Andrea Dainese

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Heavy-flavour quenching studies with ALICE
1st ALICE Physics Week

• Andrea Dainese
• Padova Università e INFN

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Contents

• Introduction
• Why? (see Carlos talk)
• Which observables?
• Possibilities with ALICE (landscape of channels)
• here, focus on D0 ? Kp and B ? eX
• Nuclear modification factors
• pp, the importance of the baseline
• expected uncertainties and coverage in pt
• Understanding RAA
• the role of the initial state
• the role of hadronisation

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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.
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Color-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
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How in ALICE (non-exaustive list)

• Charm mesons at central rapidity y (D0 ? Kp, D ?
  Kpp )
• A.D., E.Bruna
• Electrons from beauty at central y
• R.Turrisi, C.Bombonati
• Muons from beauty at forward y
• R.Guernane
• Muons from W at forward y
• Z.Conesa del Valle

RAA and RD/h
RAA (and RB/h?)
RAA
RAA at W/b m crossing in pt
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Role of pp reference for RAA (at RHIC)

• Exclusive measurements at same energy in AA and
  pp (e.g. p0 at 200 GeV)
• experimental reference sufficient for solid
  observation of high-pt quenching
• not sufficient for interpretation in terms of
  parton energy loss
• ? theoretically-understood reference needed
• Inclusive measurement at same energy in AA and pp
  (e.g. cb electrons at 200 GeV)
• ? theoretically-understood reference needed
• also for observation (see Carlos talk)

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Role of pp reference for RAA (at LHC)

• Exclusive measurements at different energy in AA
  and in pp
• ? Need to calibrate the probe translate the
  pp reference from 14 to 5.5 TeV

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Calibrating the probe in ALICE
D0 ? Kp
B ? e X
(see C.Bombonatis talk)
NEW!
pp, ?s 14 TeV
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Expected Sensitivity to RAA
D0 ? Kp
B ? e X
NEW!
15 systematic from efficiency corrections 15
12 theory uncertainty in energy extrapolation 8
-- charm electron subtraction 5
8 normalization error (ltNcollgt) 8
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Understanding RAA
D0 ? Kp
B ? e X
NEW!
Warning ? 5 suppression ? ? 2.2 larger
statistical errors!
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The role of the initial state

• Effect of nuclear modification of the initial
  state PDFs may be tackled by charm measurement in
  pPb

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Understanding RAA
D0 ? Kp
B ? e X
beware of in-medium hadronisation
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The role of hadronisation

• Lowish pt D and B mesons may hadronise inside the
  medium via coalescence ? no clean study of parton
  E loss
• Up to which pt is this relevant?
• ? Study particle type-dependence of RCP

RHIC

• ALICE _at_ LHC
• kaons and hyperons
• (see talks in soft physics sessions)
• D meson RCP sensitivity under study

E loss only
? breakdown of n-quark scaling of v2 can also
help to identify safe pt region
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Heavy-to-light ratios in ALICE
in progress devise how to use to electrons from
B to build a RB/h, or RB/D
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Summary

• Observation of (large) heavy-quarks quenching at
  RHIC has boosted the interest for these studies
  at LHC
• ALICE at LHC in excellent position
• dedicated detectors (ITS)
• large production cross sections
• Promising performance for RAA of D mesons and
  electrons from B mesons
• Other observables need to be studied
• muons from B at forward rapidity
• use of Ws as reference
• heavy-quark jet studies (azimuthal correlations,
  b-tagged jets)

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EXTRA SLIDES
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Nuclear Shadowing and Charm

• For charm at pt ? 0
• x1x2 10-4 at y 0
• min(x1,x2) 10-5 at y ?3

Bjorken

• Pb nucleus 105 partons (mainly gluons)
• they are so close that they fuse
• Shadowing suppression of small-x PDFs
• Reduces cb yield at low pt
• Look at low-pt D in p-Pb!

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Estimates of RAA for D and B

• Ingredients BDMPS quenching weights for heavy
  quarks Glauber-based medium geometry LHC
  medium density extrapolated on the basis of
  hadron suppression at RHIC

RHIC analysis A.D., C.Loizides and G.Paic, Eur.
Phys. J. C to appear, hep-ph/0406201. N.Armesto,
A.D., C.A.Salgado and U.A.Wiedemann, in
preparation.
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Study shadowing in p-Pb at 8.8 TeV?
R.Grosso, PhD thesis (2004)
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Theoretical Uncertainties(HERA-LHC Workshop)
Evaluation of theoretical uncertainties
beauty
charm
MNR code Mangano, Nason, Ridolfi, NPB373 (1992)
295.