From Heavy Ions to Quark Matter Episode 1 Federico Antinori (INFN Padova, Italy & CERN, Geneva,...

From Heavy Ions From Heavy Ions to Quark Matterto Quark Matter

Episode 1Episode 1Federico AntinoriFederico Antinori

(INFN Padova, Italy & CERN, Geneva, Switzerland)(INFN Padova, Italy & CERN, Geneva, Switzerland)11

8 November 2010: the beginning of a new era for Heavy Ion 8 November 2010: the beginning of a new era for Heavy Ion PhysicsPhysics

A-A collisions in the LHC!A-A collisions in the LHC!

22FA - XVI Frascati Spring School - 7 to 11 May 2012

Two puzzles in QCDTwo puzzles in QCD

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The Standard Model and QCDThe Standard Model and QCD

strong interaction:strong interaction: binds quarks into hadronsbinds quarks into hadrons binds nucleons into nucleibinds nucleons into nuclei

described by QCD: described by QCD: interaction between particles interaction between particles

carrying colour charge (quarks, carrying colour charge (quarks, gluons)gluons)

mediated by strong force carriers mediated by strong force carriers (gluons)(gluons)

very successful theoryvery successful theory

beauty


e.g.: pQCD vs production of high energy jetse.g.: pQCD vs production of high energy jets


The Standard Model and QCDThe Standard Model and QCD

strong interaction:strong interaction: binds quarks into hadronsbinds quarks into hadrons binds nucleons into nucleibinds nucleons into nuclei

described by QCD: described by QCD: interaction between particles interaction between particles

carrying colour charge (quarks, carrying colour charge (quarks, gluons)gluons)

mediated by strong force carriers mediated by strong force carriers (gluons)(gluons)

very successful theoryvery successful theory jet productionjet production particle production at high pparticle production at high pTT

heavy flavour productionheavy flavour production ……

… … but with outstanding puzzlesbut with outstanding puzzles

beauty


Two puzzles in QCD: i) hadron Two puzzles in QCD: i) hadron massesmasses

A proton is thought to be made of A proton is thought to be made of two u and one d quarkstwo u and one d quarks

The sum of their masses is The sum of their masses is around 12 MeVaround 12 MeV

... but the proton mass is 938 ... but the proton mass is 938 MeV!MeV!

how is the extra mass how is the extra mass generated?generated?

beauty


Two puzzles in QCD: ii) Two puzzles in QCD: ii) confinementconfinement

Nobody ever succeeded in Nobody ever succeeded in detecting an isolated quarkdetecting an isolated quark

Quarks seem to be Quarks seem to be permanently confined within permanently confined within protons, neutrons, pions and protons, neutrons, pions and other hadrons. other hadrons.

It looks like one half of the It looks like one half of the fundamental fermions are fundamental fermions are not directly observable… not directly observable…

why?why?

beauty


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

rigorous way of doing calculations in non-perturbative regime of QCD

discretization on a space-time lattice ultraviolet (large momentum scale) divergencies can be

avoided


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

per

atu

re

c ~ 1 GeV/fm3

~ 10 s after Big Bang

an “artist’s view”…an “artist’s view”…


Restoration of bare massesRestoration of bare masses

Confined quarks acquire an additional mass (~ 350 MeV) Confined quarks acquire an additional mass (~ 350 MeV) dynamically, through the confining effect of strong interactions dynamically, 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 Lagrangianof the masses to the “bare” values they have in the Lagrangian

As quarks become deconfined, the masses go back to the bare As quarks become deconfined, the masses go back to the bare values; e.g.: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

(This effect is usually referred to as “(This effect is usually referred to as “Partial Restoration of Chiral Partial Restoration of Chiral SymmetrySymmetry”. Chiral Symmetry: fermions and antifermions have opposite ”. Chiral Symmetry: fermions and antifermions have opposite helicity. The symmetry is exact only for massless particles, therefore its helicity. The symmetry is exact only for massless particles, therefore its restoration here is only partial)restoration here is only partial)


Big Bang and deconfinementBig Bang and deconfinement

we think that in the first we think that in the first instants of life of the instants of life of the Universe, quarks and gluons Universe, quarks and gluons were not trapped inside were not trapped inside hadrons (protons, neutrons, hadrons (protons, neutrons, …)……)…

but could move freely in a but could move freely in a “deconfined” state: “deconfined” state:

the Quark-Gluon Plasmathe Quark-Gluon Plasma


10 µs: the birth of hadrons10 µs: the birth of hadrons

after about 10 µs fron the Big after about 10 µs fron the Big Bang, the Universe cools down Bang, the Universe cools down to less than 2 10to less than 2 101212 degrees degrees

at that point, the QCD phase at that point, the QCD phase transition takes place: quarks transition takes place: quarks and gluons are confined inside and gluons are confined inside hadronshadrons

the familiar particles, such as the familiar particles, such as pions, kaons, protons and pions, kaons, protons and neutrons appear on the stage of neutrons appear on the stage of the Universethe Universe


how does matter behave in such extreme conditons?how does matter behave in such extreme conditons?

