[PPT] - Studies of deconfined matter at the LHC with ALICE A. Andronic GSI PowerPoint Presentation

SLIDE 1

Studies of deconfined matter at the LHC with ALICE

A. Andronic – GSI Darmstadt
n behalf of the ALICE Collaboration
Introduction: hot QCD (quark-gluon) matter; ALICE apparatus
Hadrons with light-flavor (u,d,s) and the QCD phase diagram
Quarkonium and deconfined matter
Jet quenching (if time allows)
Summary

56th International Winter Meeting on Nuclear Physics - Bormio, Jan. 22-27 2018

SLIDE 2

Lattice QCD predicts a phase transition

2

A. Andronic - ALICE

3p/T4 ε/T4 3s/4T3 4 8 12 16 130 170 210 250 290 330 370 T [MeV]

HRG non-int. limit Tc

hadrons (pions) εhad/T 4 = 3π2

30

(ideal gas) quarks and gluons εqg/T 4 = (16 + 7

812Nf)π2 30

Nf=3 (u,d,s) ≃1000 billion K see e.g: A. Bazavov et al., arXiv:1701.04325

transition is a crossover, Y. Aoki et al., Nature 443 (2006) 675 Tc ≃145-164 MeV, εc ≃ (0.18 − 0.5) GeV/fm3, or (1.2-3.1)εnuclear

numerical solutions of QCD on a discrete space-time grid (sophisticated formalism, huge computers)

SLIDE 3

.

SLIDE 4

How to ”simulate” in laboratory the early Universe?

4

A. Andronic - ALICE

initial state pre-equilibrium QGP and hydrodynamic expansion hadronization hadronic phase and freeze-out

t ≃ 10−23 s, V ≃ 10−40 m3

1. initial collisions (t ≤ tcoll = 2R/γcmc; RPb ≃7 fm)
2. thermalization: equilibrium is established (t 1 fm/c = 3 × 10−24 s)
3. expansion (∼ 0.6c) and cooling (t < 10-15 fm/c) ...deconfined stage?
4. hadronization (quarks and gluons form hadrons)
5. chemical freeze-out: inelastic collisions cease; particle identities (yields) frozen
6. kinetic freeze-out: elastic collisions cease; spectra are frozen (t+ = 3-5 fm/c)

SLIDE 5

What are the ”control parameters”

5

A. Andronic - ALICE
Energy of the collision (per nucleon pair, √sNN)
Centrality of the collision (number of “participating” nucleons, Npart)

[at high energies geometric concepts valid: “participant-spectator” picture] measured in percentage of the geometric cross section (σAB = π(RA + RB)2) NB: we sort the collisions offline, based on detector signals

)

PbPb

σ Centrality range (% of

coll

, N

part

N

10

2

10

3

10 =63 mb)

inel NN

σ =2.76 TeV (

NN

s Pb-Pb

part

N

coll

N

0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90

...while often taking as reference the measurement in proton-proton collisions (at the same energy), for “hard probes” (pQCD) scaled by the number of col- lisions corresponding to the given centrality class

SLIDE 6

The accelerator complex at CERN

6

A. Andronic - ALICE

SLIDE 7

The accelerator complex at CERN

7

A. Andronic - ALICE

SLIDE 8

The ALICE apparatus

8

A. Andronic - ALICE

arXiv:1402.4476 ALICE Collaboration: 37 countries, 176 institutions, 1800 members 8

A. Andronic - ALICE

SLIDE 9

Nucleus-nucleus collisions at the LHC

9

A. Andronic - ALICE

a picture of a central collision (about 3200 primary tracks in |η| < 0.9); “Camera”: Time Projection Chamber [ 5 m length, 5 m diam.; 500 mil. pixels; we take a few 100 pictures per second (and are preparing to take 50000) ]

SLIDE 10

Nucleus-nucleus collisions: energy density

10

A. Andronic - ALICE

(GeV)

NN

s 1 10

2

10

3

10

4

10 (GeV) 〉 /2

part

N 〈 / 〉 η /d

T

E d 〈 2 4 6 8 10 12 14 16

/b)

NN

s a ln(

ALICE Preliminary ALICE PRC94(2016)034903 CMS STAR PHENIX NA49 E802/E917 WA98

b

a s

ALI-PREL-118376

ET: transverse energy (energy built from pT) εLHC ≃ 20 − 40 GeV/fm3 (much above εc) εFAIR 1 GeV/fm3 (around εc)

self-similar (Hubble-like) homogeneous (hydrodynamic) expansion of the fireball in the longitudinal (beam) direction (”Bjorken model”, J.D. Bjorken, PRD 27 (1983) 140)

Energy density: ε =

1 AT dET dy 1 cτ

AT = πR2: transverse area (Pb-Pb: AT =154 fm2)
τ ≃1 fm/c: formation time (establishing the equilibrium) ...not measurable!

