Stato della ricerca e prospettive in collisioni ultrarelativistiche nucleo-nucleo

11

Stato della ricerca e prospettive Stato della ricerca e prospettive in collisioni ultrarelativistiche in collisioni ultrarelativistiche

nucleo-nucleonucleo-nucleoFederico AntinoriFederico Antinori

INFN PadovaINFN Padova

FA - IFAE 2006 - Pavia, 20 aprile 2006FA - IFAE 2006 - Pavia, 20 aprile 2006 22

ContenutoContenuto

Introduzione (QGP, SPS)Introduzione (QGP, SPS)

Risultati principali di RHICRisultati principali di RHIC

Prospettiva: “hard probes” (heavy flavour)Prospettiva: “hard probes” (heavy flavour)

non tratterò di FAIR (GSI, “bassa” energia)non tratterò di FAIR (GSI, “bassa” energia)


QCD phase diagramQCD phase diagram

Tc ~ 170 MeV

~ 5 - 10 nuclear

Quark-Gluon Plasma

Hadron gas

Nuclearmatter

Neutron Star

SPSAGS

Early Universe LHCRHIC

Baryon density

Tem

pera

ture

c ~ 1 GeV/fm3

~ 10 s after Big Bang


(Partial) Chiral Symmetry Restoration(Partial) Chiral Symmetry Restoration Confined quarks acquire an additional mass (~ 350 MeV) Confined quarks acquire an additional mass (~ 350 MeV)

dynamically, through the confining effect of strong interactionsdynamically, through the confining effect of strong interactions M(proton) M(proton) 938 MeV; m(u)+m(u)+m(d) = 10 938 MeV; m(u)+m(u)+m(d) = 1015 MeV15 MeV

Deconfinement is expected to be accompanied by a restoration Deconfinement is expected to be accompanied by a restoration of the masses to the “bare” values they have in the Lagrangeanof the masses to the “bare” values they have in the Lagrangean

As quarks become deconfined, the masses would go back to the As quarks become deconfined, the masses would go back to the bare values; e.g.: bare values; e.g.: m(u,d): ~ 350 MeV m(u,d): ~ 350 MeV a few MeV a few MeV m(s): ~ 500 MeV m(s): ~ 500 MeV ~ 150 MeV ~ 150 MeV

55

Due predizioni storiche...Due predizioni storiche...


Strangeness enhancementStrangeness enhancement restoration of restoration of symmetry -> increased production of ssymmetry -> increased production of s

mass of strange quark in QGP expected to go back to current mass of strange quark in QGP expected to go back to current valuevalue mmSS ~ 150 MeV ~ Tc ~ 150 MeV ~ Tc

copious production of ss pairs, mostly by gg fusion copious production of ss pairs, mostly by gg fusion [[Rafelski: Phys. Rep. 88 (1982) 331]Rafelski: Phys. Rep. 88 (1982) 331][Rafelski-Müller: P. R. Lett. 48 (1982) 1066[Rafelski-Müller: P. R. Lett. 48 (1982) 1066]]

deconfinement deconfinement stronger effect stronger effect for multi-strangefor multi-strange can be built recombining uncorrelated can be built recombining uncorrelated

s quarks produced in independent s quarks produced in independent microscopic reactions microscopic reactions

strangeness enhancement increasing strangeness enhancement increasing with strangeness contentwith strangeness content

[Koch, Müller & Rafelski: Phys. Rep. 142 (1986) 167][Koch, Müller & Rafelski: Phys. Rep. 142 (1986) 167]

s

u

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sd d

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+

+

-

p

-


QGP signature proposed by Matsui and Satz, 1986QGP signature proposed by Matsui and Satz, 1986

In the plasma phase the interaction potential is expected to be In the plasma phase the interaction potential is expected to be screened beyond the Debye length screened beyond the Debye length D D (analogous to e.m. Debye (analogous to e.m. Debye screening)screening)

Charmonium (cc) and bottonium (bb) states with r > Charmonium (cc) and bottonium (bb) states with r > D D will not will not bind; their production will be suppressedbind; their production will be suppressed

Charmonium suppressionCharmonium suppression

For T ~ 200 MeV:For T ~ 200 MeV:DD ~ 0.1 – 0.2 fm ~ 0.1 – 0.2 fm216

1~TD

(very) rough estimate...(very) rough estimate...

