introduzione alla fisica degli heavy flavour nelle collisioni nucleari ultrarelativistiche

11

Introduzione alla fisica degli Introduzione alla fisica degli heavy flavour nelle collisioni heavy flavour nelle collisioni nucleari ultrarelativistichenucleari ultrarelativistiche

Federico AntinoriFederico Antinori(INFN, Padova & CERN, Ginevra)(INFN, Padova & CERN, Ginevra)

FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

http://en.wikipedia.org/wiki/Image:CERN_logo_400x400.gif


22

LHC is a Heavy Flavour Machine!LHC is a Heavy Flavour Machine! cccc and and bbbb rates rates

ALICE PPR (NTLO + shadowing)ALICE PPR (NTLO + shadowing)

115 115 // 4.64.60.65 0.65 // 0.850.856.6 6.6 // 0.20.2Pb-Pb 5.5 TeV (5% Pb-Pb 5.5 TeV (5% cent)cent)

0.160.16 // 0.0070.00711 // 1111.211.2 // 0.50.5 pp 14 TeVpp 14 TeVshadowingshadowingsystemsystem NN x-sect (mb)NN x-sect (mb) total multiplicitytotal multiplicity

PbPbpp

PbPbpp

cc bbPbPb/pp PbPb/pp

33

Probing the medium with heavy Probing the medium with heavy flavoursflavours

c, b produced in early stages of collision, then c, b produced in early stages of collision, then conserved (neglecting annihilation)conserved (neglecting annihilation)production quantitatively under control in pQCDproduction quantitatively under control in pQCD ideal probes of bulk, strongly interacting phaseideal probes of bulk, strongly interacting phase energy loss? energy loss?

thermal production?thermal production?

no extra production at hadronizationno extra production at hadronization ideal probes of fragmentation ideal probes of fragmentation independent string fragmentation vs recombinationindependent string fragmentation vs recombination


Corso in due partiCorso in due parti Parte prima: Parte prima:

introduzione introduzione heavy flavour in collisioni elementariheavy flavour in collisioni elementari

Parte seconda: Parte seconda: heavy flavour in collisioni nucleo-nucleoheavy flavour in collisioni nucleo-nucleo


44

Parte prima : Parte prima : introduzione,introduzione,heavy flavour heavy flavour

in collisioni elementariin collisioni elementari

55


66

Heavy Flavour Heavy Flavour DecaysDecays


77

Some zoology...Some zoology... Lower mass heavy flavour hadrons decay weakly Lower mass heavy flavour hadrons decay weakly

~ ps~ ps cc ~ 100’s µm ~ 100’s µm

weakly decaying states from PDG 2006 summary tables:weakly decaying states from PDG 2006 summary tables:

µm 21c MeV 2698m )(

µm 34c MeV 2472m )(

µm 132c MeV 2466m )(

µm 60c MeV 2285m )(

µm 147c MeV 1968m )(

µm 123c MeV 1865m )(

µm 312c MeV 1869m )(

0

0

0

ssc

dsc

usc

udc

scD

ucD

dcD

c

c

c

c

s

µm 368c MeV 5624m )(

µm 200001c GeV 6.4 m )(

µm 438c MeV 5370m )(

µm 460c MeV 5279m )(

µm 501c MeV 5279m )(

0

0

0

udb

bcB

bsB

bdB

buB

b

c

s


88

Impact parameter ~ cImpact parameter ~ c In UR limit In UR limit bb ~ Lorentz invariant: ~ Lorentz invariant:

... so b ~ independent of ... so b ~ independent of

if cos if cos CMCM distribution is flat: distribution is flat:

so, in space,so, in space,

in projection:in projection:

so:so:

primary vertexprimary vertex

decay vertexdecay vertex

decay length = Ldecay length = L

impact parameter =

impact parameter = bb

,

1e)proper tim(

CMCM

LAB

CMLAB

ctctLb

tctL

2)sin(

21

)sin(21)(

0

CMCMCMCM

CMCMCMCM

d

ddf bdbd

df

bd

2cos1

;1)(

cos

2/

2/

cc CM 2b

yy

xxdd

bb

cd


99

Weak decays of charmWeak decays of charm typically:typically:

large branching ratio to kaonslarge branching ratio to kaons:: DD++: :

DD++ K K--+X BR ~ 28 %+X BR ~ 28 % ““golden” channel: Dgolden” channel: D++ K K--++++ BR ~ 9% BR ~ 9%

DD00:: DD00 K K--+X BR ~ 50%+X BR ~ 50% ““golden” channels: Dgolden” channels: D00 K K--++ BR ~ 4% ; D BR ~ 4% ; D00 K K--++++-- BR ~ 7% BR ~ 7%

WW±± branchings: branchings:

large semileptonic branching ratio, varies with heavy flavour large semileptonic branching ratio, varies with heavy flavour particle, typical ~ 10%particle, typical ~ 10%~ 10% heavy flavour hadrons give in final state an e~ 10% heavy flavour hadrons give in final state an e±± (and ~ 10% a µ (and ~ 10% a µ±±))

(and with a respectable p(and with a respectable pTT...)...)

cc s’s’

WW++

dsdss CC 22.097.0sincos'

cc s’s’