SLIDE 11

Particle identification

11

A. Andronic - ALICE

dE/dx: truncated mean of 159 samples along a track; resolution: 5.8% lines: Bethe-Bloch parametrization particles and antiparticles are shown

SLIDE 12

Hadron yields

12

A. Andronic - ALICE

y /d N Yield d

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 =2.76 TeV, 0-10% centrality

NN

s Pb-Pb Data, ALICE Data, ALICE

+

π

π

+

K

K

s

K φ p p Λ Λ

Ξ

+

Ξ

Ω

+

Ω d d He

3

He

3

H

Λ 3

H

Λ 3

He

4

He

4

Matter and antimatter are produced in equal amounts in high-energy Pb-Pb collisions at the LHC Mass hierarchy in production

arXiv:1710.07531

SLIDE 13

Hadron yields and statistical hadronization

13

A. Andronic - ALICE

y /d N Yield d

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 =2.76 TeV, 0-10% centrality

NN

s Pb-Pb =2.76 TeV, 0-10% centrality

NN

s Pb-Pb Data, ALICE Statistical Hadronization Data, ALICE Statistical Hadronization

+

π

π

+

K

K

s

K φ p p Λ Λ

Ξ

+

Ξ

Ω

+

Ω d d He

3

He

3

H

Λ 3

H

Λ 3

He

4

He

4

Data/Model

0.5 1 1.5 2

+

π

π

+

K

K

s

K φ p p Λ Λ

Ξ

+

Ξ

Ω

+

Ω d d He

3

He

3

H

Λ 3

H

Λ 3

He

4

He

4

Matter and antimatter are produced in equal amounts in high-energy Pb-Pb collisions at the LHC Best fit: TCF = 156.5 ± 1.5 MeV µB = 0.7 ± 3.8 MeV V = 5280 ± 410 fm3 chemical freeze-out Laboratory creation of a piece

f hot Universe when 10 µs
ld, T ≃ 1012 K

arXiv:1710.07531 arXiv:1710.09425

SLIDE 14

Thermal fit of hadron abundances

14

A. Andronic - ALICE

ni = Ni/V = −T V ∂ ln Zi ∂µ = gi 2π2 ∞ p2dp exp[(Ei − µi)/T] ± 1

quantum nr. conservation ensured via chemical potentials: µi = µBBi + µI3I3i + µSSi + µCCi Latest PDG hadron mass spectrum (up to 3 GeV, 500 species) Minimize: χ2 =

i (Nexp

i

−Ntherm

i

)2 σ2

i

Ni: hadron yield ⇒ (T, µB, V )

Mass (GeV)

0.5 1 1.5 2 2.5 3 3.5 4

+1) J /(2 y /d N d

7 −

10

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 Data, ALICE Statistical Hadronization total (after decays) primordial

=2.76 TeV

NN

s Pb-Pb

0-10% centrality

+

π

+

K p φ Λ

Ξ
Ω

d He

3

H

Λ 3

He

4

The hadron abundances are in agreement with a chemically-equilibrated system ...but how can a loosely-bound deuteron “survive” at T=156 MeV?

SLIDE 15

Chemical freeze-out and the phase diagram of QCD

15

A. Andronic - ALICE

← − √sNN (GeV)

2760 200 20 5 2.3

20 40 60 80 100 120 140 160 180 200 1 10 10

2

10

3

µB (MeV) T (MeV)

Statistical Hadronization, TCF

Quark-Gluon Matter Hadronic Matter Nuclei

Lattice QCD, Tc Borsanyi et al.; HotQCD Collab. Cleymans, Redlich Becattini et al. Vovchenko et al. Andronic et al. STAR Collab.

arXiv:1710.09425

at LHC, remarkable “coincidence” with Lattice QCD results at LHC (µB ≃ 0): purely-produced (anti)matter (m = E/c2), as in the Early Universe µB > 0: more matter, from “rem- nants” of the colliding nuclei µB 400 MeV: the critical point awaiting discovery µB is a measure of the net-baryon density, or matter-antimatter asym- metry