what are the properties of the Quark-Gluon Plasma?what are the properties of the Quark-Gluon Plasma?

even with the most powerful telescopes, we cannot go back in even with the most powerful telescopes, we cannot go back in time to less than ~ 400,000 years after the Big Bangtime to less than ~ 400,000 years after the Big Bang

How can we know more?How can we know more?


can we reproduce such a state in can we reproduce such a state in the laboratory?the laboratory? ~ 2000 billion degrees?~ 2000 billion degrees?

Nucleus – Nucleus collisionsNucleus – Nucleus collisions

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Nucleus-nucleus collisionsNucleus-nucleus collisions

How do we test this theory in the How do we test this theory in the lab?lab?

How can we compress/heat matter How can we compress/heat matter to such cosmic energy densities? to such cosmic energy densities?

By colliding two heavy nuclei at By colliding two heavy nuclei at ultrarelativistic energies we ultrarelativistic energies we recreate, for a short time span recreate, for a short time span (about 10(about 10-23-23s, or a few fm/c) the s, or a few fm/c) the conditions for deconfinementconditions for deconfinement


as the system expands and as the system expands and cools down it will undergo a cools down it will undergo a phase transition from QGP to phase transition from QGP to hadrons again, like at the hadrons again, like at the beginning of the life of the beginning of the life of the Universe: we end up with Universe: we end up with confined matter againconfined matter again QGP lifetime ~ a few fm/cQGP lifetime ~ a few fm/c

The properties of the medium The properties of the medium must be inferred from the must be inferred from the properties of the hadronic properties of the hadronic final statefinal state


Collisions of Heavy Nuclei at SPS and RHICCollisions of Heavy Nuclei at SPS and RHIC

Super Proton Synchrotron (SPS) at CERN (Geneva):Super Proton Synchrotron (SPS) at CERN (Geneva): Pb-Pb fixed target, p = 158 A GeV Pb-Pb fixed target, p = 158 A GeV s sNNNN = 17.3 GeV = 17.3 GeV 1994 - 20031994 - 2003 9 experiments: 9 experiments:

WA97 (WA97 (silicon pixel telescope spectrometersilicon pixel telescope spectrometer: production of strange and multiply strange particles): production of strange and multiply strange particles) WA98 (WA98 (photon and hadron spectrometerphoton and hadron spectrometer: photon and hadronn production): photon and hadronn production) NA44 (NA44 (single arm spectrometersingle arm spectrometer: particle spectra, interferometry, particle correlations): particle spectra, interferometry, particle correlations) NA45 (NA45 (ee++ee-- spectrometer spectrometer: low mass lepton pairs): low mass lepton pairs) NA49 (NA49 (large acceptance TPClarge acceptance TPC: particle spectra, strangeness production, interferometry, event-by-event , …): particle spectra, strangeness production, interferometry, event-by-event , …) NA50 (NA50 (dimuon spectrometerdimuon spectrometer: high mass lepton pairs, J/: high mass lepton pairs, J/ production) production) NA52 (NA52 (focussing spectrometerfocussing spectrometer: strangelet search, particle production): strangelet search, particle production) NA57 (NA57 (silicon pixel telescope spectrometersilicon pixel telescope spectrometer: production of strange and multiply strange particles): production of strange and multiply strange particles) NA60 (NA60 (dimuon spectrometer + pixelsdimuon spectrometer + pixels: dileptons and charm): dileptons and charm)

Relativistic Heavy Ion Collider (RHIC) at BNL (Long Island)Relativistic Heavy Ion Collider (RHIC) at BNL (Long Island) Au-Au collider, Au-Au collider, s sNNNN = 200 GeV = 200 GeV 2000 - …2000 - … 4 experiments:4 experiments:

STAR (STAR (multi-purpose experimentmulti-purpose experiment: focus on hadrons): focus on hadrons) PHENIX (PHENIX (multi-purpose experimentmulti-purpose experiment: focus on leptons, photons): focus on leptons, photons) BRAHMS (BRAHMS (two-arm spectrometertwo-arm spectrometer: particle spectra, forward rapidity): particle spectra, forward rapidity) PHOBOS (PHOBOS (silicon arraysilicon array: particle spectra): particle spectra)


Nucleus-Nucleus collisions at the Nucleus-Nucleus collisions at the LHC!LHC!