WW++uud’d’

ee++

ee

µµ++

µµ

bb cc

WW--

(similarly: )(similarly: )

CC = “Cabibbo angle” = “Cabibbo angle”


1010

Standard experimental toolsStandard experimental tools Silicon vertex detectors:Silicon vertex detectors:

so: tracks from heavy flavour weak decays typically “miss” so: tracks from heavy flavour weak decays typically “miss” primary vertex by ct ~ 100’s µmprimary vertex by ct ~ 100’s µm

impact parameter resolutions of typical heavy flavour impact parameter resolutions of typical heavy flavour apparatus ~ 10’s µmapparatus ~ 10’s µm

ee±± and/or µ and/or µ ±± identification identification

charged kaon identificationcharged kaon identification

primary vertexprimary vertex

decay vertexdecay vertex

decay length = Ldecay length = L

impact parameter =

impact parameter = bb

WA92:WA92:Si µstripsSi µstrips

[Adamovich et al.: NIM A 379 (1996) 252][Adamovich et al.: NIM A 379 (1996) 252]FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

1111

Heavy Flavour Heavy Flavour Production in Production in QCDQCD


1212

Heavy Flavour hadro-production in Heavy Flavour hadro-production in pQCDpQCD

Factorization:Factorization:

)()( // bBbaAa xGxG )ˆ(ˆ sxxs baccab )(/ zD cD DXAB

XDBA hadronhadron hadronhadron charmedcharmed

hadronhadron

cross-section at parton levele.g.:

parton distribution functionsxa = momentum fraction of parton a in hadron A

fragmentationz = fraction of c momentum to hadron D

cross-section at hadron level

a=q

b=q Q

Q

(at sufficiently large Q(at sufficiently large Q22))


1313

factorization implies:factorization implies: PDFs can be measured with one reaction... PDFs can be measured with one reaction...

say: Drell-Yan: A+B say: Drell-Yan: A+B e e++ee- - + X + X ... and used to calculate a different one ... and used to calculate a different one

say: heavy-flavour productionsay: heavy-flavour production fragmentation independent of the reaction (e.g.: same in pp, fragmentation independent of the reaction (e.g.: same in pp,

ee++ee--) )

)()( // bBbaAa xGxG )ˆ(ˆ sxxs baccab )(/ zD cD DXAB


1414

Parton Distribution FunctionsParton Distribution Functions

PDFs vary depending on PDFs vary depending on momentum transfer scale momentum transfer scale QQ22

Intuitively:Intuitively:higher Qhigher Q22 -> higher resolution -> higher resolutionhigh-x parton -> lower-x high-x parton -> lower-x partonspartons

The QThe Q22 evolution of the evolution of the PDFs can be calculated in PDFs can be calculated in pQCD pQCD Altarelli-Parisi evolutionAltarelli-Parisi evolution

(DGLAP)(DGLAP)FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

1515

Leading-order (LO)Leading-order (LO) Relevant diagrams: pair creationRelevant diagrams: pair creation

qq qq QQ QQ (quark-antiquark annihilation)(quark-antiquark annihilation)

gggg QQ QQ (gluon-gluon fusion)(gluon-gluon fusion)

q

q Q

Q

Q

Qg

g Q

Qg

gQ

Qg

g


1616

A few resultsA few results the partonic cross-section decreases with energythe partonic cross-section decreases with energy

faster for qq than for gg (which therefore is expected to dominate, faster for qq than for gg (which therefore is expected to dominate, except near threshold)except near threshold)

the parton luminosities near threshold increase with energy, the parton luminosities near threshold increase with energy, the cross section increases with the energy of the hadron-hadron the cross section increases with the energy of the hadron-hadron collisioncollision

the pair cross section is proportional to:the pair cross section is proportional to:

y (y): rapidity of Q (Q)y (y): rapidity of Q (Q)

Q and Q therefore expected to be close in yQ and Q therefore expected to be close in y

Experimentally: EHS, 360 GeV Experimentally: EHS, 360 GeV --p p DDX DDX

2)]cosh(1[1

yy

z

z

pEpEy log2

1

[EHS: PLB 123 (1983) 98]FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

1717

Next-To-Leading-Order (NTLO)Next-To-Leading-Order (NTLO) in absolute value, LO cross sections are typically in absolute value, LO cross sections are typically

underestimated by factor 2.5 - 3 (“K factor”)underestimated by factor 2.5 - 3 (“K factor”)

at NTLO: additional diagrams, such as:at NTLO: additional diagrams, such as:

Q

Q

Q

Q

Q

Q

higher order corrections to pair creationhigher order corrections to pair creation

flavour excitationflavour excitation

gluon splittinggluon splitting


1818

the agreement with experiment for the total cross-the agreement with experiment for the total cross-section is good (within large bands...)section is good (within large bands...) e.g.: charm cross section at fixed target:e.g.: charm cross section at fixed target:

[Mangano: hep-ph/9711337]FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

1919

results depend on the values of:results depend on the values of: mmcc, µ, µRR (renormalization scale), µ (renormalization scale), µFF (factorization scale) (factorization scale)

the result of an exact calculation would be the result of an exact calculation would be independent of the choice of the scale parameters µindependent of the choice of the scale parameters µRR, , µµFF the residual scale dependence is a measure of the accuracy the residual scale dependence is a measure of the accuracy

of the calculationof the calculation e.g.: for b production at Tevatron (µe.g.: for b production at Tevatron (µRR=µ=µFF=µ):=µ):

