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Heavy-flavour quenching studies with ALICE

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### Heavy-flavour quenching studies with ALICE

1st ALICE Physics Week

Andrea Dainese

Padova – Università e INFN

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

Contents

- Introduction
- Why? (see Carlos’ talk)
- Which observables?

- Possibilities with ALICE (landscape of channels)
- here, focus on D0 Kp and B e+X

- 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

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

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.

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

RD/h enhancement probes color-charge dep. of E loss

RB/h enhancement probes mass dep. of E loss

Color-charge and mass dep. of E loss with Heavy-to-Light ratios at LHCHeavy-to-light ratios:

Compare g h , c D and b B

Armesto, Dainese, Salgado, Wiedemann, PRD71 (2005) 054027

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

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

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

vs FONLL uncertainty band

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. c+b electrons at 200 GeV)
theoretically-understood reference needed

also for observation (see Carlos’ talk)

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

pQCD predictions for heavy quark production at the LHC:

NLO MNR

charm

beauty

beauty

charm

12%

8%

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

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

Calibrating the probe in ALICE

B e + X

D0 Kp

(see C.Bombonati’s talk)

NEW!

pp, s = 14 TeV

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

Expected Sensitivity to RAA

B e + X

D0 Kp

NEW!

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

mb = 4.8 GeV

Low pt (< 6–7 GeV/c)

Nuclear shadowing (here EKS98)

Understanding RAAB e + X

D0 Kp

NEW!

Warning: 5 suppression 2.2 larger statistical errors!

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

The role of the initial state

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

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

mb = 4.8 GeV

Low pt (< 6–7 GeV/c)

Nuclear shadowing (here EKS98)

High pt (> 6–7 GeV/c)

Only parton energy loss?

Understanding RAAB e + X

D0 Kp

beware of in-medium hadronisation …

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

107 min. bias Pb-Pb evts

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 @ 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

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

Heavy-to-light ratios in ALICE

in progress: devise how to use to electrons from B

to build a RB/h, or RB/D …

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

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 W’s as reference
- heavy-quark jet studies (azimuthal correlations, b-tagged jets)

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

EXTRA SLIDES

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

fgPb(x)/fgp(x)

a

b

c

xa

xa+xb

see talk by R. Grosso

xb

Nuclear Shadowing and CharmFor charm at pt 0:

- x1~x2 ~ 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 c&b yield at low pt
- Look at low-pt D in p-Pb!

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

LHC

RHIC

Au-Au 200 GeV

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. Cto appear, hep-ph/0406201.

N.Armesto, A.D., C.A.Salgado and U.A.Wiedemann, in preparation.

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

pp

Study shadowing in p-Pb at 8.8 TeV?R.Grosso, PhD thesis (2004)

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

Theoretical Uncertainties(HERA-LHC Workshop)

Evaluation of theoretical uncertainties

charm

beauty

MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese

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