Charm and beauty with Charm and beauty with ALICE at LHCALICE at LHC

Rosario TurrisiRosario TurrisiUniversity and INFN, Padova, ItalyUniversity and INFN, Padova, Italy

for the ALICE Collaborationfor the ALICE Collaboration

2

ContentsContents

• Heavy flavors and heavy ions• Key performances of ALICE

• Charm cross section and pt sensitivity

• Beauty cross section• Conclusions and Perspectives

3

Heavy flavors and heavy-ionsHeavy flavors and heavy-ions

Why measure heavy flavors at LHC ?– Interest in its own right: discovery potential!

More specific to our issue (hot and dense matter):– quarkonium suppression: deconfinement signature– probes of the medium:

• early formation (initial parton-parton), most energetic phase• thermal (late) production ?• energy loss (medium dependent?)

– B J/ important background for direct J/ – open heavy flavors as natural normalization for QQ studies

pp reactions, pQCD, nuclear effects

(geometry, shadowing)medium propertiesINPUT OUTPUT

PbPb @ =5.5 TeVNNs

not covered here

K

e c D Kb B eX

openflavors

channels

4

Quark energy loss: basicsQuark energy loss: basics

• Common explanation:

parton energy loss due to gluon radiation

– Average energy loss (BDMPS model):

CR Casimir factor = 3 for gluons 4/3 for quarksq = medium transport coefficient gluon density and momenta

2 ˆ LqCE Rs

path length L

c

g

R.Baier, Yu.L.Dokshitzer, A.H.Mueller, S.Peigne' and D.Schiff, Nucl. Phys. B483 (1997) 291.C.A.Salgado and U.A.Wiedemann, Phys. Rev. D68 (2003) 014008 [arXiv:hep-ph/0302184].

tpp

tAA

collAA dpdN

dpdN

NR

/

/1• Study to get the medium effect

RAA measured at RHIC with pions: clear high-pt suppression

RAA =1 if AA is superposition of independent pp collisions

Quark Matter Conference ’04

A.Dainese, C.Loizides and G.Paic, hep-ph/0406201

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Energy loss with heavy flavors ?Energy loss with heavy flavors ?

• Effect present in light mesons, what about other particles?– D,B meson originate from c,b quarks Cr = 4/3, whereas light flavors originate mainly from gluons (C=3)– Dead cone effect*: due to destructive interference, gluons radiation is

suppressed at angles < mQ/EQ

q = 100 GeV2/fm at LHC1

tpp

tAA

collAA dpdN

dpdN

NR

/

/1

*Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/0106202].

1. K.J.Eskola, K.Kajantie, P.V.Ruuskanen and K.Tuominen, Nucl. Phys. B570 (2000) 379 [hep-ph/9909456].

charm

beauty

• Comparison among -D-B in order!

extrapolation from q=15 GeV2/fm at RHIC… a worst case (q=100 GeV2/fm)!

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Cross sectionsCross sections

• NLO pQCD (Mangano-Nason-Ridolfi), average of MRST e CTEQ5M PDF’s, EKS98 in Pb-Pb for shadowing

(shadowing = modification of PDF’s, reduction of cross section)

Taking into account F,R

a factor 4 arises between min. and max. cross section…

In acceptance!D0/ D0 B(s)+ b

pp 0.19 0.0143

PbPb 140 9~0.5 D0 K

~0.2 B eX

Mesons multiplicities central collisions

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Tracking performanceTracking performance

impact parameter resolution:

σ= @ pt=1.3 GeV< 50 μm

< 150 μm z

EFFICIENCYpionskaons

pt resolution:

σ= 1(2)% @ 1(10) GeV 9% @ 100 GeV

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test beam: id. as e = 1 %

PID: e,PID: e,, K, p, K, pPbPb events, dN/dy=6000

TRDTRD

electrons

TPCTPC

hadrons

TOFTOF

Combined π/e ~ 10-4 @ pt~1-2 GeV

p (GeV/c)

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Selection cutsSelection cuts

• D0 K – decay topology– impact parameter of tracks (in bending plane, d0~100 μm)

– momenta– identification

~ 0.5 DD00 with |y|<1 with |y|<1but also 12000 but also 12000 charged charged /K/Kin PbPb collisionsin PbPb collisions

cos(pointing angle) vs. impact parameters product

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Performance: DPerformance: D00KK

• K, MINV integrated over pt

• 107 PbPb events (one-month run)• dN/dy(y=0) = 6000 (charged)

S/Binitial(M3)

S/evtfinal

(M1)

S/Bfinal

(M1)

SignificanceS/S+B(M1)