88

L’era dell’SPS...L’era dell’SPS...


CERN heavy-ion programmeCERN heavy-ion programme 1994 to 20031994 to 2003 typically 4 - 6 weeks per year Pb nuclei @ 158 A GeV/ctypically 4 - 6 weeks per year Pb nuclei @ 158 A GeV/c

(40 GeV in 1999, 158 GeV In in 2003, + short 20, 30, 80 GeV runs)(40 GeV in 1999, 158 GeV In in 2003, + short 20, 30, 80 GeV runs) 9 experiments:9 experiments:

WA97WA97 ((silicon pixel telescope spectrometersilicon pixel telescope spectrometer: production of strange and : production of strange and multiply strange particles)multiply strange particles)

WA98WA98 ( (photon and hadron spectrometerphoton and hadron spectrometer: photon and hadron production): photon and hadron production) NA44 NA44 ((single arm spectrometersingle arm spectrometer: particle spectra, interferometry, particle : particle spectra, interferometry, particle

correlations)correlations) NA45NA45 ( (ee++ee-- spectrometer spectrometer: low mass lepton pairs): low mass lepton pairs) NA49NA49 ( (large acceptance TPClarge acceptance TPC: particle spectra, strangeness production, : particle spectra, strangeness production,

interferometry, event-by-event studies…)interferometry, event-by-event studies…) NA50NA50 ( (dimuon spectrometerdimuon spectrometer: high mass lepton pairs, J/: high mass lepton pairs, J/ production) production) NA52NA52 ((focussing spectrometerfocussing spectrometer: strangelet search, particle production): strangelet search, particle production) NA57NA57 ( (silicon pixel telescope spectrometersilicon pixel telescope spectrometer: production of strange and : production of strange and

multiply strange particles)multiply strange particles) NA60NA60 ( (dimuon spectrometer + pixelsdimuon spectrometer + pixels: dileptons and charm): dileptons and charm)


A Pb-Pb collision at the SPSA Pb-Pb collision at the SPS ““Busy” events! Busy” events!

(thousands of (thousands of produced particles)produced particles)

High granularity High granularity detectors are detectors are employed (TPC, Si employed (TPC, Si Pixels,...)Pixels,...)


Particle productionParticle production

Rapidity distribution for Rapidity distribution for negative hadrons negative hadrons (mostly pions) for (mostly pions) for central Pb-Pb collisions central Pb-Pb collisions (from NA49)(from NA49)

~ 2500 hadrons per ~ 2500 hadrons per collisioncollision

corresponding to an corresponding to an initial energy density of initial energy density of 2 – 3 GeV/fm3 2 – 3 GeV/fm3


Strangeness enhancement at the Strangeness enhancement at the SPSSPS

Enhancement relative to p-BeEnhancement relative to p-BeEnhancement is larger for particles of higher strangeness content (QGP prediction!) up to a factor ~ 20 for

So far, no hadronic model has reproduced these observations (try harder!)

Actually, the most reliable hadronic models predicted an opposite behaviour of enhancement vs strangeness


J/J/ suppression at the SPS suppression at the SPS measured/expected measured/expected

J/J/suppression vs estimated suppression vs estimated energy densityenergy density anomalous suppression sets anomalous suppression sets

in at in at ~ 2.3 GeV/fm ~ 2.3 GeV/fm33 ( (bb ~ 8 ~ 8 fm)fm)

effect seems to accelerate at effect seems to accelerate at ~ 3 GeV/fm ~ 3 GeV/fm33 ( (bb ~ 3.6 fm) ~ 3.6 fm)

this pattern has been this pattern has been interpreted as successive interpreted as successive melting of the melting of the c c and of the and of the J/J/


