Heavy flavour quenching studies with alice
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1 st ALICE Physics Week. Heavy-flavour quenching studies with ALICE. Andrea Dainese Padova – Universit à e INFN. Contents. Introduction Why? (see Carlos’ talk) Which observables? Possibilities with ALICE (landscape of channels) here, focus on D 0  K p and B  e +X

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Heavy-flavour quenching studies with ALICE

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Heavy flavour quenching studies with alice

1st ALICE Physics Week

Heavy-flavour quenching studies with ALICE

Andrea Dainese

Padova – Università e INFN

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese


Contents

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 r aa at lhc

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


Color charge and mass dep of e loss with heavy to light ratios at lhc

mass effect

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 LHC

Heavy-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

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


Role of pp reference for r aa at rhic

PHENIX preliminary data (QM)

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


Role of pp reference for r aa at lhc

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

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 r aa

Expected Sensitivity to RAA

B  e + X

D0 Kp

NEW!

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese


Understanding r aa

mb = 4.8 GeV

Low pt (< 6–7 GeV/c)

Nuclear shadowing (here EKS98) 

Understanding RAA

B  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

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


Understanding r aa1

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 RAA

B  e + X

D0 Kp

beware of in-medium hadronisation …

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese


The role of hadronisation

Statistical errors for

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

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

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

EXTRA SLIDES

ALICE Physics Week - Erice, 06.12.2005 Andrea Dainese


Nuclear shadowing and charm

fgPb(x)/fgp(x)

a

b

c

xa

xa+xb

 see talk by R. Grosso

xb

Nuclear Shadowing and Charm

For 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


Estimates of r aa for d and b

LHC

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


Study shadowing in p pb at 8 8 tev

p-Pb

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

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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