Heavy Flavour in ALICE

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Heavy Flavour in ALICE

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

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Contents

• The LHC, Heavy Flavours and ALICE
• or ALICE in Wonderland
• Benchmark channels
• D0 ? K-p
• B ? e X
• B ? µ X
• Additional measurements under investigation
• D ? K-p p
• B ? J/y X
• v2
• Ds
• b tagged jets
• Coming up pp
• Conclusion

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The LHC, Heavy Flavours and ALICE
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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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• study medium with probes of known colour charge
  and mass
• e.g. energy loss by gluon radiation expected to
  be
• parton-specific stronger for gluons than quarks
  (colour charge ratio 9/4)
• flavour-specific stronger for lighter than for
  heavier quarks (dead-cone effect)
• study effect of medium on fragmentation (no extra
  production of c, b at hadronization)
• independent string fragmentation vs recombination
• e.g. Ds/D
• measurement important for quarkonium physics
• open QQ production natural normalization for
  quarkonium studies
• B meson decays non negligible source of
  non-prompt J/y at LHC

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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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By the way the factor 9/4?

• energy loss should be proportional to
  CR 4/3 for q, 3 for g
• at RHIC, at 6-8 GeV pT x 10-1
• large quark contribution also for light flavours?
• at LHC, at same pT x a few 10-4
• quark contribution negligible

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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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ALICE Status

• Timeline
• Installation commissioning ongoing
• Global commissioning in December February
  (cosmics)
• April 2008 on cosmics, then pp run
  (commissioning ? physics)
• followed by first Pb-Pb run (vs 5.5 TeV, L
  51025 cm-2s-1)
• Startup configuration
• complete ITS, TPC, TOF, HMPID, muon arm, PMD,
  trigger dets (V0, T0, ZDC, Acorde)
• partially complete PHOS (3/5), TRD (5/18),
  DAQ/HLT (20-30)

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Tracking
? pixel - Si drift - Si strip
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Inner Tracking System (ITS)
longitudinal coverage h (multiplicity)
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ITS Installation
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Silicon Pixel Detector (SPD)
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Expected resolution
on track impact parameter

• track impact parameter (d0)

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Benchmark channels
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D0 ? K-p

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

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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Additional measurements under investigation
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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 expect 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!)
• Under study!

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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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Non photonic el. v2 _at_ RHIC

• to what extent can one accommodate small v2 with
  large suppression?

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Reconstructed D 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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B ? J/y X

• More exclusive than B ? e/µ X
• better handle on B momentum distribution
• Preliminary pp study pseudoproper decay time
• (à la CDF)

CDF (data)
pT0
ALICE (prelim. simulation)
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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!
• Preliminary look impact parameter tagging looks
  promising (full simulation needed)

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Coming up pp
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Example 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 ? e X in pp

• 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
• At LHC
• ? very high rates
• ? very extended pT range
• ? well developed jets
• ALICE is well equipped for heavy flavour physics