SPS RHIC LHC

sNN [GeV] 17.3 200 5500

dNch/dy 450 800 1600

ε [GeV/fm3] 3 5.5 ~ 10

large large εε deeper in deconfinement region deeper in deconfinement region closer to “ideal” behaviour?closer to “ideal” behaviour?

large cross section for “hard probes” !large cross section for “hard probes” ! a new set of tools to probe the medium propertiesa new set of tools to probe the medium properties

e.g.:e.g.:

Pb Pb

bb

b

b1919FA - XVI Frascati Spring School - 7 to 11 May 2012

FA - XVI Frascati Spring School - 7 to 11 May 2012 2020

Heavy Ions at CERNHeavy Ions at CERN

Acceleration of Pb ions:Acceleration of Pb ions: ECR source: PbECR source: Pb27+27+ (80 (80 A)A)

RFQ: PbRFQ: Pb27+27+ to 250 A keV to 250 A keV

Linac3: PbLinac3: Pb27+27+ to 4.2 A MeV to 4.2 A MeV

Stripper: PbStripper: Pb53+53+

PS Booster: PbPS Booster: Pb53+53+ to 95 A MeV to 95 A MeV

PS: PbPS: Pb53+53+ to 4.25 A GeV to 4.25 A GeV

Stripper: PbStripper: Pb82+82+ (full ionisation) (full ionisation)

SPS: PbSPS: Pb82+82+ to 158 A GeV to 158 A GeV

LHC: PbLHC: Pb82+82+ to 2.76 A TeV) to 2.76 A TeV)

Pb nuclei in the LHCPb nuclei in the LHC For 2011 Pb-Pb run:For 2011 Pb-Pb run:

~ 1.1 10~ 1.1 1088 ions/bunch ions/bunch 358 bunches (200 ns basic spacing) 358 bunches (200 ns basic spacing) β* = 1 m β* = 1 m L ~ 5 10L ~ 5 102626 cm cm-2-2ss-1-1 ~ 4000 Hz interaction rate~ 4000 Hz interaction rate

a dedicated AA experiment: ALICEa dedicated AA experiment: ALICE

and AA capability in ATLAS and CMSand AA capability in ATLAS and CMS


LHC as a HI acceleratorLHC as a HI accelerator

Fully ionised Fully ionised 208208Pb nucleus accelerated in LHCPb nucleus accelerated in LHC

(configuration magnetically identical to that for pp), e.g.:(configuration magnetically identical to that for pp), e.g.:

the relevant figure is the relevant figure is s per nucleon-nucleon collision: s per nucleon-nucleon collision: ssNNNN

… … of course, real life is more complicated…of course, real life is more complicated… ion collimationion collimation sensitivity of LHC instrumentationsensitivity of LHC instrumentation injection chaininjection chain ……

TeV 574TeV 782 pPb pZp

TeV 5.539.02

ppppPb

NN ssA

Z

A

Es

PeV 15.1PbPb s


Luminosity limitationsLuminosity limitations

Bound-Free Pair Production (BFPP):Bound-Free Pair Production (BFPP):

with subsequent loss of the with subsequent loss of the 208208PbPb81+81+

creates a small beam of creates a small beam of 208208PbPb81+81+, with an intensity , with an intensity Luminosity Luminosity impinging on a superconducting dipole (that you don’t want to quench…)impinging on a superconducting dipole (that you don’t want to quench…) cross section cross section Z Z77 (!) ~ 280 b for PbPb at LHC (hadronic cross section ~ 8 b…) (!) ~ 280 b for PbPb at LHC (hadronic cross section ~ 8 b…)

Collimation lossesCollimation losses collimation for ions (which can break up into fragments) is harder than for protonscollimation for ions (which can break up into fragments) is harder than for protons limitation on the total intensitylimitation on the total intensity

luminosity limited to ~ 10luminosity limited to ~ 102727 cm cm-2-2ss-1-1

ePbPbPbPb 81208 82208 82208 82208


A Pb-Pb collision at the LHCA Pb-Pb collision at the LHC


Geometry of a Pb-Pb collisionGeometry of a Pb-Pb collision central collisionscentral collisions

small small impact parameter bimpact parameter b high number of high number of participantsparticipants high high

multiplicitymultiplicity

peripheral collisionsperipheral collisions large large impact parameter bimpact parameter b low number of low number of participantsparticipants low low

multiplicitymultiplicity

for example: sum of the amplitudes for example: sum of the amplitudes in the ALICE V0 scintillators in the ALICE V0 scintillators

reproduced by simple model (reproduced by simple model (redred):): random relative position of nuclei in random relative position of nuclei in

transverse planetransverse plane Woods-Saxon distribution inside Woods-Saxon distribution inside

nucleus nucleus deviation at very low amplitude deviation at very low amplitude

expected due to non-nuclear expected due to non-nuclear (electromagnetic) processes(electromagnetic) processes

b

centralperipheral


Bulk observables: Bulk observables: multiplicity and volumemultiplicity and volume

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Particle multiplicityParticle multiplicity

most central collisions at LHC: ~ 1600 charged particles per unit most central collisions at LHC: ~ 1600 charged particles per unit of of ηη

√sNN=2.76 TeV Pb+Pb, 0-5% central, |η|<0.5

dNch/dη / (<Npart>/2) = 8.3 0.4 (sys.)

