Heavy Flavour in ALICE

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Heavy Flavour in ALICE

• Federico Antinori
• (INFN Padova Italy)
• for the ALICE Collaboration

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Menu

• Appetizers
• Heavy flavour production at LHC
• c and b as probes of the medium
• Main Courses
• ALICE layout
• D0 ? K-p
• B ? e
• B ? µ
• Desserts
• v2
• D
• Ds
• b jets
• Fortune Cookie

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Appetizers

• Heavy flavour production at LHC
• c and b as probes of the medium

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LHC

• Running conditions
• other ions (Sn, Kr, O) energies (e.g. pp _at_
  5.5 TeV)

Lmax (ALICE) 1031
Lint (ALICE) 0.5 nb-1/year
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Heavy Flavour _at_ LHC

• cc and bb rates
• ALICE PPR (NTLO shadowing)

cc
bb
PbPb/pp
PbPb/pp
PbPb
PbPb
pp
pp
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• large cross-sections
• low-x (a field of its own!)

? accessible x1, x2 regions in the ALICE
experiment
muon arm
central detector
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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

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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
• heavy flavour should provide a fundamental
  cross-check of quenching picture emerging from
  RHIC

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Large suppression at RHIC!

• yet, region above 3-4 GeV expected to be
  dominated by beauty...

• n.p. electrons as suppressed as expected for c
  only (no b)

Xin Dong_at_QM05

• disentangling c/b is a must!
• e.g. full reconstruction of D vertices

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Main courses

• ALICE layout
• D0 ? K-p
• B ? e
• B ? µ, µµ

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ALICE Set-up
Size 16 x 26 meters Weight 10,000 tons
TOF
TRD
HMPID
ITS
PMD
Muon Arm
PHOS
TPC
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Tracking
? lt 0.9 B 0.4 T TRD TPC ITS with - Si
pixel - Si drift - Si strip
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Full reconstruction of D decays

• ALICE Silicon Pixels

• expected d0 resolution (s)

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D0 ? K-p

• expected ALICE performance
• S/B 10
• S/?(SB) 40 (1 month
  Pb-Pb running)

• ? similar performance in pp
• (wider primary vertex spread)

pT - differential
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Beauty to electrons

• Expected ALICE performance (1 month Pb-Pb)
• e identification from TRD and dE/dx in TPC
• impact parameter from ITS

S/(SB)
S per 107 central Pb-Pb events
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Electrons (from b) pt spectrum
Error composition
stat ? syst error
stat error
11 from overall normalization not included
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Expected performance on D, B RAA
mass dependence
colour charge dependence
D0 ? K-p
B ? e X
1 year at nominal luminosity (107 central Pb-Pb
events, 109 pp events)

• should clarify the heavy flavour quenching story

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Beauty to single muons

• expected in the muon arm

? very high statistics and heavy flavour purity
expected
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Beauty to dimuons

• Two main sources

BDSAME
BBDIFF

• Consistency check!

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Desserts

• v2
• D
• Ds
• b jets

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Heavy Flavour v2

• v2 azimuthal anisotropy ? elliptic flow
• can get charm v2 from
• direct charm elliptic flow
• non-flowing c recombining with flowing matter
• azimuthally dependent energy loss
• ...?
• in general, v2 ? 0 if charm strongly coupled
  with azimuthally asymmetric medium...

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electron v2 at RHIC

• puzzle at QM05 different results from PHENIX
  and STAR...

• PHENIX
• subtraction of conversions by converter method
  and cocktail
• STAR
• rejection of conversions by inv. mass
  combinations
• _at_ RIKEN-BNL heavy flavour workshop in december
  STAR said measurement affected by too much
  photonic background

F.Laue_at_QM05
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• question
• to what extent can one accommodate small v2 with
  large suppression?

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Charm v2 at LHC?

• Full reconstruction of D decays at LHC
• qualitatively different measurement from
  non-photonic electrons!
• better correlation with original heavy-quark
  momentum
• b vs c
• First indications from preliminary studies in
  ALICE expected error few
  (D v2)

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D ? K-pp

• Preliminary study performance comparable to that
  for D0 ? K-p

Pb-Pb significance 30 (1 month)
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Ds

• Ds as probe of hadronization?
• from string fragmentation cs / cd 1/3
• after decays Ds (cs) / D (cd) 0.6
• from recombination cs / cd N(s) / N(d)
• ? how large at LHC?
• experimentally accessible?
• D (ct 310 µm) ? K-pp with BR 9.2
• in Alice probably similar performance as for D0
  ? K-p
• Ds (ct 150 µm) ? K-Kp with BR 4.4
• but mostly resonant decays Fp or K0K (non
  resonant only 20 )
• ? favours bkgnd rejection (for D ? K-pp,
  non-resonant 96 )
• may be well visible (expecially if Ds/D is
  large!)
• Ds v2 would be particularly interesting!

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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

• For high energy jets Nb Nu,d
• heavy flavour rich!
• b-tagged jets?
• study quenching of b jets!

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Fortune Cookie
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Away side cone?

• Collective behaviour opposite to jet?
• eg Mach cone

John Lajoie _at_ QM2006

• Casalderrey-Solana, et al. hep-ph/0411315
• Stocker Nucl.Phys. A750 (2005) 121)

• What happens with big-fat-heavy quark jets?

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Modified Mach cone?

• Heavy quarks at moderate pT move with
  substantially lower speed
• e.g. for beauty, taking
• cS2 0.2
• m(b) 4.5 GeV
• b quark is subsonic
• for p lt 2.25 GeV
• for p 3-4 GeV,
• shock wave angle 40O
• FA, E Shuryak J.Phys. G31 (2005) 19

shock wave angle degrees
Now observing THAT would be something!
p(b) GeV
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Digestive
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Startup Plans

• Timeline
• August 2007 close experiment
• September November commissioning
• November December pp commissioning run (vs
  0.9 TeV)
• 2008 first pp run (vs 14 TeV)
• followed by first Pb-Pb run (end 2008?)
• final timing depends on physics landscape by then
• vs 5.5 TeV, L 51025 cm-2s-1
• Startup configuration for 2007
• complete ITS, TPC, HMPID, muon arm, PMD, trigger
  dets (V0, T0, ZDC, Accorde),..
• partially complete PHOS(1/5), TOF(9/18), TRD
  (2-3/18), DAQ (20)

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D0 in pp

• D0 ? K-p

• 1 year run ? 109 events
• 20 shifts, 10 hrs each ? a few 107 events
• reach out to 12 GeV or so

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Example B in pp

• B ? e X
• electron id in TRD and TPC, electron impact
  parameter from ITS

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Conclusion

• 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
• pT reach
• recombination?
• jets?
• ALICE is well equipped for heavy flavour physics

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??

• For much more see
• ALICE Physics Performance Report, Vol. II,
  Journal of Physics G 32 (11), 2137 (2006)