SLIDE 16

Proton collisions at the LHC

16

A. Andronic - ALICE

pp collision at 7 TeV, “photographed” by ALICE

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Proton collisions at the LHC

17

A. Andronic - ALICE

pp collision at 7 TeV, “photographed” by ALICE

SLIDE 18

Hyperon production - from small to large systems

18

A. Andronic - ALICE

ALI-PUB-106878

Nature Physics 13 (2017) 535

(big geometric) fireball in Pb–Pb reached with violent pp and p–Pb collisions (grand canonical) statistical description works well in Pb–Pb (with T of QCD phase boundary) is the same mechanism at work in small systems (at large multiplicities)? string hadronization models do not describe data well ...new ideas are being put forward

Fischer, Sj¨

strand, JHEP 01 (2017) 140

“thermodynamical string fragmentation”

SLIDE 19

Fluctuations of relative hadron production

19

A. Andronic - ALICE

quantified by νdyn[A, B] =

NA(NA−1) NA2

+ NB(NB−1)

NB2

− 2 NANB

NANB

the relative strength of fluctuations of species A and B - relative strength of cor- relations between species A and B (event-by-event) νdyn[A, B] = 0 if A and B are produced in a statistically independent way

arXiv:1712.07929

]

+K

+

,K

π

+

π [

dyn

ν 1 2 3

3 −

10 ×

ALICE: 0-5% Pb-Pb (Identity Method), stat. uncertainty Systematic uncertainty c <1.5 GeV/ p |<0.8, 0.2< η | STAR: 0-5% Au-Au (TPC+TOF) c <1.8 GeV/ p 0.2, ≥

T

p , K: π |<1, η | c <3.0 GeV/ p 0.4, ≥

T

p p: PRC92(2015)021901

] p ,p+

π

+

π [

dyn

ν 4 − 2 − 10 ×

= 2.76 TeV

NN

s ALICE Pb-Pb

(GeV)

NN

s 10

2

10

3

10

]

+K

+

,K p [p+

dyn

ν 4 − 2 − 10 ×

SLIDE 20

Collective flow

20

A. Andronic - ALICE
R. Snellings, arXiv:1102.3010

dN dϕ ∼ [1 + 2v1 · cos(ϕ) + 2v2 · cos(2ϕ) + ...] ϕ is azimuthal angle with respect to reaction plane v2 = cos(2ϕ) we call elliptic flow, v3 = cos(3ϕ) triangular flow (coefficients)

SLIDE 21

Data and hydrodynamics

21

A. Andronic - ALICE

) c (GeV/

T

p

0.5 1 1.5 2 2.5 3 3.5

/GeV) c ( y d

T

p /d N d

1 10

2

10

3

10 =2.76 TeV, 10-20%

NN

s Pb-Pb

Data, ALICE |<0.5 y | lines: hydrodynamics |<1.2 y VISHNU, |

+

π

+

K p

) c (GeV/

T

p

1 2 3 4 5

2

v Elliptic flow

0.05 0.1 0.15 0.2 0.25

)

s

K particles + antiparticles (incl.

mass dependence due to collective flow hydrodynamic models reproduce the data with a very small viscosity/entropy density, η/s (∼ Tλcs) lower bound conjectured (AdS/CFT): η/s ≥ 1/4π

Kovtun, Son, Starinets, PRL 94 (2005) 111601 Data: PRC 88 (2013) 044910 JHEP 06 (2015) 190 VISHNU: PRC 89 (2014) 034919

SLIDE 22

Elliptic flow: energy dependence

22

A. Andronic - ALICE
0.1
0.05

0.05 0.1 10 10

2

10

3

√sNN (GeV) v2 at mid-rapidity

ut-of-plane

in-plane mid-central collisions (<b>≈7 fm) (<Npart>≈160, <εpart>≈0.3)

FOPI (Z=1) E895, E877 (p) STAR (h±) PHOBOS (h±) ALICE (h±) CMS (h±) CERES (h±) NA49 (π±)

SIS AGS SPS RHIC LHC

PRL 116 (2016) 132302

v2 > 0 at high energies: “free” fireball (almond-shape) expan- sion (“genuine” elliptic flow) hydrodynamic description deter- mined by η/s and initial con- ditions (matter/energy fluctua- tions of colliding nuclei) ...constrained by correlations be- tween vn coeff., arXiv:1709.01127 we do also “event-shape engi- neering”, arXiv:1709.04723

