ALICE potential for heavy-flavour physics

SQM 2007 - Levoca, 28.06.07 Andrea Dainese 1

ALICE potential for ALICE potential for heavy-flavour physicsheavy-flavour physics

SQM 2007SQM 2007LevoLevočča, Slovakia, June 24-29, 2007a, Slovakia, June 24-29, 2007

Andrea DaineseINFN – Legnaro

for the ALICE Collaboration


Contents

Charm and beauty at the LHC

Physics motivation for open flavour and quarkonia measurements

Heavy-flavour program in ALICE

Measurements in preparation

Examples of expected performance (charm & quarkonia)

more on beauty J.Faivre’s talk


LHC: hard cross sectionslots of heavy quarks!

NLO predictions (ALICE baseline for charm & beauty)

* M.Mangano

system, s pp, 14 TeV Pb-Pb (0-5%), 5.5 TeV

11.2 / 0.5 4.3 / 0.2

0.16 / 0.007 115 / 4.6

[mb] QQNNQQ

totN

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

beautycharm

factor ~2uncertainty


Probe unexplored small-x region with HQs at low pt and/or forward y

Charm measurements at low-pt or forward y

Window on high-density PDFs phenomenology:

gluon saturation / recombination effects / CGC

The charm of small-x gluons

Cartoon

char

mbea

uty

D mesons pt0, y=0 J/ pt0, y4

x~10-4x~10-6

s=14 TeV

s=14 TeV


Heavy quarks as medium probes:Energy Loss

Parton Energy Loss by medium-induced gluon radiation collisions with medium gluons

q: colour triplet

QCD medium

u,d,s: m~0, CR=4/3(difficult to tag at LHC)

g: m=0, CR=3> E loss, dominant at LHC

c: m~1.5 GeV, CR=4/3small m, tagged by D’sb: m~5 GeV, CR=4/3large mass, < E loss

Parton Energy Loss by medium-induced gluon radiation collisions with medium gluons

pred:

),,;( LmCE RQGPbqcg EEE

BAA

DAAAA RRR

Q: colour triplet

g: colour octet

Dokshitzer and Kharzeev, PLB 519 (2001) 199. Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003.

Djordjevic, Gyulassy, Wicks, nucl-th/0512076


Energy loss, from RHIC to LHC (I)

Armesto, Cacciari, Dainese, Salgado, Wiedemann, “Last Call for LHC Predictions” workshop

Radiative energy loss (BDMPS): charm ~ m=0 quark probe colour charge dependence; beauty probe mass dependence

Au-Au 200 GeV Pb-Pb 5.5 TeV

)()()(/ tDAAt

BAAtDB pRpRpR

massive

heavy-to-light ratio


Energy loss, from RHIC to LHC (II)

Wicks, Gyulassy, “Last Call for LHC Predictions” workshop

Heavy quarks (esp. beauty) may help to disentangle relative importance of radiative and collisions losses

see also talk by W.Horowitz


Energy loss, from RHIC to LHC (III)

I.Vitev, A.Adil, “Last Call for LHC Predictions” workshop

Conceptually different approach: Fragmentation & dissociation of heavy-flv hadrons inside QGP

D

B

D+B


Heavy quarks as medium probes:Azimuthal asymmetry (v2)

v2 of D and B mesons in non-central collisions tests:

at low/moderate pt: recombination scenario, flow of c/b quarks (?), hence degree of thermalization of medium

van Hees, Rapp, Greco, “Last Call for LHC Predictions” workshop

Armesto, Cacciari, Dainese, Salgado, Wiedemann, “Last Call for LHC Predictions” workshop

at higher pt: path-length dependence of E loss in almond-shaped medium

RHIC LHC


Quarkonia at LHC: (cc) & (bb) J/ suppression & regeneration?

c, ’ suppression (J/ TD ~ 1.5-2 Tc)?

