Heavy Quarks at the LHC

High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese 1

Heavy Quarks Heavy Quarks at the LHCat the LHC

Heavy Quarks Heavy Quarks at the LHCat the LHC

Andrea DaineseAndrea Dainese

INFN LegnaroINFN Legnaro(ALICE Collaboration)(ALICE Collaboration)


LayoutLayoutHeavy-flavour production in hadronic collisions

pp baseline: pQCD calculations

nuclear effects, in initial and final state

What have we learnt at Tevatron and RHIC?

What will be new at the LHC?

What do we expect?

What should we measure?

Experimental Perspectives at the LHC


Heavy-flavour production: ppHeavy-flavour production: ppproton-proton collisions: factorised pQCD approach

)pp(zDp

xPDFxPDF cDDccT

c

/d

ˆd)()( 21

)~Q~( 2221 ccMsxx

s /2

c

c D

D

x1

x2

Q2

s /2),(d

dRFD

T

D

p

PDF:• Q2 evolution calculated in pQCD• initial condition from data (HERA)

FF: • non-perturbative • phenomenolgy + fit to data (e+e-)

calculable as perturbative series of strong coupling s(R)

22, Q~RF


pp QQ+X: pQCD calculations vs datapp QQ+X: pQCD calculations vs data

Calculation of partonic cross section classic: Fixed Order (NLO) Massive (e.g. MNR code)

state-of-the-art: Fixed Order Next-to-Leading Log (FONLL)

Tp

more accurate at high pT

FONLL: Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033

B production at Tevatron (1.96 TeV)is well described by FONLL

CDF, PRL91 (2003) 241804FONLL: Cacciari, Nason

Charm production slightly underpredictedat Tevatron (1.96 TeV)

Cacciari, Nason, Vogt, PRL95 (2005) 122001

& at RHIC (200 GeV)Q e+X

latest update in the following


Heavy-flavour production: AAHeavy-flavour production: AA

A

A

Binary scaling for hard yields: collDT

Dpp

DT

DAA NpNpN d/dd/d

Binary scaling is “broken” by:

c

c D

D

x

fgPb / fg

p

LHC RHIC SPSRAA <1 ~1 >1

Q2 = 5 GeV2

pT

RA

B

1

~2-4 GeV/c

kL kT

Cronin enhancement

• initial-state effects: PDF shadowing kT broadening (‘Cronin’)

medium formed in the collision

A

A c

cD

Du

• final-state effects energy loss? [next slide]

in-medium hadronization (recombination?)

recombination: pH = pq

fragmentation: pH = z pq

baryon/meson enhancement

Calculating Parton Energy LossCalculating Parton Energy Loss


cc

ccRsC

I

for )/(

for /

d

d2

Baier, Dokshitzer, Mueller, Peigné, Schiff, NPB 483 (1997) 291.Zakharov, JTEPL 63 (1996) 952.Salgado, Wiedemann, PRD 68(2003) 014008.

BDMPS-Z formalismpath length L

kT

Radiated-gluon energy distrib.:

2

ˆTk

q transport coefficient

2/ˆ 2Lqc LR c

sets the scale of the radiated energyrelated to constraint kT < , controls shape at << c

Casimir coupling factor: 4/3 for q, 3 for gRC

(BDMPS case)


Models vs RHIC “light” dataModels vs RHIC “light” dataModel: pQCD + E loss probability + detailed collision geometry

Density ( ) “tuned” to match RAA in central Au-Au at 200 GeV

/fmGeV 144ˆ 2q

q

matches pT-indepence of suppression at high pT

Dainese, Loizides, Paic, EPJC 38 (2005) 461.

(Quark Matter 05)

Same theoretical calculation (SW quenching weights) and similar results in Eskola, Honkanen, Salgado, Wiedemann, NPA747 (2005) 511

Tpp

TAA

collTAA dpdN

dpdN

NpR

/

/1)(

PRL101 (2008) 232301

Lower E loss for heavy quarks ?Lower E loss for heavy quarks ?


In vacuum, gluon radiation suppressed at < mQ/EQ

“dead cone” effect

Dead cone implies lower energy loss (Dokshitzer-Kharzeev, 2001):• energy distribution d/d of radiated gluons suppressed by angle-

dependent factor

suppress high- tail

Q

Dokshitzer, Khoze, Troyan, JPG 17 (1991) 1602.Dokshitzer and Kharzeev, PLB 519 (2001) 199.