[Mangano: hep-ph/9711337]


2020

it is important to match the PDFs with the order of it is important to match the PDFs with the order of the calculation. the calculation.

e.g. one must avoid double counting:e.g. one must avoid double counting: at LO:at LO:

at NTLO:at NTLO:

“intrinsic flavour”

“flavour excitation”Q

Q

QQ


2121

Heavy Flavour in Heavy Flavour in p/p/-A-A


2222

Nuclear shadowingNuclear shadowing PDFs in the nucleus different from PDFs in free protonPDFs in the nucleus different from PDFs in free proton

R = ratio of nuclear to nucleon PDFs R = ratio of nuclear to nucleon PDFs from Deep Inelastic Scattering (efrom Deep Inelastic Scattering (e--+p; e+p; e--+A), Drell-Yan (p+p, p+A -> +A), Drell-Yan (p+p, p+A -> l l ++l l --

+X)+X)

e.g.: e.g.: R for gluons vs R for gluons vs gluon momentum gluon momentum fraction fraction xxfrom EKS parametrization from EKS parametrization [Eskola et al.: EPJ C9 (1999) 61][Eskola et al.: EPJ C9 (1999) 61]

typical typical xx for cc production ( for cc production (yy 0)0) xx 10 10-1-1 @ SPS @ SPS xx 10 10-2-2 @ RHIC @ RHIC xx a few 10 a few 10-4-4 @ LHC @ LHC

shadowing

antishadowing

SPSSPSRHICRHIC

LHCLHC


2323

Nuclear dependenceNuclear dependence From pQCD one expects the cross section for production off From pQCD one expects the cross section for production off

nuclei to increase like number of nucleon-nucleon collisions nuclei to increase like number of nucleon-nucleon collisions (“binary collision scaling”) (“binary collision scaling”)

proportional to number of nucleons (for min. bias collisions):proportional to number of nucleons (for min. bias collisions):

modulo shadowing effects, expected to be smallmodulo shadowing effects, expected to be small

Experimentally: not far... e.g. WA82: Experimentally: not far... e.g. WA82: D production in D production in --+W/Si at SPS (340 GeV beam momentum)+W/Si at SPS (340 GeV beam momentum) (relatively) central production(relatively) central production

AQQQQ

A

)()(

0 with =1

06.092.0 spppx z

zzF2/ max 24.0 @ Fx

“Feynman’s x”FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

2424

Caveats...Caveats... i) i) = 1 does not work down to pp! = 1 does not work down to pp!

e.g.: MacDermott & Reucroft e.g.: MacDermott & Reucroft [PLB 184 (1987) 108] compare pA results compare pA results with earlier hydrogen data from NA27, good agreement using:with earlier hydrogen data from NA27, good agreement using:

note: similar situation for light flavours! note: similar situation for light flavours! systematic study by Barton et al. systematic study by Barton et al. [PRD 27 (1983) 2580],[PRD 27 (1983) 2580], for various for various reactions at 100 GeV FT reactions at 100 GeV FT e.g.: central for production of e.g.: central for production of , K, p from p on nuclear targets:, K, p from p on nuclear targets:

ccpp

cc 0

AK ccpp

ccpA 0 5.1 ,1 0 K

6.0 25.10 Kwith


2525

ii) lower ii) lower at large x at large xFF?? early beam dump experiments, sensitive at large xearly beam dump experiments, sensitive at large xFF (max acceptance for x (max acceptance for xFF

0.5)0.5)(in tracking experiments, typically max. acceptance for x(in tracking experiments, typically max. acceptance for xFF 0.2) 0.2)e.g. WA78 [Cobbaert et al.: PLB 191 (1987) 456]e.g. WA78 [Cobbaert et al.: PLB 191 (1987) 456] for muons escaping dump (for muons escaping dump (--A at 320 GeV FT ):A at 320 GeV FT ):

note: note: is known to decrease is known to decreasewith xwith xFF for light hadrons for light hadrons

06.083.0)(

08.076.0)(

4.0Fx

[Barton et al.: PRD 27 (1983) 2580][Barton et al.: PRD 27 (1983) 2580]


2626

Heavy Flavour Heavy Flavour FragmentationFragmentation


2727

FragmentationFragmentation String fragmentation model:String fragmentation model:

(e.g. [PYTHIA (e.g. [PYTHIA hep-ph/0308153]) as coloured quarks fly away, energy is stored as coloured quarks fly away, energy is stored

in the field:in the field:

above a certain distance it is cheaper to above a certain distance it is cheaper to break the string by creating a new qq pair break the string by creating a new qq pair than to keep increasing the distancethan to keep increasing the distance

the string snaps, e.g.: the heavy quark ends the string snaps, e.g.: the heavy quark ends up “hadronising” together with a light up “hadronising” together with a light antiquarkantiquark

the newly created quarks are of course lightthe newly created quarks are of course light estimated ratios:estimated ratios:

u : d : s : c u : d : s : c 1 : 1 : 0.3 : 10 1 : 1 : 0.3 : 10-11-11

no heavy flavour production in string no heavy flavour production in string breaking!breaking!