5 10-6 1.3 10-

3 11 %37

(for 107 evts)

measurement of pt distribution

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Charm energy loss in ALICECharm energy loss in ALICE

Current estimation of q = 100 GeV2/fm

mc=0mc=1.2 GeV/c2

N.Armesto, A.Dainese, C.A.Salgado and U.A.Wiedemann,

in preparation

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• Task: tag ~ 0.8 e /event from b decays among ~ 103 electrons from other sources• Main backgrounds:

– pions misidentified as electrons– Dalitz decays– charm semi-electronic decays– photon conversions in the detector materials– strange decays

• Strategy:– high impact parameter: c ~ 500 μm for beauty – high momenta: beauty harder than lighter flavors – electron/pion separation critical

bb e+X: strategy e+X: strategy

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pptt and d and d00 spectra spectra

beauty electronscharm electronscharged pions

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bb e+X: purity and statistics e+X: purity and statistics

background cure

charm electrons pt thr.

light mesons electrons d0 thr.

charged pions identification

pT> 1 GeV

pT> 2 GeV

pT> 3 GeV

pT>2 GeV, 180 d0 600 m

90% purity

50,000 B's (including TRD efficiency)

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Conclusions & perspectivesConclusions & perspectives• ALICE has a good potential to measure heavy flavors in different channels• Charm:

– production cross section

– pt distribution

– study of energy loss

• Beauty:– Production cross section

• Coming up– reconstruction of b decay topologies

• b’s pt distribution, energy loss study

– additional D, D* channels– semi-electronic charm (beauty background!)– …

11% S/B, significance=37

pT> 1 GeVpT> 2 GeVpT> 3 GeV

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ALICE ALICE detectorsdetectors

Solenoid magnet B<0.5 T

TPC88 m3 , 510 cm length, 250 cm radius Ar (90%) + CO2 (10%)88 μs drift timemain tracking device, dE/dx

2 * 1.8 units of pseudo-rapidity

ITS- 6 Layers, 3 technologies Material budget < 1% of X0 per layer! Silicon Pixels vertices resolution in xy (0.2 m2, 9.8 Mchannels)Silicon Drift resolution in z (1.3 m2, 133 kchannels) Double-sided Strip connection w/TPC (4.9 m2, 2.6 Mchannels)

PIXEL CELL

z: 425 m

r: 50 m

Two layers:r = 4 – 7 cm

9.8 Mch

TRD - 6 layers for:• electron/pion separation at pt>1 GeV

• factor 100 rejection at 2 GeV• tracking complement, mass resolution 100 MeV/c2 @ • high pt trigger (onia studies)

TOFTOF - Multigap Resistive Plate Chambers - Multigap Resistive Plate Chambers < 100 ps < 100 ps pions, kaons, protons separation (see later)electrons/pions at low pt

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60 < < 62

Total charged multiplicityTotal charged multiplicity

TPC + ITSprojection of the full range

(front view)

dNCH/dy (y=0)

Current baseline: 6000

Tested up to: 8000

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Quarkonia detectionQuarkonia detection

• see Andres Sandoval’s talk (I hope…)

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Signal & background ptSignal & background pt

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CentralityCentrality

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LHC run parametersLHC run parameters

System

pp

PbPb

√sNN

(TeV)

L0

(cm-2s-1)dN/dy

(y=0)

TRUN

(s/year)

geom

(b)

14.0 1034* 6 107 0.07

5.5 1027 2-8103 106 * * 7.7

Fall 2007

2008 *Lmax(ALICE) = 1031 ** Lint(ALICE) ~ 0.7 nb-1/year

Pile-up in TPC +and ion-density

limit

tuning orbeam offset

• and, later, more systems: pA, light ions (Sn, Kr, Ar,O) & other energies (pp @ 5.5 TeV).

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x regimex regime

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pQCD pQCD extrapolationsextrapolations

• NLO pQCD (Mangano-Nason-Ridolfi), average of MRST e CTEQ5M PDFs (EKS98 in Pb-Pb for shadowing)

Taking into account F,R

a factor 4 arises between min and max x-section…inclusive cross section alreadya valuable information!