1

1d

d

d

d2

2

2

Q

Q

E

mII

LIGHTHEAVY

Dokshitzer

22QQ

2 ])/([

1

Em

Gluonsstrahlung probability

R = 105

Detailed massive calculation confirms this qualitative feature

(Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003)


Heavy-flavour electrons at RHIC(pp baseline)

Heavy-flavour electrons at RHIC(pp baseline)

FONLL calculation: Cacciari, Nason, Vogt, PRL95 (2005) 122001Drell-Yan from: Gavin et al., hep-ph/9502372Comparison: Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326

FONLL: electron spectrum may be ~50% c + ~50% b for 3 < pT < 8 GeV

Drell-Yan component? < 10% up to 10 GeV

Large uncertainty on b/c crossing point in pT: from scales/masses variation it changes from 3 to 9 GeV

PHENIX electron cross section in pp now quite OK also at high pT

PHENIX hep-ex/0508034

PHENIX, hep-ex/0609010

QM06

?

QM06


RAA of c and b electrons at RHICRAA of c and b electrons at RHIC

Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326,

Due to large mass of b quark, theory: electron RAA~0.4

Final data: electron RAA ~ pion RAA ~0.2 at high pT

c

b

c+b

PRL 98, 172301 (2007)

e± from heavy flavor

Djordjevic, Gyulassy, Wicks, nucl-th/0512076

STAR Phys. Rev. Lett. 98 (2007) 192301

PHENIX Phys.Rev.Lett.98 (2007) 172301


RAA of c and b electrons at RHICRAA of c and b electrons at RHIC

C. Salgado, CERN Heavy Ion Forum, Dec 08

Similar results from recent multi-observable 2-analysis including hydro evolution

c+b

c only


QM06RAA of c and b electrons at RHICRAA of c and b electrons at RHIC

nucl-ex/0611018nucl-ex/0611018

(Adil & Vitev)

Other approaches: include elastic E loss (Djordjevic, Gyulassy, Wicks)

collisional dissociation of D/B mesons formed in the medium early after hard scattering (Adil & Vitev)

What have we learnt from Tevatron and RHIC?What have we learnt from Tevatron and RHIC?

Tevatron: c and b production relatively well understood (b better than c...)

theory: leading log resummation (FONLL); parton shower matched to NLO (MC@NLO); accurate treatment of fragmentation (Cacciari et al.: matching of pert. hat and non-pert. fragm. from ee to pp)

experiment: exclusive (or less inclusive) is better (D mesons, BJ/+X), publish what you measure (not only extrapolations)

High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese 13High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese 13


OK? what if we find the same in pp@14TeV? how do we get a realible reference for [email protected]?

What have we learnt from Tevatron and RHIC?What have we learnt from Tevatron and RHIC?

RHIC: heavy-quark (non-phot.) electrons as suppressed as pions, and they do flow (v2, see later)

but the picture is not clear...pp baseline at upper limit of FONLL band (like CDF’s charm)

suppression not understood (small b contribution? large b E loss?)

Need for dedicated detectors (Si trackers) RHIC-II, LHC

High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese 14High-density QCD, Santiago de Compostela, 03.02.2009 Andrea Dainese 14


PHENIX, hep-ex/0609010

c

b

c+b


LayoutLayoutHigh-pT (heavy-flavour) particle production in hadronic collisions –from pp to AA– in factorized QCD





What do we expect?




Novelties at LHC (1): Hard ProbesNovelties at LHC (1): Hard ProbesLHC: large hard cross sections!

Our set of “tools” (probes) becomes richer

quantitatively: qualitatively:• heavy quarks

• + jet correlations• Z0 + jet correlations

bbRHIC

bbLHC

ccRHIC

ccLHC

100

10

LO pQCD by I. Vitev,hep-ph/0212109


Heavy-quark production at the LHCHeavy-quark production at the LHCpp: Important test of pQCD in a new energy domain

Remember the “15-years saga of b production at Tevatron”*

Baseline predictions: NLO (MNR code) in pp + binary scaling (shadowing [EKS98] included for PDFs in the Pb)

e.g. ALICE baseline for charm / beauty: system :

sNN :Pb-Pb (0-5% centr.)