SLIDE 23

Quark interlude

23

A. Andronic - ALICE

up to now we only considered hadrons built with u, d, s quarks ...these are light, masses from a few MeV (u, d) to ∼90 MeV (s) what about heavier ones? ...for instance c, which weights about 1.2 GeV produced in pairs (c¯ c) in initial hard collisions (t ∼ c/(2mc) ≤ 0.1 fm/c)

bservable: RAA =

dNAA/dpTdy Ncoll·dNpp/dpTdy, the nuclear modification factor

ne meson, the J/ψ (a bound state of c and ¯

c, charmonium) is of particular interest

SLIDE 24

Charmonium and deconfined matter

24

A. Andronic - ALICE

the original idea: Matsui & Satz, PLB 178 (1986) 178

”If high energy heavy-ion collisions lead to the formation of a hot quark-gluon-plasma, then color screening prevents c¯ c binding in the deconfined interior of the interaction region.”

Refinements: “sequential suppression”: Digal et al., PRD 64 (2001) 75 no q¯ q bound state if rq¯

q(T) > r0(T) ≃ 1/(g(T)T)

r0 Debye length in QGP ⇒ q¯ q “thermometer” of QGP

0.5 1 1.5 2 1 1.5 2 2.5 3 T/Tc J/ψ r0(T) Υ

Thermal picture (npartons = 5.2T 3 for 3 flavors) for T=500 MeV: np ≃84/fm3, mean separation ¯ r=0.2 fm < rJ/ψ

SLIDE 25

Models ...implementing Debye screening and more

25

A. Andronic - ALICE

Statistical hadronization model all charm quarks are produced in primary hard collisions (tc¯

c ∼ 1/2mc ≃ 0.1 fm/c)

...survive and thermalize in QGP (thermal, but not chemical equilibrium) charmed hadrons are formed at chemical freeze-out together with all hadrons “generation” ...no J/ψ survival in QGP (full screening) if supported by data, J/ψ looses status as “thermometer” of QGP ...and gains status as a powerful observable for the phase boundary

Braun-Munzinger, Stachel, PLB 490 (2000) 196; NPA 789 (2006) 334, PLB 652 (2007) 259

SLIDE 26

Models ...implementing Debye screening and more

26

A. Andronic - ALICE

Statistical hadronization model all charm quarks are produced in primary hard collisions (tc¯

c ∼ 1/2mc ≃ 0.1 fm/c)

...survive and thermalize in QGP (thermal, but not chemical equilibrium) charmed hadrons are formed at chemical freeze-out together with all hadrons “generation” ...no J/ψ survival in QGP (full screening) if supported by data, J/ψ looses status as “thermometer” of QGP ...and gains status as a powerful observable for the phase boundary

Braun-Munzinger, Stachel, PLB 490 (2000) 196; NPA 789 (2006) 334, PLB 652 (2007) 259

Transport models implement screening picture with space-time evolution of QGP (hydrodynamics) continuous destruction and “(re)generation” (“recombination”)

Thews et al., PRC 63 (2001) 054905 ... “TAMU”, PLB 664 (2008) 253, NPA 859 (2011) 114, EPJA 48 (2012) 72 “Tsinghua”, PLB 607 (2005) 107, PLB 678 (2009) 72, PRC 89 (2014) 054911 Strickland, Bazow, NPA 879 (2012) 25

SLIDE 27

Charmonium data at RHIC and the LHC

27

A. Andronic - ALICE

=0 η

| η /d

ch

dN

500 1000 1500 2000

ψ J/ AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

8% syst.unc.) ± =5.02 TeV (ALICE, 2.5<y<4.0,

NN

s 9% syst.unc.) ± =0.2 TeV (PHENIX, 1.2<y<2.2,

NN

s

dNch/dη ∼ ε (>20 GeV/fm3, for dNch/dη ≃ 2000)

ALICE, PLB 766 (2017) 212; PHENIX, PRC 84 (2011) 054912

RAA =

dNAA/dpTdy Ncoll·dNpp/dpTdy

nuclear modification factor

”suppression” at RHIC (PHENIX)
dramatically different at the LHC

.