ALICE: PRL105 (2010) 252301

log extrapolation:log extrapolation: OK at lower energiesOK at lower energies finally fails at the LHCfinally fails at the LHC


Bjorken’s formulaBjorken’s formula To evaluate the energy density reached in the collision:To evaluate the energy density reached in the collision:

for central collisions at LHC:for central collisions at LHC: GeV 1800oy

T

dy

dE

00

1

y

T

dy

dE

Sc

Initial time Initial time 00 normally taken to be ~ 1 fm/c normally taken to be ~ 1 fm/c i.e. equal to the “formation time”: the time it takes for the energy i.e. equal to the “formation time”: the time it takes for the energy

initially stored in the field to materialize into particlesinitially stored in the field to materialize into particles

Transverse dimension:Transverse dimension: fm)2.1( fm 160 3/12 ARS A

33 GeV/fm 10~GeV/fm )160/1800(~ More than enoughMore than enough

for for deconfinementdeconfinement

!!

c

S

fm/ 1~time"formation "

nucleus ofdimension transverse

0


Hanbury Brown - Twiss Hanbury Brown - Twiss interferometryinterferometry

quantum phenomenon: quantum phenomenon: enhancement of correlation enhancement of correlation function for identical bosonsfunction for identical bosons

from Heisenberg’s uncertainty from Heisenberg’s uncertainty principle:principle: ΔΔp · p · ΔΔxx ~ ħ ~ ħ (Planck’s constant)(Planck’s constant) (width of enhancement) · (source size) (width of enhancement) · (source size) ~ ~

ħħ extract source size from correlation extract source size from correlation

functionfunction first used with photons in the 1950s by first used with photons in the 1950s by

astronomers Hanbury Brown and Twiss astronomers Hanbury Brown and Twiss measured size of star Sirius by aiming at it two measured size of star Sirius by aiming at it two

photomultipliers separated by a few metresphotomultipliers separated by a few metres

e.g.: three components of e.g.: three components of correlation function C(q = correlation function C(q = momentum difference) for pairs of momentum difference) for pairs of pions for eight intervals of pair pions for eight intervals of pair transverse momentum (ktransverse momentum (kTT))


HBT interferometryHBT interferometry

from RHIC to LHC: from RHIC to LHC: increase of size in the 3 dimensionsincrease of size in the 3 dimensions

out, long, and (finally!) sideout, long, and (finally!) side

““homogeneity” volume ~ x 2homogeneity” volume ~ x 2Rout

Rside

Rlong

ALICE: Phys Lett B 696 (2011) 328


Strangeness enhancementStrangeness enhancement

3131

Historic QGP predictionsHistoric QGP predictions

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 s quarkscan be built recombining s quarks 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]

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The QGP strangeness abundance is enhancedThe QGP strangeness abundance is enhanced

As the QGP cools down, eventually the quarks recombine into As the QGP cools down, eventually the quarks recombine into hadrons (“hadronization”)hadrons (“hadronization”)

The abundance of strange hadrons should also be enhancedThe abundance of strange hadrons should also be enhanced

The enhancement should be larger for particles of higher The enhancement should be larger for particles of higher strangeness content, e.g.:strangeness content, e.g.:

E() > E() > E()

|s| = 3 |s| = 2 |s| = 1(sss) (sud)(ssd)


Strangeness enhancement at the Strangeness enhancement at the SPSSPS

Enhancement in Pb-Pb relative to p-Be Enhancement in Pb-Pb relative to p-Be (WA97/NA57)(WA97/NA57)

Enhancement 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


Strangeness enhancement: SPS. RHIC. LHCStrangeness enhancement: SPS. RHIC. LHC

enhancement decreases with increasing √senhancement decreases with increasing √s strange/non-strange increases with strange/non-strange increases with √s √s in ppin pp


Particle correlationsParticle correlations

3636

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-

plan

e

Y

XFlow

Flow

Reactionplane

In-planeOut

-of-

plan

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Y

XFlow

Flow

Reactionplane

In-planeOut

-of-

plan

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Y

XFlow

Flow


Azimuthal AsymmetryAzimuthal Asymmetry

@RHIC:@RHIC: at low pat low pTT: azimuthal asymmetry : azimuthal asymmetry

almost as large as expected at almost as large as expected at hydro limit! hydro limit! ““perfect liquid”?perfect liquid”?