What have we learned at the SPS?What have we learned at the SPS? We create a strongly interacting fireball in a state of very large energy We create a strongly interacting fireball in a state of very large energy

density, at which the very concept of individual, separated hadrons is not too density, at which the very concept of individual, separated hadrons is not too meaningfulmeaningful

At freeze-out (when the reinteractions between the produced particles cease) At freeze-out (when the reinteractions between the produced particles cease) the system is expanding at ~ ½ cthe system is expanding at ~ ½ c

The properties of this state are not explained in terms of those of a The properties of this state are not explained in terms of those of a conventional system of strongly interacting hadrons: we have found a new conventional system of strongly interacting hadrons: we have found a new “regime” for strongly interacting system, which has to be investigated further“regime” for strongly interacting system, which has to be investigated further

This state exhibits many features of the QGP, in particular the expected This state exhibits many features of the QGP, in particular the expected effects of deconfinement (J/effects of deconfinement (J/ suppression) and chiral simmetry restoration suppression) and chiral simmetry restoration (strangeness enhancement) are there. It looks like the partonic degrees of (strangeness enhancement) are there. It looks like the partonic degrees of freedom are activefreedom are active

in order to better understand the properties of this state we need to go to in order to better understand the properties of this state we need to go to higher energy higher energy RHIC, LHC RHIC, LHC conditions closer to ideal, harder probesconditions closer to ideal, harder probes


The next step: RHICThe next step: RHIC Relativistic Heavy Ion Collider (RHIC) Relativistic Heavy Ion Collider (RHIC)

at Brookhaven National Lab (USA - NY)at Brookhaven National Lab (USA - NY)

Au-Au collision in STARAu-Au collision in STAR

ssNNNN = 200 GeV, = 200 GeV, 10 from SPS: 10 from SPS: higher energy densities, temperatures, expected QGP lifetimes, higher energy densities, temperatures, expected QGP lifetimes,

volumesvolumes QCD calculations more reliable QCD calculations more reliable improve our understanding! improve our understanding! 10 units rapidity span: better separation of central and 10 units rapidity span: better separation of central and

fragmentation regionsfragmentation regions

4 dedicated, complementary experiments: 4 dedicated, complementary experiments: 2 larger (2 larger (STARSTAR: hadronic signals, : hadronic signals, PHENIXPHENIX: leptonic, e.m. signals),: leptonic, e.m. signals), 2 smaller (2 smaller (PHOBOSPHOBOS, , BRAHMSBRAHMS) )


RHIC HeadlinesRHIC Headlines Rather low multiplicityRather low multiplicity

Gluon saturation? (“Colour Glass”)Gluon saturation? (“Colour Glass”)

Large Elliptic Flow Large Elliptic Flow v2v2

High pHigh pTT Suppression Suppression RRcpcp, R, RAAAA

Suppression of Away-Side JetsSuppression of Away-Side Jets Plus an New Structure in Away-Side?Plus an New Structure in Away-Side?

Valence Quark Counting RulesValence Quark Counting Rules Recombination?Recombination?


Particle multiplicityParticle multiplicity

Multiplicity per nucleon-nucleon collision increases Bjorken estimate of energy density: 5.5 GeV/fm3 Extrapolation to LHC: dNch/dy ~ 2500


Colour Glass?Colour Glass? At small x, large A, saturation of gluon pdf’s?At small x, large A, saturation of gluon pdf’s?

would explain relatively would explain relatively low multiplicitylow multiplicity

1919

Elliptic FlowElliptic Flow Non-central collisions are azimuthally asymmetricNon-central collisions are azimuthally asymmetric

The transfer of this asymmetry to momentum space provides a The transfer of this asymmetry to momentum space provides a measure of the strength of collective phenomena measure of the strength of collective phenomena

Large mean free path Large mean free path particles stream out isotropically, no memory of the asymmetry particles stream out isotropically, no memory of the asymmetry extreme: ideal gas (infinite mean free path) extreme: ideal gas (infinite mean free path)