SLIDE 28

Charmonium data at RHIC and the LHC

28

A. Andronic - ALICE

=0 η

| η /d

ch

dN

500 1000 1500 2000

ψ J/ AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

8% syst.unc.) ± =5.02 TeV (ALICE, 2.5<y<4.0,

NN

s 9% syst.unc.) ± =0.2 TeV (PHENIX, 1.2<y<2.2,

NN

s

lines: Statistical Hadronization Model

0.055 mb ± /dy = 0.344

c c

σ d

dNch/dη ∼ ε (>20 GeV/fm3, for dNch/dη ≃ 2000)

arXiv:1710.09425

RAA =

dNAA/dpTdy Ncoll·dNpp/dpTdy

nuclear modification factor

”suppression” at RHIC (PHENIX)
dramatically different at the LHC

Statistical Hadronization Model NJ/ψ ∼ (Ndir

c¯ c )2

J/ψ is another observable (charm) for the phase boundary calculations are for T=156 MeV

SLIDE 29

J/ψ data and the statistical model

29

A. Andronic - ALICE

〉

part

N 〈 50 100 150 200 250 300 350 400 450

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

= 5.02 TeV

NN

s Pb − ALICE Preliminary, Pb

e

+

e → ψ Inclusive J/ c > 0.15 GeV/

T

p | < 0.8, y |

Statistical hadronization (Andronic et al.) ALI−PREL−118543

〉

part

N 〈 50 100 150 200 250 300 350 400 450

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

= 5.02 TeV

NN

s Pb − ALICE, Pb

µ

+

µ → ψ Inclusive J/ c < 8 GeV/

T

p < 4, 0.3 < y 2.5 <

Statistical hadronization (Andronic et al.)

ALI-DER-111595

ALICE, PLB 766 (2017) 212

The statistical hadronization model assumes full thermalization of charm quarks, full dissociation of J/ψ mesons in QGP and formation at the hadronization within this model, the “thermometer” status is lost, but J/ψ (charm) becomes a remarkable observable for the QCD phase boundary (hadronization)

SLIDE 30

J/ψ data and transport models

30

A. Andronic - ALICE

〉

part

N 〈 50 100 150 200 250 300 350 400 450

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

= 5.02 TeV

NN

s Pb − ALICE Preliminary, Pb

e

+

e → ψ Inclusive J/ c > 0.15 GeV/

T

p | < 0.8, y |

Transport (TM1, Du and Rapp) Transport (TM2, Zhou et al.) ALI−PREL−118539

〉

part

N 〈 50 100 150 200 250 300 350 400 450

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

= 5.02 TeV

NN

s Pb − ALICE, Pb

µ

+

µ → ψ Inclusive J/ c < 8 GeV/

T

p < 4, 0.3 < y 2.5 < (TM1, Du and Rapp) c > 0.3 GeV/

T

p Transport, Transport (TM2, Zhou et al.)

ALI-DER-128819

ALICE, PLB 766 (2017) 212

Transport models assume continuous dissociation and formation during the whole lifetime of QGP (time evolution of T constrained by other measurements)

(employ smaller uncert. of dσc¯

c/dy)

SLIDE 31

J/ψ production vs. pT

31

A. Andronic - ALICE

) c (GeV/

T

p

2 4 6 8 10

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

, Centrality 0-20%

e

+

e → ψ Inclusive J/

= 5.02 TeV, |y| < 0.9 (Preliminary)

NN

s ALICE, Pb-Pb = 0.2 TeV, |y| < 0.35 PRL 98 (2007) 232301

NN

s PHENIX, Au-Au = 0.2 TeV, |y| < 1 PRC 90 (2014) 024906

NN

s STAR, Au-Au = 0.2 TeV, |y| < 1 PLB 722 (2013) 55-62

NN

s STAR, Au-Au ALI−PREL−141527

) c (GeV/

T

p 2 4 6 8 10 12

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

, 0-20% centrality

µ

+

µ → ψ Inclusive J/ < 4 y = 5.02 TeV, 2.5 <

NN

s Pb − ALICE, Pb < 4 y = 2.76 TeV, 2.5 <

NN

s Pb − ALICE, Pb | < 2.2 y = 0.2 TeV, 1.2 < |

NN

s Au − PHENIX, Au

ALI-DER-112463

ALICE, JHEP 06 (2015) 055

as expected, (re)generation is a low-pT phenomenon significantly different trend at the LHC compared to RHIC J/ψ at high-pT suppressed as consequence of charm energy loss in QGP

SLIDE 32

Charmonium production

32

A. Andronic - ALICE

Production of excited states crucial to investigate ...possible with HL-LHC

(GeV)