SPSRHICLHC

30

enhanced suppression

enhanced regeneration

TLHC >> J/ TD

melts only at LHC

’ TD ~ J/ TD

Small regeneration ’ can unravel J/ suppression VS regeneration


The ALICE DetectorThe ALICE Detector

||| < 0.9, B = 0.5 T| < 0.9, B = 0.5 TTPC + silicon trackerTPC + silicon tracker,,ee, , , K, p identification, K, p identification

-4 < -4 < < -2.5 < -2.5muonsmuons

ALICE Collaboration: >1000 people, 30 countries, ~ 90 Institutes

Size: 16 x 26 meters

Weight: 10,000 tons


Getting Ready for Beam!

Ready to move

TPC (largest ever) installed, ITS moving in

MUON arm: largest dipole ever


Open charm and beautyOpen charm and beauty

TPC (tracking)

TOF (K/ id)

ITS (vertexing)

K

D0 K D+ K Ds KK D* D0 D0 K c Kp

understudy


understudy

B e+X B 5 pr. B J/ee

understudy

ITS (vertexing)TPC (tracking e/ id)TRD (e/ id)

e

TPC (tracking)ITS (vertexing)MUON (tracking,id)

B +X


understudy

B e+X B 5 pr. B J/ee

understudy


PrimaryVertex B

e

Xd0

rec. track

Vertexing: track d0 resolution

< 60 m (r)for pT > 1 GeV/c

Resolution mainly provided by the 2 layers of silicon pixels

PIXEL CELL

z: 425 m

r: 50 m

Two layers:r = 4 cmr = 7 cm

9.8 M


pair of opposite-charge tracks with large impact parameters

good pointing of reconstructed D momentum to the primary vertexD0

Charm reconstruction: D0 K-+ & D+ K-++

Two vertexing algos with full error-matrix treatment

Large combinatorial background (dNch/dy=6000 in Pb-Pb simul.)

Main selection: displaced-vertex selection

Invariant mass analysis

large distance (dPS) between primary and secondary vertex

good pointing of reconstructed D momentum to the primary vertexD+

1 year at nominal luminosity(109 pp events, 107 central Pb-Pb events)

10

20

30

40

50

D0 D+


Beauty in the barrel: displaced e’s, displaced J/ee

Excellent electron identification capabilities (TPC and TRD)

Displaced electrons/di-electrons from B decays tagged by an impact parameter cut (ITS)

see talk by J.Faivre

J/ e+e-

)/()/( /

Jp

MJL

T

Jxy

primarysecondary

J/ pseudoproper decay time (pt>5GeV)


Charm and Beauty E Loss : RAA

mb = 4.8 GeV

D0 K

B e + X

1 year at nominal luminosity(107 central Pb-Pb events, 109 pp events)

D+ K

mC = 1.2 GeV

mC = 0

B eE loss calc.:Armesto, Dainese, Salgado, Wiedemann


Heavy-to-light ratios

1 year at nominal luminosity(107 central Pb-Pb events, 109 pp events)

)()()(/ thAAt

DAAthD pRpRpR probes colour-charge dep.

of QCD energy loss

)()()( D from eB from e/ tAAtAAtDB pRpRpR

probes mass dep.of QCD energy loss

E loss calc.:Armesto, Dainese, Salgado, Wiedemann


Charm v2: D+ example

First estimate of statistical errors on D+ v2:

best sensitivity at intermediate pt: 3 – 7 GeV/c charm recombination

Under study: performance with D0 + D+

2107 min.bias evts 2107 6<b<9 fm evts

v2 calc. from Ko et al.


Beauty via (forward) muons

inner bars: stat. errorsouter bars: syst. errors

Muons “identified” in the spectrometer (-4 << -2.5)

Pb-Pb 0-5%(1 month)

W (medium-blind reference) dominates for pt > 30 GeV/c!!