5.5 TeV

p-Pb (min. bias)

8.8 TeV

pp

14 TeV

4.3 / 0.2 7.2 / 0.3 11.2 / 0.5

115 / 4.6 0.8 / 0.03 0.16 / 0.007

0.65 / 0.80 0.84 / 0.90 --

[mb] QQNN

QQtotN

Theoretical uncertainty of a factor 2—3 (next slide)* M.ManganoMNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.

98EKSshadowingC

LHC startup at s = 10 TeV?yields lower by 25%


Theoretical Uncertainties(HERA-LHC Workshop)

Theoretical Uncertainties(HERA-LHC Workshop)

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

Evaluation of theoretical uncertainties

beautycharm

MRST2001 CTEQ6, CTEQ5, CTEQ4, :PDFs

0.0040.0002 2/5.0 GeV 0.55.4

0.110.002 2/5.0 GeV 8.13.1 ,

bRFb

cTRFc

m

mm

CERN/LHCC 2005-014hep-ph/0601164


Model Comparisons(HERA-LHC Workshop)

Model Comparisons(HERA-LHC Workshop)

Compare predictions by several different models

beautycharm

CERN/LHCC 2005-014hep-ph/0601164+ updates (R.Guernane)

General agreement between collinear factorisation based calculations: FO NLO, FONLL, POWHEG, MC@NLO

problem with POWHEG charm?kT factorization (LO MC CASCADE) higher at large pT

VFNS lower at high pT


Energy extrapolation via pQCD?Energy extrapolation via pQCD?

Different systems (pp, p-Pb, Pb-Pb) will have different s values

Results in pp at 14 TeV will have to extrapolated to 5.5 TeV (Pb-Pb energy) to compute, e.g., nuclear modification factors RAA

pQCD: there ratio of results at 14 TeV/5.5 TeV has ‘small’ uncertainty

charm beauty

12% 8%

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

Need to define a strategy!

Anyway, difficult to have pp reference at 5.5 TeV

(only 1 month limited stats, pT reach)


increasing s

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

down to x~10-4 with charm already at y=0

Window on the rich phenomenology of high-density PDFs:

gluon saturation / recombination effects

Novelties at LHC (2): Small xNovelties at LHC (2): Small x

ccgg


Probing small-x gluons with HQs (pp) Probing small-x gluons with HQs (pp)

Large pQCD uncertainties for charm pT0

onset of saturation ?

Two attempts to include non-linear

terms in evolution equationsDGLAP+GLRMQ

BK

indicate charm as a sensitive probe in pp

Eskola et al., NPB660 (2003) 211

Kutak, Kwiecinski, Martin, Stasto

BK: Charm suppression due to non-linear effects

DGLAP: Charm enhancementdue to non-linear effects (GLR-MQ term)

|y| < 1

c(DGLAP+non-linear)c(DGLAP)


Probing small-x gluons with HQs (nuclei)Probing small-x gluons with HQs (nuclei)

Shadowing in pA (AA)

CGC in pA (AA)

Double parton scattering in pA

)/( ppNpPbR collDpPb

c

c

Effect of shadowing on D meson nuclear modification factors at LHC:RAB(pT0) ~ RG

A*RGB at x ~ 2mc/√s ~ 10-3, Q2 ~ 4mc

2 ~ 9 GeV2

EKS98: 0.55 for Pb-Pb at 5.5 TeV 0.75 for p-Pb at 8.8 TeV

EKS98:Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61

€

RGPb (x)




CGC in pA (AA)


)/( ppNpPbR collDpPb

c

c

Effect of shadowing on D meson nuclear modification factors at LHC:RAB(pT0) ~ RG

A*RGB at x ~ 2mc/√s ~ 10-3, Q2 ~ 4mc

2 ~ 9 GeV2

EKS98: 0.55 for Pb-Pb at 5.5 TeV 0.75 for p-Pb at 8.8 TeVEPS08: 0.4 for Pb-Pb at 5.5 TeV 0.6 for p-Pb at 8.8 TeV

EPS08: Eskola, Paukkunen, Salgado, JHEP0807 (2008) 102

to be computed rigorously,

including pT dependence

to be computed rigorously,

including pT dependence

€

RGPb (x)



CGC in pA (AA)