dV 1 GeV/fm


2828

Fragmentation functionFragmentation function c c D, D takes fraction D, D takes fraction zz of c momentum of c momentum

fragmentation function: Dfragmentation function: DD/cD/c((zz)) depends only on fraction zdepends only on fraction z e.g.:e.g.:

2/ )]1/(/11[1)(

zzzzD cD

Peterson

zzzD cD )1()(/ Colangelo-Nason

Peterson ( = 0.015)

Colangelo-Nason ( = 0.9, =6.4)

e.g.: (parameters from fits to charm production at LEP)


2929

How to measure the fragmentation function?How to measure the fragmentation function? we don’t measure the original we don’t measure the original QQ momentum ... momentum ... but in ebut in e++ee-- we do know the we do know the QQ momentum (by energy momentum (by energy

conservation!)conservation!) e.g.:e.g.:

fragmentation functions are usually extracted from efragmentation functions are usually extracted from e++ee-- measurements and then used for other collisionsmeasurements and then used for other collisions

e-

Q

Q

e+

Z0


3030

e.g.: fits to charm x = 2E/e.g.: fits to charm x = 2E/s distributions in es distributions in e++ee--::[Cacciari & Greco: PRD55 (1997) 7134][Cacciari & Greco: PRD55 (1997) 7134]

very similar parameters at the two very similar parameters at the two energies (as expected)energies (as expected)

s = 10.6 GeV (ARGUS) s = 91.2 GeV (OPAL)

Peterson fragmentation

= 0.015 (OPAL) = 0.019 (ARGUS)


3131

like for the PDFs, the fragmentation function has to be like for the PDFs, the fragmentation function has to be matched to order of pQCD calculationmatched to order of pQCD calculation e.g. at NTLO a e.g. at NTLO a QQ can radiate: can radiate:

so final energy before so final energy before non-perturbative part of non-perturbative part of fragmentation lower than at LO fragmentation lower than at LO

harder fragmentation at NTLOharder fragmentation at NTLO at NTLO: at NTLO: 0.015 0.015 at LO: at LO: 0.06 0.06

(e.g.: (e.g.: [Cacciari & Greco: PRD55 (1997) 7134][Cacciari & Greco: PRD55 (1997) 7134]))

Peterson fragmentation

= 0.015 (NTLO) = 0.06 (LO)

Q

Q


3232

D* decays, DD* decays, D00(cu) / D(cu) / D++(cd) (cd) ratioratio


3333

D* decaysD* decays Most of the D mesons (from spin counting, ~ 75%) are not Most of the D mesons (from spin counting, ~ 75%) are not

directly produced at hadronization, but in D* decaysdirectly produced at hadronization, but in D* decays DD±±, D, D00 J=0J=0 DD*±*±, D, D*0*0 J=1J=1

Due to fine tuning of the values of the masses:Due to fine tuning of the values of the masses: m(Dm(D±±) + m() + m(00) < m(D) < m(D*±*±) ) m(Dm(D00) + m() + m(±±) < m(D) < m(D*±*±) ) m(Dm(D00) + m() + m(00) < m(D) < m(D*0*0))

but...but... m(Dm(D±±) + m() + m(±±) > m(D) > m(D*0*0))

... the light quark content of charged D is preserved also in case ... the light quark content of charged D is preserved also in case of resonance decays:of resonance decays: a Da D00(cu) can originate from either D(cu) can originate from either D*0*0(cu) or D(cu) or D*+*+(cd)(cd) a Da D++(cd) can only originate from a D(cd) can only originate from a D*+*+(cd)(cd)


3434

DD00/D/D++ ratio at LEP ratio at LEP DD*0*0 and D and D*+*+ both decay strongly into D’s, but: both decay strongly into D’s, but:

DD*+*+ can decay to both D can decay to both D00 and D and D++

DD*0*0 can only decay to D can only decay to D00

From spin degeneracy one expects:From spin degeneracy one expects:DD00 : D : D++ : D : D*0*0 : D : D*+*+ = 1 : 1 : 3 : 3 = 1 : 1 : 3 : 3

... and therefore a large D... and therefore a large D00/D/D++ ratio ratio using the experimental branching ratios:using the experimental branching ratios:

but experimentally, at LEP:but experimentally, at LEP:

08.3030.3231130.6831

)()()()(

0*0***

00*0*0**00

DDBRDDDBRDDDDBRDDDBRDD

DD

prompt

prompt

3.20

DD

[ALEPH: EPJ C16 (2000) 597][ALEPH: EPJ C16 (2000) 597]


3535

Heavy Flavour at Heavy Flavour at TevatronTevatron


3636

Beauty at TevatronBeauty at Tevatron Discrepancy between pQCD and data seems to have disappeared...Discrepancy between pQCD and data seems to have disappeared...

from...from...

a factor 5.5 (but only 1.6 a factor 5.5 (but only 1.6 ...) ...) to...to... [CDF: PRL 68 (1992) 3403][CDF: PRL 68 (1992) 3403]

Run 0Run 0

Run IIRun II

[Cacciari et al: JHEP 0407 (2004)][Cacciari et al: JHEP 0407 (2004)]

