AuAu Discrepancy pretty “stable” v system, p T Discrepancy pretty “stable” v system, p T looks like something very basic... looks like something very basic... of course then R AA not too different... of course then R AA not too different... [A. Suaide QM06]

40. FA - HIM, Seoul - 18 April 2007 40 STAR v PHENIX: R AA R AA of non-photonic electrons R AA of non-photonic electrons [A. Suaide QM06]  similar picture from STAR and PHENIX

41. FA - HIM, Seoul - 18 April 2007 41 Heavy flavour energy loss? Energy loss for heavy flavours is expected to be reduced: i)Casimir factor light hadrons originate predominantly from gluon jets, heavy flavoured hadrons originate from heavy quark jets light hadrons originate predominantly from gluon jets, heavy flavoured hadrons originate from heavy quark jets C R is 4/3 for quarks, 3 for gluons C R is 4/3 for quarks, 3 for gluons ii)dead-cone effect gluon radiation expected to be suppressed for  < M Q /E Q gluon radiation expected to be suppressed for  < M Q /E Q [Dokshitzer & Karzeev, Phys. Lett. B519 (2001) 199] [Armesto et al., Phys. Rev. D69 (2004) 114003] Casimir coupling factor transport coefficient of the medium average energy loss distance travelled in the medium  R.Baier et al., Nucl. Phys. B483 (1997) 291 (“BDMPS”)

42. FA - HIM, Seoul - 18 April 2007 42 Large suppression at RHIC! yet, region above 3-4 GeV expected to be dominated by beauty... yet, region above 3-4 GeV expected to be dominated by beauty... [Xin Dong@QM05] n.p. electrons ~ as suppressed as expected for c only (no b) n.p. electrons ~ as suppressed as expected for c only (no b) scaled to M. Cacciari et al., hep-ph/0502203 [J.Bielcik @QM05] disentangling c/b is a must! disentangling c/b is a must! e.g. full reconstruction of D vertices e.g. full reconstruction of D vertices

43. 43 FA - HIM, Seoul - 18 April 2007 Heavy Flavour in Alice

44. FA - HIM, Seoul - 18 April 2007 44 LHC Running conditions: Running conditions: + other ions (Sn, Kr, O) & energies (e.g.: pp @ 5.5 TeV) + other ions (Sn, Kr, O) & energies (e.g.: pp @ 5.5 TeV) *L max (ALICE) = 10 31 ** L int (ALICE) ~ 0.5 nb -1 /year Collision system √s NN (TeV) L 0 (cm -2 s -1 ) Run time (s/year)  geom (b) pp14.0 10 34 * 10 7 0.07 PbPb5.5 10 27 10 6 ** 7.7 pPb8.8 10 29 10 6 1.9 ArAr6.3 10 29 10 6 2.7

45. 45 LHC is a Heavy Flavour Machine! cc and bb rates cc and bb rates ALICE PPR (NTLO + shadowing) ALICE PPR (NTLO + shadowing) 115 / 4.6 0.65 / 0.85 6.6 / 0.2 Pb-Pb 5.5 TeV (5% cent) 0.16 / 0.007 1 / 1 11.2 / 0.5 pp 14 TeV shadowingsystem NN x-sect (mb) total multiplicity PbPb pp PbPb pp cc bb PbPb/pp

46. FA - HIM, Seoul - 18 April 2007 46 ALICE Set- up HMPID Muon Arm TRD PHOS PMD ITS TOF TPC Size: 16 x 26 meters Weight: 10,000 tons

47. FA - HIM, Seoul - 18 April 2007 47 |η| < 0.9: B = 0.4 T TRD TPC ITS with: - Si pixel - Si drift - Si strip Tracking

48. FA - HIM, Seoul - 18 April 2007 48 PIXEL CELL z: 425  m r  : 50  m Two layers: r = 4 cm r = 7 cm  9.8 M Full reconstruction of D decays expected d 0 resolution (  ) expected d 0 resolution (  ) ALICE Silicon Pixels ALICE Silicon Pixels

49. FA - HIM, Seoul - 18 April 2007 49 D0  K-+D0  K-+D0  K-+D0  K-+ expected ALICE performance expected ALICE performance S/B ≈ 10 % S/B ≈ 10 % S/  (S+B) ≈ 40 (1 month Pb-Pb running) S/  (S+B) ≈ 40 (1 month Pb-Pb running) statistical. systematic. p T - differential  similar performance in pp (wider primary vertex spread) (wider primary vertex spread)

50. FA - HIM, Seoul - 18 April 2007 50 Beauty to electrons Expected ALICE performance (1 month Pb-Pb) Expected ALICE performance (1 month Pb-Pb) e ± identification from TRD and dE/dx in TPC e ± identification from TRD and dE/dx in TPC impact parameter from ITS impact parameter from ITS S/(S+B) S per 10 7 central Pb-Pb events

51. FA - HIM, Seoul - 18 April 2007 51 Expected performance on D, B R AA m b = 4.8 GeV D 0  K    B  e + X 1 year at nominal luminosity (10 7 central Pb-Pb events, 10 9 pp events) should clarify the heavy flavour quenching story should clarify the heavy flavour quenching story mass dependence colour charge dependence

52. FA - HIM, Seoul - 18 April 2007 52 Heavy Flavour v 2 v 2 = azimuthal anisotropy  elliptic flow v 2 = azimuthal anisotropy  elliptic flow can get charm v 2 from can get charm v 2 from direct charm elliptic flow direct charm elliptic flow non-flowing c recombining with flowing matter non-flowing c recombining with flowing matter azimuthally dependent energy loss azimuthally dependent energy loss...?...?  in general, v 2  0 if charm “strongly coupled” with azimuthally asymmetric medium...