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

...)2cos(2)cos(212

121

vv

dydpp

dN

dyddpp

dN

TTTT

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

Fourier expansion of azimuthal distribution:Fourier expansion of azimuthal distribution:


vv2 2 at the LHCat the LHC

vv22 still large at the LHC still large at the LHC

system still behaves very system still behaves very close to ideal liquid (low close to ideal liquid (low viscosity)viscosity)

vv22(p(pTT) very similar at LHC and ) very similar at LHC and RHICRHIC

similar hydrodynamical similar hydrodynamical behaviour?behaviour?

ALICE: PRL 105 (2010) 252302


Structures in (Structures in (ΔηΔη,,ΔφΔφ))


near side jet peak

long range structure in η on near sideaka “the ridge”

two shoulders on away side

(at 120 and 240 )aka “the Mach cone”

Mach cone?Mach cone? a proposed explanation: a proposed explanation:

shock wave (sonic boom) : shock wave (sonic boom) : propagation through medium propagation through medium of recoiling parton of recoiling parton

[Casalderrey-Solana, et al.: hep-ph/0411315]

double-hump structure on double-hump structure on away-side, at 120away-side, at 120 and 240 and 240


““ideal” shape of participants’ ideal” shape of participants’ overlap is ~ ellipticoverlap is ~ elliptic in particular: no odd harmonics expectedin particular: no odd harmonics expected participants’ plane coincides with event participants’ plane coincides with event

planeplane

but fluctuations in initial conditions:but fluctuations in initial conditions: participants plane participants plane event plane event plane vv3 3 (“triangular”) harmonic appears(“triangular”) harmonic appears

[B Alver & G Roland, PRC81 (2010) [B Alver & G Roland, PRC81 (2010) 054905]054905]

and indeed, and indeed, v3 v3 0 0 !! vv33 has weaker centrality has weaker centrality

dependence than dependence than vv22

when calculated wrt participants when calculated wrt participants plane, plane, vv33 vanishes vanishes as expected, if due to fluctuations…as expected, if due to fluctuations…

Fluctuations Fluctuations v v33

Matt Luzum (QM 2011)

ALICE: PRL 107 (2011) 032301

v2

v3


Long-Long-ηη-range correlations-range correlations

““ultra-central” events: dramatic ultra-central” events: dramatic shape evolution in a very narrow shape evolution in a very narrow centrality rangecentrality range

double hump structure on away-double hump structure on away-side appears on 1% most centralside appears on 1% most central visible without any need for vvisible without any need for v2 2

subtraction!subtraction!

first five harmonics describe first five harmonics describe shape at 10shape at 10-3-3 level level ““ridge” and “Mach cone”ridge” and “Mach cone” explanations based on medium explanations based on medium

response to propagating partons response to propagating partons were proposed at RHICwere proposed at RHIC

Fourier analysis of new data Fourier analysis of new data suggests very natural alternative suggests very natural alternative explanation in terms of explanation in terms of hydrodynamic response to initial hydrodynamic response to initial state fluctuationsstate fluctuations

Andrew Adare – ALICE (QM2011)


ALICE: Phys. Lett. B 708 (2012) 249

Correlations: outlookCorrelations: outlook

is there any residual room for medium response is there any residual room for medium response effects?effects?

look at the “small print” on the away sidelook at the “small print” on the away side

quantitative comparisons with full hydrodynamic quantitative comparisons with full hydrodynamic calculationscalculations


From Heavy Ions From Heavy Ions to Quark Matterto Quark Matter

Episode 2Episode 2Federico AntinoriFederico Antinori

(INFN Padova, Italy & CERN, Geneva, Switzerland)(INFN Padova, Italy & CERN, Geneva, Switzerland)4545

High-pHigh-pTT suppression suppression

4646

Participants Scaling vs Binary Participants Scaling vs Binary ScalingScaling

““Soft”, large cross-section processes expected to scale like NSoft”, large cross-section processes expected to scale like Npartpart

““Hard”, low cross-section processes expected to scale like NHard”, low cross-section processes expected to scale like Nbinbin

Npart (or Nwound) = 7 “participants”Nbin (or Ncoll) = 12 “binary collisions”

e.g.:


The nuclear modification factorThe nuclear modification factor

quantify departure from binary scaling in AAquantify departure from binary scaling in AA

ratio of yield in AA versus reference collisionsratio of yield in AA versus reference collisions

e.g.: reference is pp e.g.: reference is pp R RAAAA

……or peripheral AA or peripheral AA Rcp (“central to peripheral”) Rcp (“central to peripheral”)