Spectrum of J/Spectrum of J/ from secondary B decays from secondary B decays


3737

From run I on, important improvements in accuracy:From run I on, important improvements in accuracy: experiment (vertex detectors, high statistics)experiment (vertex detectors, high statistics) prediction (post-HERA PDF sets)prediction (post-HERA PDF sets)

Levels of stability over time:Levels of stability over time:

no large room for new physics any more...no large room for new physics any more... for more see, e.g.: for more see, e.g.:

[Cacciari et al: JHEP 0407 (2004) 033, Cacciari: hep-ph/0407187, Mangano: hep-ph/0411020][Cacciari et al: JHEP 0407 (2004) 033, Cacciari: hep-ph/0407187, Mangano: hep-ph/0411020]

DataData PredictionsPredictions

from [Cacciari et al: JHEP 0407 (2004) 033]from [Cacciari et al: JHEP 0407 (2004) 033]


3838

What about charm?What about charm? Nice data from CDF run IINice data from CDF run II

[CDF: Phys.Rev.Lett. 91 (2003) 241804][CDF: Phys.Rev.Lett. 91 (2003) 241804]

roughly in agreement with full roughly in agreement with full pQCD calculationpQCD calculation(though prediction somewhat (though prediction somewhat low)low)

A curiosity (?):A curiosity (?):good agreement between data good agreement between data and prediction for bare quarkand prediction for bare quark

[Vogt: talk at SQM 2004][Vogt: talk at SQM 2004]


Parte seconda : Parte seconda : heavy flavour heavy flavour

in collisioni nucleo-nucleoin collisioni nucleo-nucleo

3939


4040

Charm and beauty: ideal probesCharm and beauty: ideal probes study medium with probes of known colour charge study medium with probes of known colour charge

and mass and mass e.g.: energy loss by gluon radiation expected to be:e.g.: energy loss by gluon radiation expected to be: parton-specific: stronger for gluons than quarks (colour parton-specific: stronger for gluons than quarks (colour

charge)charge) flavour-specific: stronger for lighter than for heavier quarks flavour-specific: stronger for lighter than for heavier quarks

(dead-cone effect)(dead-cone effect) study effect of medium on fragmentation (no extra study effect of medium on fragmentation (no extra

production of c, b at hadronization)production of c, b at hadronization) independent string fragmentation vs recombinationindependent string fragmentation vs recombination e.g.: De.g.: D++

ss/D/D++

+ measurement important for quarkonium physics+ measurement important for quarkonium physics open QQ production natural normalization for quarkonium open QQ production natural normalization for quarkonium

studiesstudies B meson decays non negligible source of non-prompt J/B meson decays non negligible source of non-prompt J/FA - Quark Matter Italia - Roma Sanità - 24 aprile

2009

4141

Heavy flavour production in AAHeavy flavour production in AA binary scaling: binary scaling:

can be broken by:can be broken by: initial state effects (modified PDFs)initial state effects (modified PDFs)

shadowingshadowing kkTT broadening broadening gluon saturation (colour glass)gluon saturation (colour glass)

(concentrated at lower p(concentrated at lower pTT))

final state effectsfinal state effects (modified fragmentation) (modified fragmentation) parton energy lossparton energy loss violations of independent fragmentation (e.g. quark recombination) violations of independent fragmentation (e.g. quark recombination)

(at higher p(at higher pTT))

ppAA dcollNd


4242

What do we know from the SPS?What do we know from the SPS? Intermediate mass dimuon Intermediate mass dimuon

excess in central Pb-Pb at SPS excess in central Pb-Pb at SPS (NA50)(NA50)

Main known sources in that Main known sources in that region: Drell-Yan and charm region: Drell-Yan and charm pairspairs

M (GeV/c2)

centralcollisions


4343

Study of the I.M. excess in NA60Study of the I.M. excess in NA60 Fit weighted impact parameter distributionFit weighted impact parameter distribution

prompt from J/prompt from J/ψψ dimuons, charm from PYTHIA dimuons, charm from PYTHIA requires > 2 x expected D-Y to fit datarequires > 2 x expected D-Y to fit data

6500 A, 2match < 3

sensitivity to assumption on cc psensitivity to assumption on cc pTT, , ΔφΔφ extracted value of cc cross section ~ 2 – 3 larger than extrap.extracted value of cc cross section ~ 2 – 3 larger than extrap.

but compatible with extrapolation from NA50 p-Abut compatible with extrapolation from NA50 p-A

NA60

H.Woehri and C.Lourenco, Phys.Rep. 433 (2006) 127-180


4444

Heavy Flavour @ RHIC: Heavy Flavour @ RHIC: experimental techniquesexperimental techniques


4545

Non-photonic electronsNon-photonic electrons Identified electron spectraIdentified electron spectra

STAR: dE/dx in TPC + TOF at low pSTAR: dE/dx in TPC + TOF at low pTT, EMC at high p, EMC at high pTT PHENIX: combined RICH and E/p (with E from EM cal)PHENIX: combined RICH and E/p (with E from EM cal)

Rejection of non-heavy-flavour electronsRejection of non-heavy-flavour electrons Main source of electrons: “photonic”Main source of electrons: “photonic”

ee++ee-- conversions conversions Dalitz decays Dalitz decays 00 e e++ee-- Dalitz decays Dalitz decays e e++ee--