53. FA - HIM, Seoul - 18 April 2007 53 puzzle: at QM`05 different results from PHENIX and STAR... puzzle: at QM`05 different results from PHENIX and STAR... [F.Laue@QM`05] PHENIX: PHENIX: subtraction of conversions by converter method and cocktail subtraction of conversions by converter method and cocktail STAR: STAR: rejection of conversions by inv. mass combinations rejection of conversions by inv. mass combinations @ RIKEN-BNL heavy flavour workshop in december STAR said measurement affected by “too much photonic background” @ RIKEN-BNL heavy flavour workshop in december STAR said measurement affected by “too much photonic background” electron v2 at RHIC

54. FA - HIM, Seoul - 18 April 2007 54 question: question: to what extent can one accommodate small v 2 with large suppression? [S.Butsyk@QM`05] [Xin Dong@QM05]

55. FA - HIM, Seoul - 18 April 2007 55 Charm v 2 at LHC? Full reconstruction of D decays at LHC Full reconstruction of D decays at LHC qualitatively different measurement from non-photonic electrons! qualitatively different measurement from non-photonic electrons! better correlation with original heavy-quark momentum better correlation with original heavy-quark momentum b vs c b vs c First indications from preliminary studies in ALICE: expected error ~ few % (D v 2 ) First indications from preliminary studies in ALICE: expected error ~ few % (D v 2 )

56. FA - HIM, Seoul - 18 April 2007 56 Ds+Ds+Ds+Ds+ D s + as probe of hadronization? D s + as probe of hadronization? from string fragmentation: cs / cd ~ 1/3 from string fragmentation: cs / cd ~ 1/3 after decays: D s + (cs) / D + (cd) ~ 0.6 after decays: D s + (cs) / D + (cd) ~ 0.6 from recombination: cs / cd ~ N(s) / N(d) from recombination: cs / cd ~ N(s) / N(d)  how large at LHC? experimentally accessible? experimentally accessible? D + (c  ~ 310 µm)  K -  +  + with BR ~ 9.2 % D + (c  ~ 310 µm)  K -  +  + with BR ~ 9.2 % in Alice: probably similar performance as for D 0  K -  + in Alice: probably similar performance as for D 0  K -  + D s + (c  ~ 150 µm)  K - K +  + with BR ~ 4.4 % D s + (c  ~ 150 µm)  K - K +  + with BR ~ 4.4 % but mostly resonant decays:  + or K 0 * K + (non resonant only 20 %) but mostly resonant decays:  + or K 0 * K + (non resonant only 20 %)  favours bkgnd rejection (for D +  K -  +  +, non-resonant ~ 96 %)  may be well visible (expecially if D s + /D + is large!) D s v 2 would be particularly interesting! D s v 2 would be particularly interesting!

57. FA - HIM, Seoul - 18 April 2007 57 Heavy flavour jets? 2 GeV 20 GeV 100 GeV 200 GeV Mini-Jets 100/event 1/event 100k/month Well visible event-by-event! e.g. 100 GeV jet + underlying event Well visible event-by-event! e.g. 100 GeV jet + underlying event For high energy jets: Nb ~ Nu,d For high energy jets: Nb ~ Nu,d  heavy flavour rich! b-tagged jets? b-tagged jets?  study quenching of b jets!

58. FA - HIM, Seoul - 18 April 2007 58 Away side cone? Collective behaviour opposite to jet? Collective behaviour opposite to jet? eg: Mach cone eg: Mach cone [Casalderrey-Solana, et al.: hep-ph/0411315] [Stocker: Nucl.Phys. A750 (2005) 121]) What happens with big-fat-heavy quark jets? What happens with big-fat-heavy quark jets? PHENIX Preliminary  *=   *=  John Lajoie @ QM2006

59. FA - HIM, Seoul - 18 April 2007 59 Modified Mach cone? Heavy quarks at moderate p T move with substantially lower speed Heavy quarks at moderate p T move with substantially lower speed e.g.: for beauty, taking: e.g.: for beauty, taking: c S 2 = 0.2 c S 2 = 0.2 m(b) = 4.5 GeV m(b) = 4.5 GeV  b quark is “subsonic” for p < 2.25 GeV  for p ~ 3-4 GeV, shock wave angle ~ 40 O [FA, E Shuryak: J.Phys. G31 (2005) 19] p(b) [GeV] shock wave angle [degrees] Now: observing THAT would be something!

60. FA - HIM, Seoul - 18 April 2007 60Conclusion Heavy flavours kindly provide us with a very promising tool to study the properties of the strongly interacting medium produced in ultra-relativistic nucleus-nucleus collisions Heavy flavours kindly provide us with a very promising tool to study the properties of the strongly interacting medium produced in ultra-relativistic nucleus-nucleus collisions LHC is the place to be  very high rates LHC is the place to be  very high rates p T reach p T reach recombination? recombination? jets? jets? ALICE is well equipped for heavy flavour physics ALICE is well equipped for heavy flavour physics