NN

s

10

2

10

3

10

4

10

) ψ (2S)/(J/ ψ Relative production

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22 pp Pb-Pb

statistical description, arXiv:1710.09425 ...transport models predict larger relative production

SLIDE 33

Summary

33

A. Andronic - ALICE
in nucleus-nucleus collisions we create a (small:) chunk of the hot early Universe

...a highly-dynamic and collective system; we measure observables for various stages

measured energy densities are well above the values expected for deconfinement
collective flow (developed early in the deconfined stage) described by hydrodynamics; allows extraction of η/s
abundance of hadrons with light quarks consistent with chemical equilibration

the thermal model provides a simple way to access the QCD phase boundary ...but is it more than a 1st order description (of loosely-bound objects)? ...and what fundamental point does it make about hadronization?

we see (re)combination of charm quarks at the LHC ...either over the full history of QGP or at the phase

boundary ...conclusion expected with the ALICE upgrade (HL-LHC, 2021-2029)

some of the features in heavy-ion collisions are observed in high-multiplicity pp and p–Pb collisions
not shown but available in spare slides

we measure strong jet quenching (parton energy loss) in quark-gluon matter jet quenching data (for light and heavy-flavor hadrons) described by theoretical models; allows extraction of transport coefficients (in range T = (1 − 3)Tc) More in talks by Ivan Vorobyev (Wed) and Jeremy Wilkinson (Fri)

SLIDE 34

Additional slides

A.Andronic

SLIDE 35

Overview of hadron production

1

A. Andronic - ALICE

10

1

1 10 10 2 10 3 10 10

2

10

3

√sNN (GeV) Yield dN/dy|y=0

Npart=350

AGS SPS RHIC LHC

π+ π- K+ K- p p

–

Λ Λ

–

lots of particles, mostly newly

created (m = E/c2)

a great variety of species:

π± (u ¯ d, d¯ u), m=140 MeV K± (u¯ s, ¯ us), m=494 MeV p (uud), m=938 MeV Λ (uds), m=1116 MeV also: Ξ(dss), Ω(sss)...

mass hierarchy in production

(u, d quarks: remnants from the incoming nuclei)

SLIDE 36

The grand (albeit partial) view at hadron production

2

A. Andronic - ALICE

2 3

yield ratio y /d N d

4 −

10

3 −

10

2 −

10

1 −

10 1 10

+

π p/

π

/ p d/p

Points: Data Lines: Statistical Hadronization

(GeV)

NN

s

10

2

10

3

10

yield ratio y /d N d

0.05 0.1 0.15 0.2 0.25

+

π /

+

K

π

/

K

+

π / Λ

Data: AGS: E895, E864, E866, E917, E877 SPS: NA49, NA44 RHIC: STAR, BRAHMS LHC: ALICE

NB: no contribution from weak decays

data consistent with smooth behaviour vs. energy

SLIDE 37

Mean transverse momentum of J/ψ mesons

3

A. Andronic - ALICE

〉

part

N 〈

1 10

2

10

AA

r

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

<4 y , 2.5<

µ

+

µ → ψ ALICE inclusive J/ = 2.76 TeV, global syst. = 4%

NN

s Pb-Pb

|<2.2 y , 1.2<|

µ

+

µ → ψ PHENIX inclusive J/ = 0.2 TeV, global syst. = 3%

NN

s Au-Au and Cu-Cu <1 y , 0<

µ

+

µ → ψ NA50 inclusive J/ = 0.017 TeV, global syst. = 3%

NN

s Pb-Pb Transport model calculations TM1 ALICE TM2 ALICE RHIC SPS

ALICE, JHEP 05 (2016) 179

rAA = p2

TAA

p2

Tpp

softening of pT is significant at the LHC, clear indication of (re)generation thermalization of charm quarks demonstrated by collective flow of D and J/ψ

SLIDE 38

J/ψ production vs. pT

4

A. Andronic - ALICE

) c (GeV/

T

p 1 2 3 4 5 6 7 8

PbPb

R ,

backw pPb

R x

forw pPb

R 0.2 0.4 0.6 0.8 1 1.2 1.4

µ

+

µ → ψ ALICE inclusive J/ = 5.02 TeV

NN

s <-2.96),

cms

y (-4.46<

backw pPb

R <3.53) x

cms

y (2.03<

forw pPb

R = 2.76 TeV, 0-90%

NN

s <4),

cms

y (2.5<

PbPb

R (Phys. Lett. B734 (2014) 314)