STAR:STAR: rejected by full invariant mass analysis of erejected by full invariant mass analysis of e++ee-- combinations combinations

PHENIX:PHENIX: estimated by simulation and subtracted (“cocktail method”)estimated by simulation and subtracted (“cocktail method”) measured by “converter method” and subtractedmeasured by “converter method” and subtracted

Other sources of non-charm electrons:Other sources of non-charm electrons: ,,,,, K decays, K decays

estimated by sim. and subtracted (in both STAR and PHENIX)estimated by sim. and subtracted (in both STAR and PHENIX)

(“internal conversions”)(“internal conversions”)


4646

Reconstructed decays (STAR)Reconstructed decays (STAR) DD00 K K

tracks from TPCtracks from TPC K, K, identification from dE/dx identification from dE/dx no separation of D decay vertexno separation of D decay vertex large combinatiorial background large combinatiorial background

evaluated by event mixing and evaluated by event mixing and subtractedsubtracted

residual background, subtracted residual background, subtracted with linear fitwith linear fit


4747

Low pLow pTT muons (STAR) muons (STAR)1.1. in TPC (dE/dx)in TPC (dE/dx)

2.2. in TOFin TOF

3.3. fit to impact fit to impact parameter parameter distributiondistribution charm charm should ~ should ~

point to primary...point to primary...

[C Zhang (STAR) QM06]


4848

Experimental statusExperimental status


4949

PHENIX ppPHENIX pp Excess wrt FONLL:Excess wrt FONLL:

Similar situation also in CDF:Similar situation also in CDF:

[A. Adare et al. (PHENIX) Phys.Rev.Lett. 97 (2006) 252002]

Ratio: 1.72 0.02 (stat) 0.19 (sys)(0.3 < pT < 9.0 GeV/c)

D0

[D. Acosta et al. (CDF) PRL 91 (2003) 241804]FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

5050

STAR v PHENIX ppSTAR v PHENIX pp ~ a factor 2 discrepancy~ a factor 2 discrepancy

hep-ex/0609010

[J. Lajoie (PHENIX) QM06]


5151

STAR dAu, AuAuSTAR dAu, AuAu Internal consistencyInternal consistency

[M. Calderon (STAR) QM06]


5252

STAR v PHENIX dAu, AuAuSTAR v PHENIX dAu, AuAu Discrepancy pretty “stable” v collision system, channel, pDiscrepancy pretty “stable” v collision system, channel, pTT

0,0 0,5 1,0 1,5 2,0 2,5 3,010-5

10-4

10-3

10-2

10-1

100

1/(2N

evp T)d

2 N/d

p Td y [(G

eV/c

)-2]

pT [GeV/c]

STAR Combined fit MB , electrons and D-mesons

Phenix MB Au+Au data

looks like something very basic...looks like something very basic... of course then Rof course then RAAAA not too different... not too different... [A. Suaide QM06]


5353

STAR v PHENIX: RSTAR v PHENIX: RAAAA RRAAAA of non-photonic electrons of non-photonic electrons

[A. Suaide QM06]

similar picture from STAR and PHENIXsimilar picture from STAR and PHENIXFA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

5454

InterpretationsInterpretations


5555

Theoretically...Theoretically...

Energy loss for heavy flavours is expected to be reduced:Energy loss for heavy flavours is expected to be reduced:i)i) Casimir factorCasimir factor

light hadrons originate from a mixture of gluon and quark jets, light hadrons originate from a mixture of gluon and quark jets, heavy flavoured hadrons originate from quark jets heavy flavoured hadrons originate from quark jets

CCRR is 4/3 for quarks, 3 for gluons is 4/3 for quarks, 3 for gluons ii)ii) dead-cone effectdead-cone effect

gluon radiation expected to be suppressed for gluon radiation expected to be suppressed for < M < MQQ/E/EQQ[Dokshitzer & Karzeev,[Dokshitzer & Karzeev, Phys. Lett. Phys. Lett. B519B519 (2001) 199] (2001) 199][Armesto et al., Phys. Rev. D69 (2004) 114003][Armesto et al., Phys. Rev. D69 (2004) 114003]

2 ˆ LqCE Rs

Casimir coupling factortransport coefficient of the medium

average energy loss distance travelled in the medium

R.Baier et al., Nucl. Phys. B483 (1997) 291 (“BDMPS”)


5656

Experimentally...Experimentally...

non ph. el. ~ as non ph. el. ~ as suppressed as light suppressed as light hadronshadrons

use of high density use of high density (qhat), introduction of (qhat), introduction of elastic (in addition to elastic (in addition to radiative) energy loss... radiative) energy loss... not enoughnot enough

high qhat and no beauty high qhat and no beauty electrons does betterelectrons does better

[B.I. Abelev et al (STAR): nucl-ex/0607012]


5757

How much beauty?How much beauty? high phigh pTT region expected region expected

to be beauty-dominated to be beauty-dominated but how “high”?but how “high”?