AApp

AAAA

1

Yield

Yield

NbinR

central AA,

periphAA,

periph AA,

central AA,cp Yield

Yield

Nbin

NbinR


High pHigh pTT suppression: R suppression: RAA AA at RHICat RHIC

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

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

Interpreted as due to loss Interpreted as due to loss of energy of partons of energy of partons propagating through propagating through mediummedium


RRAAAA at the LHC at the LHC

)(Yield

)(Yield)(

ppAA

AAAA

T

TT pNbin

ppR

Suppression even larger Suppression even larger than @ RHICthan @ RHIC

RRAAAA(p(pTT) for charged particles ) for charged particles produced in 0-5% centrality produced in 0-5% centrality range range minimum (~ 0.14) for pminimum (~ 0.14) for pTT ~ 6-7 ~ 6-7

GeV/cGeV/c then slow increase at high pthen slow increase at high pTT still significant suppression still significant suppression

at p at pT T ~ 100 GeV/c !~ 100 GeV/c !

essential quantitative essential quantitative constraint for parton energy constraint for parton energy loss models!loss models!

compiled in: CMS: EPJC 72 (2012) 1945 5050FA - XVI Frascati Spring School - 7 to 11 May 2012

Suppression vs event planeSuppression vs event plane

significant effect, even at 20 GeV!significant effect, even at 20 GeV! further constraints to energy loss modelsfurther constraints to energy loss models

path-length dependence of energy loss (Lpath-length dependence of energy loss (L22, L, L33, …), …)

Alexandru Dobrin – ALICE (QM2011)


Quark number scalingQuark number scaling

5252

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 5353FA - XVI Frascati Spring School - 7 to 11 May 2012

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

Yield

Ncoll

NcollR

at higher pat higher pT, T, Rcp of baryons Rcp of baryons also comes down!also comes down!


Quark Recombination?Quark 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

quark number scalingquark number scaling

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-

S.Bass @ SQM`04


Quark number scaling and vQuark number scaling and v22

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

STAR Preliminary

scaled with n(quarks)

...)2cos(2)cos(212

121

vv

dydpp

dN

dyddpp

dN

TTTT

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


Identified particlesIdentified particles

5757

comparison of identified particle spectra with hydro predictionscomparison of identified particle spectra with hydro predictions

(calculations by C Shen et al.: arXiv:1105.3226 [nucl-th])(calculations by C Shen et al.: arXiv:1105.3226 [nucl-th])

OK for OK for ππ and and KK, but, but p p seem to “misbehave” (less yield, flatter spectrum)seem to “misbehave” (less yield, flatter spectrum)

ppTT spectra vs hydrodynamics spectra vs hydrodynamics

Michele Floris – ALICE (QM2011)


vv22 vs hydrodynamics vs hydrodynamics

comparison of identified particles vcomparison of identified particles v22(p(pTT) with hydro prediction) with hydro prediction

(calculation by C Shen et al.: arXiv:1105.3226 [nucl-th])(calculation by C Shen et al.: arXiv:1105.3226 [nucl-th])

again, protons are off… again, protons are off… what’s going on with protons? what’s going on with protons?

to be continued…to be continued…

Raimond Snellings ALICE (QM2011)


QuarkoniaQuarkonia

6060

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


J/J/ suppression pattern at the SPS suppression pattern 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/

NA50


J/J/ψψ suppression at RHIC suppression at RHIC

J/ψ ~ as suppressed as J/ψ ~ as suppressed as at SPS (NA50)at SPS (NA50)

[Hugo Pereira (PHENIX), QM05]


LHC: |y| < 2.4, pLHC: |y| < 2.4, pTT > 6.5 GeV/c (CMS) > 6.5 GeV/c (CMS)prompt J/prompt J/ψ ψ

more suppressed thanmore suppressed than

RHIC: |y| < 1. pT > 5 GeV/c (STAR)RHIC: |y| < 1. pT > 5 GeV/c (STAR)inclusive J/inclusive J/ ψ ψ

J/J/ψψ @ LHC: high p @ LHC: high pTT

LHC |y| < 2.5, pT > 3 GeV/c LHC |y| < 2.5, pT > 3 GeV/c (ATLAS) (ATLAS)

ATLAS: PLB 697 (2011) 294


CMS: arXiv:1201.5069

less suppression than less suppression than RHIC: 1.2 < y < 2.2, pRHIC: 1.2 < y < 2.2, pTT > 0 > 0 (PHENIX)(PHENIX)

~ as suppressed as ~ as suppressed as

RHIC: |y| < 0.35. pT > 0 (PHENIX)RHIC: |y| < 0.35. pT > 0 (PHENIX)

J/J/ψψ @ LHC: low p @ LHC: low pTT

• LHC: 2.5 < y < 4, pT > 0 (ALICE)


• very flat as a function of Nvery flat as a function of Npartpart

recombination at low precombination at low pTT??