Saturation scale Qs2(x) ~ xg(x)A/RA

2 ~ xg(x)A1/3

At LHC for x~10-4, Qs~1.5-2 GeV > mc

For mT,c~Qs, charm prod. CGC-dominated:• scales with Npart in pA (not Ncoll)• harder pT spectra, since typical kT~Qs~1.5 GeV, while in standard factorization kT~QCD~0.2 GeV


c

c

Kharzeev, Tuchin, NPA 735 (2004) 248 + LHC Predictions Workshop

CGC: very similar RpA for , D, B, ~indep. of pT and rapidity



CGC in pA (AA)


probe “many-body” PDFs

normal and anomalous: different A dep.

signature: events with “tagged” DD (can use D0+e+ or e+e+) and ch. conj.NB: there is a “background” from normal bb events, but it can be estimated from measured single inclusive b cross section

predicted rate: cccc/cc ~ 10% (Treleani et al.)


c

c

Cattaruzza, Del Fabbro, Treleani, PRD 70 (2004) 034022


Heavy Quark Energy Loss at LHCHeavy Quark Energy Loss at LHC

~100 cc pairs and ~5 bb pairs per central Pb-Pb collision

Experiments, with high precision trackers, will measure RAA

for D and B, or for their decay leptons

What can we learn from a comparative quenching study of

massive and massless probes at the LHC?


Heavy Flavour RAA at LHCHeavy Flavour RAA at LHCBaseline: PYTHIA, with EKS98 shadowing, tuned to reproduce c and b pT distributions from NLO pQCD (MNR)

(m/E)-dep. E loss with

MNR: Mangano, Nason, Ridolfi, NPB 373 (1992) 295.

/fmGeV 10025ˆ7ˆ 2* RHICLHC qq

Armesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027. * EKRT Saturation model:Eskola, Kajantie, Ruuskanen, Tuominen, NPB 570 (2000) 379.

(EKS98)(EKS98)

EPS08(guess)

EPS08(guess)


Colour-charge and mass dep. of E loss with Heavy-to-Light ratios at LHC

Colour-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

)()()( )(/)( t

hAAt

BDAAthBD pRpRpR

gq EE mass effect

For 10 < pT < 20 GeV, charm behaves like a m=0 quark,light-flv hadrons come mainly from gluonsRD/h enhancement probes colour-charge dep. of E lossRB/h enhancement probes mass dep. of E loss

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


LHC: Beauty-to-Charm ratio RB/DLHC: Beauty-to-Charm ratio RB/D

Compare c and b: same colour charge

Mass effect Enhancement of factor ~2, independent of (for )

)()()(/ tDAAt

BAAtDB pRpRpR

q/fmGeV 20ˆ 2q

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


Beauty energy loss:W-decay muons as a reference

Beauty energy loss:W-decay muons as a reference

Conesa del Valle, Dainese, Ding, Martinez, Zhou, PLB663 (2008) 202

early measurement for all experiments at the LHC!

single RCP(pT)

medium-sensitive and medium-blind probe in same measurement


Other predictions for RAA at LHCOther predictions for RAA at LHC

Vitev, Adil, “Last Call for LHC Predictions” workshop, 2007

Wicks, Gyulassy, “Last Call for LHC Predictions” worksho, 2007

Radiative+Collisional E lossà la GLV

D

B

D+B

D and B meson formation and dissociation inside the medium

similar to prediction from Armesto et al.


Charm in-medium hadronization: probe of QGP properties?

Charm in-medium hadronization: probe of QGP properties?

Yields of charm hadrons within statistical hadronization model

Rafelski, Kuznetsova, LHC Predictions Workshop 07

Ratio D/Ds as a probe of T at measured s/S

(PYTHIA: 6.92!)

0.13PYTHIA: 0.19

Braun-Muntzinger, Stachel, LHC Predictions Workshop 07


Azimuth. asymmetry: v2 from flowAzimuth. asymmetry: v2 from flow

c: 15-20%

b: 5%

van Heese, Rapp, Greco, LHC Predictions Workshop 07

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

Model: mult. scattering in expanding QGP ( elliptic flow)

hadronization via coalescence + fragmentation


Azimuth. asymmetry: v2 from E lossAzimuth. asymmetry: v2 from E lossv2 of D and B mesons in non-central collisions tests

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

Model: Radiative E loss (BDMPS)

RHIC

Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326 + LHC Predictions Workshop 07

c: 5-10%

LHC


LayoutLayoutHigh-pT (heavy-flavour) particle production in hadronic collisions –from pp to AA– in factorized QCD





What do we expect?