Small mean free pathSmall mean free path larger density gradient -> larger pressure gradient -> larger larger density gradient -> larger pressure gradient -> larger

momentum momentum extreme: ideal liquid (zero mean free path, hydrodynamic limit)extreme: ideal liquid (zero mean free path, hydrodynamic limit)

Reactionplane

In-planeOut

-of-p

lane

Y

XFlow

Flow

Reactionplane

In-planeOut

-of-p

lane

Y

XFlow

Flow

Reactionplane

In-planeOut

-of-p

lane

Y

XFlow

Flow


Azimuthal AsymmetryAzimuthal Asymmetry

at low pat low pTT: azimuthal : azimuthal asymmetry as large as asymmetry as large as expected at hydro limitexpected at hydro limit

very far from “ideal very far from “ideal gas” picture of plasmagas” picture of plasma

...)2cos(2)cos(2121

21

vvdydpp

dNdyddpp

dN

TTTT

flow" directed" cos1 v flow" elliptic" 2cos2 v


RRcpcp, R, RAAAA, R, RdAudAu

AApp

AAAA

1YieldYield

NbinR

dAupp

dAudAu

1YieldYield

NbinR

central AA,

periphAA,

periph AA,

central AA,cp Yield

YieldNbin

NbinR

Yield/collision in central collisionsYield/collision in central collisionsYield/collision in peripheral collisionsYield/collision in peripheral collisions

Yield/collision in nucleus-nucleusYield/collision in nucleus-nucleus Yield/collision in proton-protonYield/collision in proton-proton

Yield/collision in deuteron-nucleusYield/collision in deuteron-nucleus Yield/collision in proton-protonYield/collision in proton-proton


High pHigh pTT suppression suppression

High pHigh pTT particle particle production expected to production expected to scale with number of scale with number of binary NN collisions if no binary NN collisions if no medium effectsmedium effects

Clearly does not work for Clearly does not work for more central collisionsmore central collisions


AA vs ppAA vs pp Differences can arise due to both initial-state and final-state Differences can arise due to both initial-state and final-state

effectseffects

[David d’Enterria]

2424

Centrality DependenceCentrality Dependence

Opposite behaviour with centralityOpposite behaviour with centrality Looks like suppression in AA is due to mediumLooks like suppression in AA is due to medium Parton energy-loss in the medium? (“Jet Quenching”)Parton energy-loss in the medium? (“Jet Quenching”)

Preliminary DataFinal Data

Au-AuAu-Au(“cold” matter and medium effects)(“cold” matter and medium effects)

dAudAu(only “cold” matter effects expected)(only “cold” matter effects expected)


Azimuthal Correlations (pp)Azimuthal Correlations (pp) In high energy collisions In high energy collisions

particles are correlated in particles are correlated in azimuth due to jetsazimuth due to jets

e.g.: at RHIC in proton-e.g.: at RHIC in proton-proton collisions from STARproton collisions from STAR ““trigger” particle: trigger” particle:

4 < p 4 < pTT< 6 GeV/c< 6 GeV/c associated particles: associated particles:

ppTT > 2 GeV/c > 2 GeV/c

trigger

Adler et al., PRL90:082302 (2003), STAR

near-side

away-side


Azimuthal CorrelationsAzimuthal Correlations away-side jet still present in dAuaway-side jet still present in dAu

but disappears in central AuAubut disappears in central AuAu

away-side jet quenched?away-side jet quenched?

trigger bias on jets produced trigger bias on jets produced close to surface?close to surface?

Adams et al., Phys. Rev. Let. 91 (2003)

qq

hadronsleadingparticle

is this what happens?