[M. Cacciari et al.: PRL 95 (2005) 122001]

not easy to disentangle c/b not easy to disentangle c/b contributions to RHIC non ph. contributions to RHIC non ph. el. samples (no heavy flavour el. samples (no heavy flavour vertex detectors in RHIC vertex detectors in RHIC experiments)experiments)

[A. Suaide QM06]


5858

E loss being understood?E loss being understood?

DongJo Kim (PHENIX)FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

5959

another sobering caveat…another sobering caveat… Relative abundances in charm sector also important:Relative abundances in charm sector also important:

c/D

(e c)/(e D)

DD00 DD DDss++ cc

++

BR (XBR (Xe) e) in %in %

17.2 17.2 1.91.9

66..71 71 0.290.29

8 +6-58 +6-5 4.5 4.5 1.7 1.7

Sebastien Gadrat

(see also P Sorensen & X Dong, PRC 74 (2006) 024902)

and what about Dand what about Dss?? s enhancement!s enhancement!

e.g.: e.g.: ΛΛcc/D may change /D may change from pp to AAfrom pp to AA


6060

Vertex Detectors!Vertex Detectors! need less indirect measurementneed less indirect measurement

full reconstruction of charm decays!full reconstruction of charm decays! get rid of b/c ambiguitiesget rid of b/c ambiguities study relative abundances in charm sectorstudy relative abundances in charm sector

Silicon Pixels in ALICE (+ ATLAS, CMS)Silicon Pixels in ALICE (+ ATLAS, CMS)

Silicon Vertex upgrades in STAR, PHENIXSilicon Vertex upgrades in STAR, PHENIX


6161

Track Impact ParameterTrack Impact Parameter

track impact parameter (dtrack impact parameter (d00): ): separation of secondary tracks separation of secondary tracks from HF decays from primary vtxfrom HF decays from primary vtx


6262

PIXEL CELL

z: 425 m

r: 50 m

Two layers:r = 4 cmr = 7 cm

9.8 M

e.g.: D0 K-+

Impact parameter measurement in Impact parameter measurement in ALICEALICE

expected dexpected d00 resolution resolution (() )

ALICE Silicon PixelsALICE Silicon Pixels


6363

LHC is a Heavy Flavour Machine!LHC is a Heavy Flavour Machine! cccc and and bbbb rates rates

ALICE PPR (NTLO + shadowing)ALICE PPR (NTLO + shadowing)

115 115 // 4.64.60.65 0.65 // 0.850.856.6 6.6 // 0.20.2Pb-Pb 5.5 TeV (5% Pb-Pb 5.5 TeV (5% cent)cent)

0.160.16 // 0.0070.00711 // 1111.211.2 // 0.50.5 pp 14 TeVpp 14 TeVshadowingshadowingsystemsystem NN x-sect (mb)NN x-sect (mb) total multiplicitytotal multiplicity

PbPbpp

PbPbpp

cc bbPbPb/pp PbPb/pp


6464

large cross-sectionslarge cross-sections low-x (a field on its own!)low-x (a field on its own!) bb

RHICbb

LHC

ccRHIC

ccLHC

100

25

accessible x1, x2 regions in the ALICE experimentaccessible x1, x2 regions in the ALICE experiment

central detector

muonarm


6565

Heavy Flavour Quenching?Heavy Flavour Quenching? some prediction ...some prediction ...

TBD

pp

TBD

AA

collT

BDAA dpdN

dpdNN

pR//1)( ,

,,

[Armesto et al.: Phys.Rev. D71 (2005) 054027]

charm beauty


6666

DD00 K K--++

expected ALICE expected ALICE performance performance S/B ≈ 10 %S/B ≈ 10 % S/S/(S+B) ≈ 40 (S+B) ≈ 40

(1 month Pb-Pb running)(1 month Pb-Pb running)

statistical.

systematic.

ppTT - differential - differential similar performance in ppsimilar performance in pp

(wider primary vertex (wider primary vertex spread)spread)FA - Quark Matter Italia - Roma Sanità - 24 aprile

2009

6767

Beauty to electronsBeauty to electrons Expected ALICE performance (1 month Pb-Pb)Expected ALICE performance (1 month Pb-Pb)

ee±± identification from TRD and dE/dx in TPC identification from TRD and dE/dx in TPC impact parameter from ITSimpact parameter from ITS

pt > 2 GeV/c , 200 < |d0| < 600 m 80% purity8 104 e from B

pt > 2 GeV/c , 200 < |d0| < 600 m 80% purity8 104 e from B

S/(S+B)S/(S+B) S per 10S per 1077 central Pb-Pb events central Pb-Pb events


6868

Electrons (from b) pElectrons (from b) ptt spectrum spectrum

Error compositionstat error

stat syst error

11% from overall normalization not included


6969

Beauty to single muonsBeauty to single muons expected in the muon armexpected in the muon arm

very high statistics and heavy flavour purity expectedvery high statistics and heavy flavour purity expectedFA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

7070

Beauty to dimuonsBeauty to dimuons Two main sources:Two main sources:

B µ+ + D + Xµ- + X

B B µ- + XX + µ+

“BDSAME” “BBDIFF”


Beauty to dimuonsBeauty to dimuons

7171

low mass

high mass

low mass: µ+ and µ- from decay of same B or B

high mass: µ+ and µ- from decay of B and B

Consistency Consistency check!check!