ΥΥ(1S) suppression(1S) suppression



ΥΥ(2S+3S) suppression!(2S+3S) suppression!

additional suppression for additional suppression for ΥΥ(2S+3S) w.r.t. (2S+3S) w.r.t. ΥΥ(1S) ? (1S) ?

CMS: arXiv: 1105.4894


Quarkonia: outlookQuarkonia: outlook

the future runs should allow us to establish the future runs should allow us to establish quantitatively the complete quarkonium quantitatively the complete quarkonium suppression(/recombination?) pattern suppression(/recombination?) pattern high statistic measurementshigh statistic measurements open flavour baseline / contaminationopen flavour baseline / contamination pA baselinepA baseline


JetsJets

6969

Di-jet imbalanceDi-jet imbalance Pb-Pb events with large di-jet imbalance observed at the LHCPb-Pb events with large di-jet imbalance observed at the LHC

recoiling jet strongly quenched!recoiling jet strongly quenched!CMS: arXiv:1102.1957


imbalance quantified by the di-jet asymmetry variable imbalance quantified by the di-jet asymmetry variable AAJ J ::

AAJJ

with increasing centrality: with increasing centrality: enhancement of asymmetric di-enhancement of asymmetric di-

jets with respect to ppjets with respect to pp & HIJING + PYTHIA simulation& HIJING + PYTHIA simulation

8.2 4.0 R

ATLAS: PRL105 (2010) 252303


Di-jet Di-jet ΔφΔφ no visible angular decorrelation in no visible angular decorrelation in Δφ Δφ wrt pp collisions!wrt pp collisions!

large imbalance effect on jet energy, but very little effect on jet large imbalance effect on jet energy, but very little effect on jet direction!direction!



Jet nuclear modification factorJet nuclear modification factor

substantial suppression of jet substantial suppression of jet production production in central Pb-Pb wrt binary-scaled in central Pb-Pb wrt binary-scaled

peripheralperipheral

out to very large jet energies!out to very large jet energies!

PeripheralPeripheral

CentralCentralCP Nbin

NbinR

Yield

Yield

Brian Cole – ATLAS (QM2011)


Jet fragmentation functionJet fragmentation function

distribution of the momenta of the fragments along the jet axisdistribution of the momenta of the fragments along the jet axis

jetT

hadronT

E

Rpz

)cos(

peripheral

central

distribution is very distribution is very similar in central and similar in central and peripheral eventsperipheral events although quenching is although quenching is

very different…very different… apparently no effect apparently no effect

from quenching from quenching inside the jet cone…inside the jet cone…

another puzzle ?another puzzle ?Brian Cole – ATLAS (QM2011)


What next?What next? understand theoretically what is going onunderstand theoretically what is going on

strong di-jet asymmetrystrong di-jet asymmetry no visible effects in fragmentation function, dijet angular no visible effects in fragmentation function, dijet angular

correlations…correlations… /Z-jet fragmentation functions/Z-jet fragmentation functions

measure fragmentation function of jets recoiling against measure fragmentation function of jets recoiling against vector bosons vector bosons low-bias estimate of jet energy before low-bias estimate of jet energy before quenchingquenching

explore the surroundings of away-side jetsexplore the surroundings of away-side jets broadening? softening? re-heating?broadening? softening? re-heating?

in-medium fragmentation vs reaction planein-medium fragmentation vs reaction plane path length dependence!path length dependence!

b-tagged jets (quark vs gluon jets)b-tagged jets (quark vs gluon jets) extreme suppression?extreme suppression?

““mono-jet” events? what do they look like? mono-jet” events? what do they look like?


Heavy flavoursHeavy flavours

7676

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/ 7777FA - XVI Frascati Spring School - 7 to 11 May 2012

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 factor

transport coefficient of the medium

average energy lossdistance travelled in the medium

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


Experimentally: at RHICExperimentally: at RHIC

HF e ~ as suppressed as HF e ~ as suppressed as light hadronslight hadrons

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]


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 HF e contributions to RHIC HF e samples (no heavy flavour samples (no heavy flavour vertex detectors in RHIC vertex detectors in RHIC experiments)experiments)

[A. Suaide QM06]


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, CMSSilicon Pixels in ALICE, ATLAS, CMS

+ Silicon Vertex upgrades in STAR, PHENIX+ Silicon Vertex upgrades in STAR, PHENIX


Track Impact ParameterTrack Impact Parameter

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

e.g.: de.g.: d00 resolution in ALICE resolution in ALICE


Reconstructed D decaysReconstructed D decays

strong suppression observed in strong suppression observed in central Pb-Pb (0-20%) with respect to central Pb-Pb (0-20%) with respect to scaled pp referencescaled pp reference