Tracker TPC (>100) + Si (6) Si (11) Si (16)

Pixel layers

Inner radius

Pixel cell (rx z)

2

4 cm

50x425 m2

3 (+ 6 endcaps)

5 cm

50x400 m2

3 (+ 6 endcaps)

4.3 cm

100x150 m2

Si thickness (x/X0) 7% 30% 20%

d0 res at 1 (10) GeV/c

60 (15) m 80 (15) m 80 (15) m

B field (T) 0.5 2 4

Muon ID -4<<-2.5, pT>1 GeV ||<2.4, pT>3 ||<2.4, pT>3.5

Electron ID ||<0.9, “ ||<2.5, pT>? ||<3, pT>10

Heavy flavour capabilities:tracking, vertexing, lepton IDHeavy flavour capabilities:

tracking, vertexing, lepton ID

d0trackprimary

vertex


Heavy-flavour capabilities:acceptances & tracking resolutions

Heavy-flavour capabilities:acceptances & tracking resolutions

ALICE(c/b)

ATLAS/CMS(b) LHCb

(b)

-2 0 2 4 61

10

100

1 year pp 14 TeV @ nominal lumin.

pT

of

Q-h

ad

ron

[G

eV]

of Q-hadron

ALICE(b)(c)

ALICE(c/b)

ATLAS/CMS(b) LHCb

(b)

-2 0 2 4 61

10

100


pT

of

Q-h

ad

ron

[G

eV]

of Q-hadron

ALICE(b)(c)

ALICE(c/b)

ATLAS/CMS(b) LHCb

(b)

-2 0 2 4 61

10

100


pT

of

Q-h

ad

ron

[G

eV]

of Q-hadron

ALICE(b)(c)

ALICE(c/b)

ATLAS/CMS(b) LHCb

(b)

-2 0 2 4 61

10

100


pT

of

Q-h

ad

ron

[G

eV]

of Q-hadron

ALICE(b)(c)

HERA-LHC WorkshopCERN/LHCC 2005-014hep-ph/0601164

A.Dainese (ALICE)M.Smizanska (ATLAS)

C.Weiser (CMS)U.Uwer (LHCb)


Open heavy-flavour in ALICEOpen heavy-flavour in ALICE

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

understudy

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

understudy

D0K in Pb-PbD+K in pp

Be +X in Pb-Pb


Heavy-to-light ratios in ALICEHeavy-to-light ratios in ALICE

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

)()()(/ thAAt

DAAthD pRpRpR probes colour-charge dep.

of QCD energy loss

€

RB / D (pt ) = RAAe from B(pt ) RAA

e from D(pt )

probes mass dep.of QCD energy loss

E loss calc.: Armesto, et al.Predictions also by Wicks, et al.


SummarySummaryLHC: heavy quarks factory!Heavy quarks as probes of high-density QCD

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

pPb reference neededcan we live without pp at the Pb-Pb energy?

Experiments getting ready all crucial detectors (Si trackers, lepton ID) already commissionedthorough calibration and alignment with cosmic runs

Stray particle from LHC beam2 interacts in ALICE pixels [Sept 11, 08]


Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

442 days to LHC startup!

Hard Probes 2008 14.06.08 Andrea Dainese

ISMD 2008, DESY Hamburg, 18.09.08 Andrea Dainese

after all, maybe we don’t care too much

about the LHC starting ...

after all, maybe we don’t care too much

about the LHC starting ...



EXTRA SLIDESEXTRA SLIDES


LHC running conditionsLHC 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


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

D+D0


Beauty in the barrel:displaced single electrons

Beauty in the barrel:displaced single electrons

PrimaryVertex B

e

Xd0

rec. track

• ALICE has excellent electron identification capabilities (TRD + TPC)

• Displaced electrons from B decays can be tagged by an impact parameter cut

electron


Beauty in the barrel: displaced J/ee

Beauty in the barrel: displaced J/ee

• Standard method for b prod. meas. at the Tevatron• Displaced di-electrons (TPC,TRD) from J/ from B decays

tagged by an impact parameter cut (ITS)

t

Jxy p

ML /

totalbackgroundall J/J/ from B

J/ pseudoproper decay time (pt>0)

in progress

Lxy

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Heavy Quarks at the LHC

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