ALICE, JHEP 06 (2015) 055

Distinct differences between Pb–Pb and p–Pb; crucial support that low-pT J/ψ are from (re)generation (while at high-pT outcome of charm energy loss in QGP)

for mid-rapidity: Run 1 data stat.-limited; Run 2 data will bring significance

SLIDE 39

J/ψ and D mesons exhibit collective flow

5

A. Andronic - ALICE

) c (GeV/

T

p

2 4 6 8 10 12

{EP}

2

v

0.1 − 0.05 − 0.05 0.1 0.15 0.2 0.25 = 5.02 TeV

NN

s ALICE Pb-Pb,

1% ± global syst :

5-20% 40-60% 20-40%

arXiv:1707.01005

30-50%,

,

−

µ

+

µ → ψ Inclusive J/ < 4 y , 2.5 < = 1.1} η ∆ {EP,

2

v average,

*+

, D

+

, D Prompt D < 0.8  y  , = 0.9}  η ∆  {EP,

2

v

) c (GeV/

T

p

2 4 6 8 10 12

{EP}

2

v

0.1 − 0.05 − 0.05 0.1 0.15 0.2 0.25 = 5.02 TeV

NN

s ALICE 20 - 40% Pb-Pb,

ψ Inclusive J/

X. Du et al.

< 4) y (2.5 <

K. Zhou et al.

= 0} η ∆ {EP,

2

v | < 0.9, y , |

e

+

e = 1.1} η ∆ {EP,

2

v < 4, y , 2.5 <

µ

+

µ

global syst : 1%

| < 0.9 y |

, ψ Inclusive J/

< 4 y 2.5 <

, ψ Inclusive J/

< 4 y 2.5 <

, ψ Primordial J/ w non-collective ψ Inclusive J/ w/o non-collective ψ Inclusive J/ ψ Primordial J/

ALICE, PRL 119 (2017) 242301

Implies thermalization of charm quarks ...full thermalization? (high-pT?) ...and how to make distinction between statistical and dynamical production?

SLIDE 40

Charmonium production in p–Pb collisions

6

A. Andronic - ALICE

cms

y

5
4
3
2
1

1 2 3 4 5

pPb

R 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

µ

+

µ → (2S) ψ , ψ = 5.02 TeV, inclusive J/

NN

s ALICE, p-Pb ψ J/ (2S) ψ

EPS09 NLO (Vogt) /fm (Arleo et al.)

2

=0.075 GeV q ELoss with /fm (Arleo et al.)

2

=0.055 GeV q EPS09 NLO + ELoss with

ALICE, JHEP 12 (2014) 073

(at least in first order) models give same result for ψ(2S) as for J/ψ in data, difference predominantly at low pT

SLIDE 41

Probing early stages

7

A. Andronic - ALICE

...with ”hard probes” (m ≫ T): jets or high-pT hadrons (or heavy quarks) produced very early in the collision, t ≃ 1/m (jets - sprays of hadrons from high-speed quarks)

q, ¯

q, g travel through QGP, lose energy

hadronize (neutralize color picking up

partners from the vacuum)

hadrons fly towards detectors

...where we observe a deficit at high mo- menta (pT): ”jet quenching” (Bjorken, FERMILAB-PUB-82-059-T ) quantified by the nuclear modification factor: RAA =

dNAA/dpTdy Ncoll·dNpp/dpTdy

D. d’Enterria, arXiv:0902.2011

SLIDE 42

Jet quenching at the LHC

8

A. Andronic - ALICE

...measured with ”leading hadrons” (h±) (carry largest fraction of parton pT)

)

2

c ) or mass (GeV/ c (GeV/

T

p

10 20 30 40 50 60 70 80 90 100

pPb

R ,

PbPb

R

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

= 5.02 TeV, NSD (ALICE)

NN

s , p-Pb

±

h = 2.76 TeV, 0-10% (CMS)

NN

s , Pb-Pb γ = 2.76 TeV, 0-10% (CMS)

NN

s , Pb-Pb

±

W = 2.76 TeV, 0-10% (CMS)

NN

s , Pb-Pb Z = 2.76 TeV, 0-20% (ALICE)

NN

s , Pb-Pb γ (norm. to pQCD NLO calc., Vogelsang)

, Pb-Pb (ALICE)

±

h , Pb-Pb (CMS)