Comparison: D and Comparison: D and ππ suppression suppression

charm is substantially suppressed: charm is substantially suppressed: in central collisions: ~ a factor 4-5 for pin central collisions: ~ a factor 4-5 for pT T > 5 GeV/c> 5 GeV/c

D meson RD meson RAAAA ~ compatible with ~ compatible with ππ R RAAAA

0-20% 40-80%


How about the colour factor?How about the colour factor?

quarks (Cquarks (CRR = 4/3) expected to = 4/3) expected to couple weaker than gluons (Ccouple weaker than gluons (CRR = 3)= 3)

at pat pTT ~ 8 GeV, factor ~ 2 less ~ 8 GeV, factor ~ 2 less suppression expected for D suppression expected for D than for light hadrons in gluon than for light hadrons in gluon radiation energy loss predictionradiation energy loss prediction

… to be continued with higher statistics…

N Armesto et al., Phys. Rev. D71 (2005) 054027


c and b quenching @ LHCc and b quenching @ LHC

substantial suppression of heavy flavour production– beauty, too!

with larger statistics: study parton mass and colour charge dependence of interaction with medium!


different parton different parton distribution functions in protons and distribution functions in protons and nucleinuclei

Gluon shadowing…Gluon shadowing…

[K J Eskola et al: JHEP04(2009)065]


a priori, large uncertainty measure p-Pb collisions!!!

x = fraction of nucleon momentum carried by gluon

EPSEPS0808 ( (redred) lies at low end of EPS) lies at low end of EPS0909 gluon PDF uncertainty gluon PDF uncertainty bandband inclusion of BRAHMS high rapidity datainclusion of BRAHMS high rapidity data

FA - XVI Frascati Spring School - 7 to 11 May 2012

EPSEPS0808 has largest shadowing has largest shadowing

8888

e.g.: for charm we have to be careful below e.g.: for charm we have to be careful below 1010 GeV or so p GeV or so pTT

Expected effects for charmExpected effects for charm


Calculation by Andrea Dainese

8989

p-Pb collisions in the LHC!p-Pb collisions in the LHC!

tricky, but can be done…tricky, but can be done… 2-in-1 design…2-in-1 design…

identical bending field in two beamsidentical bending field in two beams locks the relation between thelocks the relation between the

two beam momenta:two beam momenta:

p (Pb) = Z p(proton)p (Pb) = Z p(proton) different speeds for the two beams!different speeds for the two beams!

adjust length of closed orbits!adjust length of closed orbits! to compensate different speedsto compensate different speeds

different RF freq for two beams at injection and rampsdifferent RF freq for two beams at injection and ramps first p-Pb run scheduled for November 2012first p-Pb run scheduled for November 2012

estimated luminosity: 10estimated luminosity: 102828 – 10 – 102929 cm cm-2-2 s s-1-1


Heavy Flavour: outlookHeavy Flavour: outlook

high statistics D measurementshigh statistics D measurements are D really as suppressed as light hadrons?are D really as suppressed as light hadrons?

charm thermalisation?charm thermalisation? measure D mesons v2measure D mesons v2

subtract D background subtract D background pure B electron spectrum pure B electron spectrum beauty energy loss in wide pbeauty energy loss in wide pTT range range

in-medium fragmentation of b-tagged jets !in-medium fragmentation of b-tagged jets !


ConclusionsConclusions

in November 2010, the field of ultrarelativistic nuclear collisions in November 2010, the field of ultrarelativistic nuclear collisions has entered a new era with the start of heavy ion collisions at the has entered a new era with the start of heavy ion collisions at the LHCLHC abundance of hard probesabundance of hard probes state-of-the art collider detectorsstate-of-the art collider detectors

exciting results already from 2010 data sampleexciting results already from 2010 data sample death of ridge and Mach cone?death of ridge and Mach cone? anomalies in proton yields & momentum distributionsanomalies in proton yields & momentum distributions pattern of jet and heavy flavour suppression pattern of jet and heavy flavour suppression challenge to Eloss models challenge to Eloss models

and the future looks bright!and the future looks bright! ~ 150/µb delivered by LHC in 2011~ 150/µb delivered by LHC in 2011 p-Pb run scheduled for 2012p-Pb run scheduled for 2012 precision measurements + handle on cold nuclear matter effectsprecision measurements + handle on cold nuclear matter effects close in on dynamic and coupling properties of mediumclose in on dynamic and coupling properties of medium and … and … look out for surpriseslook out for surprises!!!!!!


Thank you!Thank you!

9393


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From Heavy Ions to Quark Matter Episode 1 Federico Antinori (INFN Padova, Italy & CERN, Geneva,...

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