ALICE muon spectrometer acc.:-4 < < -2.5, pt > 1 GeV, p > 4 GeV

single muons in the spectrometer: b dominates for pt > 2-3 GeV/c

thin: no mass effectthick: mass effect

RCP

b quarkE loss


ITS (vertexing)TPC (tracking)TRD (e/ id)

MUON (tracking,id)

e e

QuarkoniaMeasured both in the di-electron (midrapidity, TRD) and di-muon (forward rapidity, MUON) channel


Particle Charmonia +- Charmonia e+e- Bottonia +- Bottonia e+e-

Bkg-subtracted

mass plot

acc. -4 < < -2.5 || < 0.9 -4 < < -2.5 || < 0.9

M res. 65 MeV 35 MeV 90 MeV 90 MeV

J/ 150, ’ 7 J/ 245 30, ’ 12,

’’ 8 21, ’ 8

perf. , ?’ , ??’ , ’, ?’’ , ?’, no ’’

pt J/ 0-20 GeV J/ 0-10 GeV 0-8 GeV --

Quarkonia PerformanceBkg input: dNch/dy=4000 in central Pb-Pb. for 1 month

BS

S

BSS /


Medium effect on Quarkonia:Quarkonia/BB , Quarkonia RAA

Normalization of quarkonia yields: BB yield (from intermediate-mass di-leptons), but b E loss?

Possible alternative: RAA (à la PHENIX),

but different c.m.s. energy,

need p-Pb for initial-state effects

Plots for channel


SummaryLHC: heavy quarks and quarkonia factory

Heavy quarks as probes of QCD in extreme conditions

low pt: probe small-x structure of p and nucleus

intermediate pt: probe medium thermalisation (reco/flow)

high pt: probe medium density via energy loss

Charmonia & bottomonia as probes of QCD phase transition

ALICE in excellent position:

dedicated detectors (ITS, TRD, MUON)

promising performance for all key measurementsThanks to:

F.Antinori, C.Blume, C.Bombonati, E.Bruna, G.E.Bruno, Z.Conesa, P.Crochet, H.Ding, J.Faivre, R.Guernane, M.Lunardon, G.Martinez,

M.Masera, F.Prino, R.Turrisiand ALICE “HF & Quarkonia” working group


EXTRA SLIDES


LHC running conditions

Ldt = 5.1026 cm-2 s-1 x 106 s

5.1032 cm-2 PbPb run, 5.5 TeV

NPbPb collisions = 2 .109 collisions

Ldt dt = 3.1030 cm-2 s-1 x 107 s

5.1037 cm-2 for pp run, 14 TeV

Npp collisions = 2 .1012 collisions

Muon triggers: ~ 100% efficiency, ~ 1kHz Electron triggers: Bandwidth limitation NPbPb central = 2 .108 collisions

Muon triggers: ~ 100% efficiency, < 1kHz

Pb-PB nominal run pp nominal run

Electron triggers: ~ 50% efficiency of TRD L1 20 physics events per event

Hadron triggers: NPbPb central = 2 .107 collisions

Hadron triggers: Npp minb = 2 .109 collisions


pp: perspectives for the 1st month

Detector configuration:ITS + TPC + TOF

When? Latest statement from the machine (June 7): “Machine Closure: 31.8.07 Set up of machine, injection, followed by up to 10 weeks of pp collisions: Sept. to Dec. 2007”

Expected statistical errors for a low-stats sample:Scaling of statistical errors according to Nevts

No dedicated cuts study yet

D0 K

Detector configuration:ITS + TPC + TRD

B e + X

~1 month at end 2007

1 year at nominal luminosity


Quarkonia: mass spectraMeasured both in the di-electron (midrapidity, TRD) and di-muon (forward rapidity, MUON) channel

J/ family family

Mμμ (GeV/c)Mμμ (GeV/c)

di-electron ||<0.9

di-muon -4<<-2.5

1 month at nominal luminosity(107 central Pb-Pb events)


Suppression Scenarii

• Suppression-1 Tc =270 MeV D/Tc=1.7 for J/ D/Tc= 4.0 for .

• Suppression-2 Tc=190 MeV D/Tc=1.21 for J/ D/Tc= 2.9 for .PRC72 034906(2005)

Hep-ph/0507084(2005)

Good sensitivity J/, (1S) & (2S)

Ph. CROCHET, F, GUERIN, R. GUERNANE, S. GRIGORYAN et al.

Documents

ALICE potential for heavy-flavour physics