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Hadron multiplicitiesHadron multiplicities

pp

PbPb

~8 B or b ~0.85 B eX

~140 D0/D0 ~5 D0 K

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AcceptanceAcceptance

-6

-4

-3

-2

-1

0

1

2

3

4

90o 180o 270o 360o

Rap

idit

y

Azimuth

FMD -5.4 < < -1.6

PMD -2.3 < < -3.5

FMD 1.6 < < 3

Muon arm 2.4 < < 4

ITS+TPC+TRD+TOF: -0.9 < < 0.9

ITS multiplicity -2 < < 2

HMPID -.45 < < 0.45

PHOS -.12 < < 0.12

SPD multiplicity -2<<2

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b->e+X: contaminationb->e+X: contamination

pt bin [GeV/c]

d0 threshold [m] % S ( bc/b ) % Bcharm % Bother elec. Ns [x104]

1.0 – 1.6 200 – 300 40 – 60 (30%) 30 – 20 30 – 20 9 – 5

1.6 – 2.2 150 – 300 80 – 90 (15%) 20 – 10 – 6 – 2

2.2 – 3.0 150 – 300 > 90 (10%) < 10 – 4 – 2

3.0 – 5.0 100 – 300 > 95 (10%) < 5 – 4 – 1

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Particle identificationParticle identification

Various techniques…

… in a wide momentum range

2 ||<0.9

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Charm detection performanceCharm detection performance

S/Binitial(M3)

S/evtfinal

(M1)

S/Bfinal

(M1)

SignificanceS/S+B(M1)

Pb-Pb 5 10-6 1.3 10-3 11 % 37

(for 107 evts,~1 month)

pp 2 10-3 1.9 10-5 11 % 44

(for 109 evts,~1 year)

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Expected multiplicity/running Expected multiplicity/running conditionsconditions

• ALICE optimized for dN/dy(y=0) =4000-6000, tested extensively up to 8000• Extrapolating from RHIC…

hep-ph0104010

5

√s (GeV)10 102 103 102 103 104

1.0

5.0

10.0

15.0

Nch

/(0

.5N

part)

dN

ch/d|

<1

2

5

103

dNch/d ~ 1300dNch/d ~ 2500

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DD00 K K--++:: dd22(D(D00)/dp)/dpttdy and ddy and d(D(D00)/dy)/dy

d(D0)/dy for|y| < 1 and pt > 1 GeV/c (65% of (pt > 0)) statistical error = 7 % systematic error = 19 % from b = 9 % MC correction = 10% B.R. = 2.4 % from AA to NN = 13 %

d(D0)/dy for|y| < 1 and pt > 0

statistical error = 3 % systematic error = 14 % from b = 8 % MC correction = 10% B.R. = 2.4 % inel = 5 %

inner bars: statisticalouter bars: systematic

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Signal history, errors for Signal history, errors for PbPbPbPb

Selection effectiveness…SignalTotal D0 / event 141decaying in K 5.4with K and in acc. 0.5after track rec. 0.14after (,) rejection 0.13after selection cuts 0.0013

Background

reduced by a factor ~10-7

10-2

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Energy loss vs. dead coneEnergy loss vs. dead cone

D/h ratio: R

D/h = R

AAD / R

AAh

q = 4 GeV2/fm at LHC requiringsame hadron suppression as at RHIC

Quantitative difference heavy/light mesons measurement?

RD/h

~ 2

in hot QGP

sensitive tomedium density

E gluons/quarks energy loss ~ 2

E gluons/quarksfragmentation ~ 1/2

dead cone makes the difference!

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General motivationGeneral motivation

• A Large Ion Collider Experiment is the LHC experiment dedicated to the study of the Quark Gluon Plasma…

QGP a (locally) thermally equilibrated state of matter in which color degrees of freedom become manifest over nuclear, rather than merely nucleonic, volumes.“Partons are deconfined”

strong interaction

LHC

PbPb @ = 5.5 TeVNNs

hadronic matter

QGP

high energy &

large volume

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Performance studiesPerformance studies

• Detector description with the state-of-the-(ALICE)-art code AliRoot

• Charm/beauty signal tuned to NLO pQCD pt spectrum (custom tuning of PYTHIA)• Background from HIJING, 6000 charged particles per unit

rapidity at midrapidity

Priorities:• the exclusive decay of the D0 K (golden channel):

– test bench for secondary vertex detection, pid– very high background

• inclusive b eX decay– secondary vertices – electron identification– “easy” measurement of cross section

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QGP evidences and probesQGP evidences and probes

At LHC (Pb-Pb @ 5.5 ATeV):• more strictly μB=0• higher energy density

• SPS experiments got some evidence that matter may behave in odd ways (not just as “typical” hadrons)

• RHIC exps show confirmation of the new behaviour,mostly with light mesons and hadrons

• Possible improvements: – experimental smoking gun of QGP? (see f.e. T. Hallman talk at ICHEP

2004, Beijing, China)– study of QGP properties?

DEEP DECONFINEMENT?

larger volume

longer lifetime

• Hard cross section dominant• Could heavy flavors represent a good tool at LHC?