7272

tDpp

tDAA

collt

DAA dpdN

dpdNN

pR//1)(

tepp

teAA

collt

eAA dpdN

dpdNN

pR//1)(

Expected ALICE performance Expected ALICE performance on D, B R on D, B RAAAA

mb = 4.8 GeV

D0 K B e + X

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

mass dependencecolour charge dependence

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

hAAt

DAAthD pRpRpR


7373

Charm vCharm v22 at LHC? at LHC? Full reconstruction of D decays at LHC Full reconstruction of D decays at LHC

qualitatively different measurement from non-photonic electrons!qualitatively different measurement from non-photonic electrons! b vs cb vs c better correlation with original heavy-quark momentumbetter correlation with original heavy-quark momentum

First indications from preliminary studies in ALICE: First indications from preliminary studies in ALICE: expected error ~ few % (D vexpected error ~ few % (D v22))


7474

DDss++

DDss++

as probe of hadronization?as probe of hadronization? from string fragmentation: cs / cd ~ 1/3from string fragmentation: cs / cd ~ 1/3

after decays: Dafter decays: Dss++ (cs) / D (cs) / D++ (cd) ~ 0.6 (cd) ~ 0.6

from recombination: cs / cd ~ N(s) / N(d)from recombination: cs / cd ~ N(s) / N(d) how large at LHC?how large at LHC?

experimentally accessible?experimentally accessible? DD++ (c (c ~ 310 µm) ~ 310 µm) K K--++++ with BR ~ 9.2 % with BR ~ 9.2 %

in Alice: similar performance as for Din Alice: similar performance as for D00 K K--++

DDss++ (c (c ~ 150 µm) ~ 150 µm) K K--KK++++ with BR ~ 4.4 % with BR ~ 4.4 %

but mostly resonant decays: but mostly resonant decays: ++ or K or K00**KK++ (non resonant only 20 %) (non resonant only 20 %)

favours bkgnd rejection (for Dfavours bkgnd rejection (for D++ K K--++++, non-resonant ~ 96 %), non-resonant ~ 96 %) may be well visible (expecially if Dmay be well visible (expecially if Dss

++/D/D++ is large!) is large!)

DDss v v22 would be particularly interesting! would be particularly interesting!FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

7575

At LHC: At LHC: realreal jets! jets!

2 GeV 20 GeV 100 GeV 200 GeV

Mini-Jets 100/event 1/event 100k/month Well visible event-by-event! e.g. 100 GeV jet + underlying event:Well visible event-by-event! e.g. 100 GeV jet + underlying event:

e.g.: study quenching with b-tagged jets!e.g.: study quenching with b-tagged jets!

7676

b taggingb tagging ATLAS u rejection (RATLAS u rejection (Ruu) performance in Pb-Pb) performance in Pb-Pb

H H bb, uu with M bb, uu with MHH = 400 GeV = 400 GeV


7777

Away side cone?Away side cone? Collective behaviour Collective behaviour

opposite to jet?opposite to jet? eg: Mach cone eg: Mach cone

[Casalderrey-Solana, et al.: hep-ph/0411315][Casalderrey-Solana, et al.: hep-ph/0411315][Stocker: Nucl.Phys. A750 (2005) 121])[Stocker: Nucl.Phys. A750 (2005) 121])

Assume effect is real:Assume effect is real: What happens with big-fat-heavy quark jets?What happens with big-fat-heavy quark jets?

PHENIX Preliminary

*=

*=

John Lajoie @ QM2006


7878

Modified Mach cone?Modified Mach cone? Heavy quarks at moderate pHeavy quarks at moderate pTT move with substantially lower move with substantially lower

speedspeed e.g.: for beauty, taking:e.g.: for beauty, taking:

ccSS22 = 0.2 = 0.2

m(b) = 4.5 GeVm(b) = 4.5 GeV b quark is “subsonic” b quark is “subsonic”

for pfor p < 2.25 GeV< 2.25 GeV for p ~ 3-4 GeV, for p ~ 3-4 GeV,

shock wave angle ~ 40shock wave angle ~ 40OO

[FA, E Shuryak: J.Phys. G31 (2005) 19][FA, E Shuryak: J.Phys. G31 (2005) 19]

p(b) [GeV]

shoc

k w

ave

angl

e [d

egre

es]

Now: Now: observing THAT observing THAT

would be something!would be something!



7979

ConclusioniConclusioni Con gli heavy flavour, la Natura ci mette gentilmente a Con gli heavy flavour, la Natura ci mette gentilmente a

disposizione un meraviglioso strumento per studiare le proprietà disposizione un meraviglioso strumento per studiare le proprietà del mezzo prodotto nelle collisioni nucleari ultrarelativistichedel mezzo prodotto nelle collisioni nucleari ultrarelativistiche

LHC è una macchina da heavy flavour LHC è una macchina da heavy flavour alte rese di produzione moltoalte rese di produzione molto gamma in pgamma in pTT estesa estesa jet ben sviluppatijet ben sviluppati

L’esperimento ALICE è ben attrezzato per questa fisicL’esperimento ALICE è ben attrezzato per questa fisicaa

introduzione alla fisica degli heavy flavour nelle collisioni nucleari ultrarelativistiche

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