Two peaks?Two peaks? Disappearance of away jet in Disappearance of away jet in

central collisions at RHICcentral collisions at RHIC 4 < p4 < pTT(trig) < 6 GeV/c(trig) < 6 GeV/c ppTT(assoc) > 2 GeV/c(assoc) > 2 GeV/c

if pif pTT(assoc) is lowered, peak turns (assoc) is lowered, peak turns up again, but up again, but with strange shapewith strange shape:: 0.15 < p0.15 < pTT(assoc) < 4 GeV/c(assoc) < 4 GeV/c

(1/N

trig)

dN/d

()

STAR Preliminary

p+p Au+Au 5%trig4 6 GeV/c

0.15 4 GeV/cT

T

pp

Fit to near side: const. + gaussian + Borghini-cos(fixed)

stat. mom. conserv.Borghini et al.

free fit


[F. Wang: QM 2004][F. Wang: QM 2004]


Similar results from PHENIX, tooSimilar results from PHENIX, too

(1/N

trig)

dN

/d()

STAR Preliminary


0.15 4 GeV/cT

T

pp



free fit


(1/N

trig)

dN

/d()

STAR Preliminary


0.15 4 GeV/cT

T

pp

(1/N

trig)

dN

/d()

STAR Preliminary


0.15 4 GeV/cT

T

pp



free fit




free fit


Low pLow pTT associated associated particles seem to peak particles seem to peak ~ 1 radian (~ 60~ 1 radian (~ 60OO))away from away from

PHENIXPHENIX STARSTAR


Shock wave?Shock wave? Idea:Idea:[Casalderrey-Solana, Shuryak, Teaney: [Casalderrey-Solana, Shuryak, Teaney:

hep-ph/0411315]hep-ph/0411315](see also [Stocker: Nucl.Phys. A750 (2005) 121])(see also [Stocker: Nucl.Phys. A750 (2005) 121])

medium is densemedium is dense ““away jet” parton travels through away jet” parton travels through

medium with speed ~ cmedium with speed ~ c faster than speed of sound in faster than speed of sound in

medium: cmedium: css shock wave (“sonic boom”) is shock wave (“sonic boom”) is

emitted at angle:emitted at angle:

with cwith css22 ~ 0.2 : ~ 0.2 :

ccsarccos

)60( 1


Baryon puzzle @ RHICBaryon puzzle @ RHIC Central Au-Au: as many Central Au-Au: as many --

(K(K--) as p () as p () at p) at pTT ~ 1.5 ~ 1.5 2.5 2.5 GeV GeV

ee++ee-- jet (SLD) jet (SLD) very few baryons very few baryons

from from fragmentation!fragmentation!

K

p

H.Huang @ SQM 2004


if loss is partonic, shouldn’t it if loss is partonic, shouldn’t it affect p and affect p and in the same way? in the same way?

RcpRcp

central AA,

periphAA,

periph AA,

central AA,cp Yield

YieldNcoll

NcollR

strange particles come to strange particles come to rescue!rescue!


Quark RecombinationQuark Recombination if hadrons are formed by recombination, if hadrons are formed by recombination, features of the parton features of the parton

spectrum are shifted to higher pspectrum are shifted to higher pTT in the hadron spectrum, in the hadron spectrum, in a different way for mesons and baryons in a different way for mesons and baryons constituent quark countingconstituent quark counting

s

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sd d

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S.Bass @ SQM`04


Where should recombination Where should recombination work?work?

Proponents say @ pProponents say @ pTT between 1 and 4 GeV (6 GeV) for mesons between 1 and 4 GeV (6 GeV) for mesons (baryons)(baryons) hydro below, fragmentation above (at RHIC energy)hydro below, fragmentation above (at RHIC energy)

recombining partons:p1+p2=ph

fragmenting parton:ph = z p, z<1

R.Fries @ QM`04


elliptic flow velliptic flow v22

Recombination also offers an explanation for the vRecombination also offers an explanation for the v22 baryon baryon puzzle...puzzle...

STAR Preliminary

scaled with n(quarks)

...)2cos(2)cos(2121

21

vvdydpp

dNdyddpp

dN

TTTT

flow"direct " cos1 v flow" elliptic" 2cos2 v


A few hiccups...A few hiccups...

Strict recombination has a few theoretical problems...Strict recombination has a few theoretical problems... it violates 2it violates 2ndnd law of thermodynamics law of thermodynamics

reduction of the number of particles reduction of the number of particles lower disorder lower disorder entropy decreased entropy decreased

it actually also violates the 1it actually also violates the 1stst...... impossible to conserve energy and momentum simultaneouslyimpossible to conserve energy and momentum simultaneously

what happens to gluons?what happens to gluons?