±

h

= 2.76 TeV, 0-5%

NN

s

a thermal component, pT 6 GeV/c (scaling with Npart) determined by gluon saturation and collec- tive flow

strong suppression, reaching a fac- tor of ∼7, pT ≃ 7 GeV/c ...not seen with EW observables (γ, W ±, Z0) ...ALICE γ / pQCD NLO calc. not seen in p-Pb collisions (pT 3 GeV/c, gluon saturation)

ALICE, EPJ C 74 (2014) 3054 and refs. therein

SLIDE 43

Jet quenching: transport coefficient

9

A. Andronic - ALICE

An initial quark with energy

f 10 GeV at the center of a

most-central A–A collision

JET Collab., PRC 90 (2014) 014909

transport coefficient: ˆ q = dp2

T/dx

(proportional to gluon density) The data of Run 2 (about to be published) are significantly more precise

SLIDE 44

In-medium energy loss as a function of quark mass

10

A. Andronic - ALICE

〉

part

N 〈

50 100 150 200 250 300 350 400

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

(empty) filled boxes: (un)correlated syst. uncert.

ψ (*) 50-100% for non-prompt J/

|<0.5 y , | c <16 GeV/

T

p D mesons (ALICE) 8<

= 2.76 TeV

NN

s Pb-Pb,

〉

part

N 〈 shifted by +10 in

±

π

(CMS) ψ Non-prompt J/ |<1.2 y , | c <30 GeV/

T

p 6.5<

EPJC 77 (2017) 252

50-80%* 40-50% 30-40% 20-30% 10-20% 0-10% |<0.8 y , | c <16 GeV/

T

p (ALICE) 8<

±

π

D mesons are as much suppressed as pions at high pT ...is expected ordering vs. quark mass ∆Eb < ∆Ec < ∆Eu,d,s < ∆Eg established in data? (naively: ∆E ∼ 1 − RAA) to some extent, yes

JHEP 11 (2015) 205 ALICE-PUBLIC-2017-004

n-going effort: determine heavy quark (momentum) diffusion coefficient

...calculable in lattice QCD Banerjee et al., Phys. Rev. D 85 (2012) 014510

SLIDE 45

In-medium energy loss as a function of quark flavor

11

A. Andronic - ALICE

〉

part

N 〈

50 100 150 200 250 300 350 400

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4

|<0.5 y , | c <16 GeV/

T

p D mesons (ALICE) 8< (empty) filled boxes: (un)correlated syst. uncert. |<0.5 y , | c <16 GeV/

T

p D mesons (ALICE) 8<

= 2.76 TeV

NN

s Pb-Pb,

(CMS) ψ Non-prompt J/ |<1.2 y , | c <30 GeV/

T

p 6.5<

EPJC 77 (2017) 252

ψ (*) 50-100% for non-prompt J/

50-80%* 40-50% 30-40% 20-30% 10-20% 0-10% MC@sHQ+EPOS2 D mesons ψ Non-prompt J/ with c quark energy loss ψ Non-prompt J/

Phys.Rev.C 89 (2014) 014905

Theoretical model(s) reproduce the data (reasonably) well

JHEP 11 (2015) 205 ALICE-PUBLIC-2017-004

SLIDE 46

Charm diffusion coefficient

12

A. Andronic - ALICE

heavy quark spatial diffusion coefficient Ds = 4T 2/ˆ q

arXiv:1704.07800

SLIDE 47

Jets

13

A. Andronic - ALICE

...in vacuum ...in medium E: ET or pT; θjet: opening angle (R or ∆R)

Y. Mehtar-Tani, arXiv:1602.01047

SLIDE 48

Advantage of heavy quarks

14

A. Andronic - ALICE

Their mass, mc ≃1.2 GeV, mb ≃4.6 GeV, is much larger than T (so we are sure they do not originate in thermal processes ...but pQCD processes) Are produced in pairs (c¯ c) in initial hard collisions (t ∼ 1/(2mc) ≤ 0.1 fm/c) Their identity (flavor) is assured to be preserved from early times of production throughout the QGP phase (until hadronization: c → D; b → B) Expectation: Due to high mass the gluon radiation by HQ is suppressed at small angles this is called ”the dead-cone effect” Consequence: hierarchy in energy loss: ∆Eb < ∆Ec < ∆Eu,d,s < ∆Eg At the LHC, there are about 100 c¯ c pairs produced in a central Pb–Pb collisions (not all are measurable, though)