Picture emerging from RHICPicture emerging from RHIC System formed in AuAu collisionsSystem formed in AuAu collisions

presumably partonicpresumably partonic Strongly collective (~ liquid behaviour)Strongly collective (~ liquid behaviour) Very opaque medium (strong energy loss)Very opaque medium (strong energy loss) Indications for hadronization by recombinationIndications for hadronization by recombination

How can we test this scenario?How can we test this scenario? Need to confirm this picture with a different probeNeed to confirm this picture with a different probe Heavy quarksHeavy quarks


Charm & beauty: ideal probesCharm & beauty: ideal probes calculable in pQCD; calibration measurement from ppcalculable in pQCD; calibration measurement from pp

rather solid groundrather solid ground caveat: modification of initial state effects from pp to AAcaveat: modification of initial state effects from pp to AA

shadowing ~ 30 %shadowing ~ 30 % saturation?saturation?

pA reference fundamentalpA reference fundamental!!

produced essentially in initial impactproduced essentially in initial impact probes of high density phaseprobes of high density phase

no extra production at hadronizationno extra production at hadronization probes of fragmentation probes of fragmentation

e.g.: independent string fragmentation vs recombinatione.g.: independent string fragmentation vs recombination


Probing the mediumProbing the medium quenching vs colour chargequenching vs colour charge

heavy flavour from quark (Cheavy flavour from quark (CRR = 4/3) jets = 4/3) jets light flavour from (plight flavour from (pTT-dep) mix of quark and gluon (C-dep) mix of quark and gluon (CRR = 3) jets = 3) jets

quenching vs massquenching vs mass heavy flavour predicted to suffer less energy lossheavy flavour predicted to suffer less energy loss

gluonstrahlung: dead-cone effectgluonstrahlung: dead-cone effect beauty vs charmbeauty vs charm

heavy flavour should provide a fundamental cross-heavy flavour should provide a fundamental cross-check of quenching picture emerging from RHICcheck of quenching picture emerging from RHIC

at LHC: high stats and fully developed jetsat LHC: high stats and fully developed jets


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


Heavy flavour energy loss?Heavy flavour energy loss?

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 predominantly from gluon jets, light hadrons originate predominantly from gluon jets, heavy flavoured hadrons originate from heavy quark jets heavy flavoured hadrons originate from heavy 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”)


Large suppression at RHIC!Large suppression at RHIC! yet, region above 3-4 GeV yet, region above 3-4 GeV

expected to be dominated expected to be dominated by beauty...by beauty...

[Xin Dong@QM05]

n.p. electrons ~ as suppressed as n.p. electrons ~ as suppressed as expected for c only (no b)expected for c only (no b)

scaled to

M. Cacciari et al., hep-ph/0502203

[J.Bielcik @QM05] disentangling c/b is a mustdisentangling c/b is a must!! e.g. full reconstruction of D verticese.g. full reconstruction of D vertices


||<0.9:B = 0.4 TTOFTPCITS with: - Si pixels- Si drifts- Si strips

PIXEL CELL

z: 425 m

r: 50 m

Two layers:r = 4 cmr = 7 cm

9.8 M

ALICEALICE


Track Impact ParameterTrack Impact Parameter

expected dexpected d00 resolution resolution (() )


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% cent)Pb-Pb 5.5 TeV (5% cent)0.160.16 // 0.0070.00711 // 1111.211.2 // 0.50.5 pp 14 TeVpp 14 TeV

shadowingshadowingsystemsystem NN x-sect (mb)NN x-sect (mb) total multiplicitytotal multiplicity

PbPbpp

PbPbpp

cc bbPbPb/pp PbPb/pp


some prediction ...some prediction ...T

BDpp

TBD

AA

collT

BDAA dpdN

dpdNN

pR//1)( ,

,,

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

charm beauty


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 spread)(wider primary vertex spread)


RRAAAA(D) in ALICE(D) in ALICE

Low pT (< 6–7 GeV/c)Nuclear shadowing ‘High’ pT (6–15 GeV/c)

expected performance (1 month Pb-Pb, 9 months expected performance (1 month Pb-Pb, 9 months p-p)p-p)


B B e e±± + X + X 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


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!


b taggingb tagging e.g.: ATLAS u rejection (Re.g.: ATLAS 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


Away side?Away side? Collective behaviour opposite to Collective behaviour opposite to

jetjet 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])

What happens with big-fat-heavy-quark jets?What happens with big-fat-heavy-quark jets? e.g.: modification of Mach cone? e.g.: modification of Mach cone? [FA, E Shuryak: J.Phys. G31 (2005) 19][FA, E Shuryak: J.Phys. G31 (2005) 19]


Machine commissioning scenarioMachine commissioning scenario (as envisaged today)(as envisaged today)

T0T0 (= 1st of July 2007 as of today) (= 1st of July 2007 as of today) One monthOne month to get the machine ready for beams ( to get the machine ready for beams (T0 + 1 monthT0 + 1 month)) Three monthsThree months to commission the machine with beams ( to commission the machine with beams (T0 + 4 T0 + 4

monthsmonths)) One monthOne month of rather stable operations, interleaved with machine of rather stable operations, interleaved with machine

development with 43 and 156 bunches, with the possibility of development with 43 and 156 bunches, with the possibility of collisions for physics during nights (~ 20 shifts of 10 hours each L ~ collisions for physics during nights (~ 20 shifts of 10 hours each L ~ 1to 3.5x101to 3.5x103030cmcm–2–2ss–1–1) () (T0 + 5 monthsT0 + 5 months))

Shutdown (Shutdown (T0 + 8 to 9 monthsT0 + 8 to 9 months): today machine people talk about 3 ): today machine people talk about 3 to 4 months. It will depend on requirements by experiments. to 4 months. It will depend on requirements by experiments. If T0 = 1st of July, start of shutdown will coincide with the Christmas If T0 = 1st of July, start of shutdown will coincide with the Christmas holidays!holidays!

July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar

Shutdown 3 to 4 months?Stable beamsPreparation

“first minutes” of data

…First collisions…….

T0 first large data sample

first Pb-Pb collisions in 2008


Example: B in ppExample: B in pp B B e + X e + X

electron id in TRD and TPC, electron impact parameter from ITSelectron id in TRD and TPC, electron impact parameter from ITS

Expected stats from “first large pp sample” in ALICE ~ a few 10Expected stats from “first large pp sample” in ALICE ~ a few 1077 evts evtsCarlo Bombonati


ConclusioniConclusioni StatoStato: il campo è più vivo che mai: il campo è più vivo che mai

SPS: osservazione delle “signatures” storicheSPS: osservazione delle “signatures” storiche RHIC: comportamento idrodinamico? forte attenuazione dei RHIC: comportamento idrodinamico? forte attenuazione dei

jet?jet?

ProspettiveProspettive: l’LHC è una macchina ideale per AA: l’LHC è una macchina ideale per AA altissima energia -> “deep deconfinement”altissima energia -> “deep deconfinement” alte rate di hard probesalte rate di hard probes un esperimento dedicato (ALICE), buone performance in altri un esperimento dedicato (ALICE), buone performance in altri

due (ATLAS, CMS)due (ATLAS, CMS)



Lattice QCDLattice QCD

zero baryon density, 3 zero baryon density, 3 flavoursflavours

changes rapidly around changes rapidly around TTcc

TTcc = 170 MeV: = 170 MeV: cc = 0.6 GeV/fm = 0.6 GeV/fm33

at at TT~1.2 ~1.2 TTcc settles at settles at about 80% of the Stefan-about 80% of the Stefan-Boltzmann value for an Boltzmann value for an ideal gas of q,q g (ideal gas of q,q g (SBSB))

3 flavours; (q-q)=0

In lattice QCD, non-perturbative problems are treated by discretization on a space-time lattice

Documents

Stato della ricerca e prospettive in collisioni ultrarelativistiche nucleo-nucleo