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International School on: Quark-Gluon Plasma and Heavy Ion Collisions: Past, Present, Future Villa Gualino, Turino, Italy Soft Probes II. Christoph Blume University of Heidelberg. Observables. Temperature. Strangeness Resonances. Femtoscopy Fluctuations. Kinetic Freeze-Out.

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Christoph blume university of heidelberg

International School on:Quark-Gluon Plasma and Heavy Ion Collisions:Past, Present, FutureVilla Gualino, Turino, ItalySoft Probes II

Christoph Blume

University of Heidelberg








Kinetic Freeze-Out

Chemical Freeze-Out


Jets +

Heavy Flavor




Strangeness in heavy ion physics

Strangeness in Heavy Ion Physics

Strangeness enhancement as a QGP signature

J. Rafelski and B. Müller, PRL48, 1066 (1982)

P. Koch, B. Müller, and J. Rafelski, Phys. Rep. 142, 167 (1986)

Strangeness has to be produced (no s-Quarks in nucleons)

Thresholds are high in hadronic reactions,

e.g..: N + N  N + K+ +  (Ethres  700 MeV)

Fast equilibration in a QGP via partonic processes,

e.g. gluon-fusion

⇒ Enhancement of strange particle production in A+A relative

to p+p expected (in particular multi-strange particles)

Statistical models

Statistical Models

Multiplicities determined by

statistical weights

(⇒ chemical equilibrium)

Grand-canonical partition function:

⇒ Parameters: V, T, μB, γS

Details: see F. Becattini’s lecture

A.Andronic et al.

PLB673, 142 (2009)

F.Becattini et al.,

PRC69, 024905 (2004)

Hadronic transport models

Pb+Pb@ √sNN = 17.3 GeV


Hadronic Transport Models

Microscopic approach

Hadronic degrees of freedom


Production mechanisms:

Measured and parameterized

cross sections

String-excitation and fragmentation

Medium effects,

Multi-meson fusion,

Mass shifts,









Strange particles

Strange Particles

Major strangeness carriers kaons and lambdas

Strangeness Conservation




Isospin Symmetry

Isospin Symmetry

K+ (us)

K- (us)

K0 (ds)

 (uds)

K0 (ds)

Major Strangeness Carriers: Kaons and Lambdas



 (uds)

If baryon density is high

Measurement of charged kaons via de dx

Measurement of Charged Kaons via dE/dx

Bethe-Bloch function:

Combination of de dx and time of flight tof

Combination of dE/dx and Time-Of-Flight (TOF)

Weak decay topologies

Weak Decay Topologies

V0 Topology (K0s, Λ):

Ξ- (Cascade) Ω- Topology:

Strangeness production in a pion proton event







Strangeness Production in a Pion-Proton Event

Associated production:

Strangeness production in a heavy ion event

Strangeness Production in a Heavy Ion Event

Reconstruction via decay topology

Reconstruction via Decay Topology




Armenteros podolanski plot

Armenteros-Podolanski Plot

Strangeness enhancement sps

Strangeness Enhancement (SPS)

NA57: JPG32, 427 (2006)

Strangeness enhancement rhic

Strangeness Enhancement (RHIC)

STAR: PRC77, 044908 (2008)

Enhancement towards lower energies

Enhancement Towards Lower Energies

√sNN (GeV)

Contrary to naive expectation

Same behavior for multi-strange particles?

Particle ratios in p p rhic and lhc

Particle Ratios in p+p: RHIC and LHC

Increase of relative strangeness production in p+p with √s

ALICE: arXiv:1012.3257

At threshold energies

Ξ at Threshold Energies

Expectation for

statistical model

(Andronic et al.)

HADES: PRL103, 132301 (2009)

Strangeness enhancement as qgp signature

Strangeness Enhancement as QGP Signature ?

Is it a dominantly partonic effect or can hadronic processes lead to the same fast equilibration?

Multi-meson fusion processes

C. Greiner and S. Leupold, J. Phys. G 27, L95 (2001)

Dynamic equilibration at the phase boundary?

P. Braun-Munzinger, J. Stachel, and C. Wetterich, Phys. Lett. B 596, 61 (2004)

Hadronization generally a statistical phenomenon?

U. Heinz, Nucl. Phys. A 638, 357c (1998), R. Stock, Phys. Lett. B 456, 277 (1999)

Energy dependence of k ratios

Energy Dependence of K/π Ratios

Quite sharp maximum in K+/π+ ratio

Indication for phase transition (?)

PRC77, 024903 (2008)


Energy dependence of hyperon ratios



Energy Dependence of Hyperon/π Ratios

|y| < 0.4



 = 1.5 (+ + -)

|y| < 0.5

PRC78, 034918 (2008)

Maximum of relative strangeness production

Maximum of Relative Strangeness Production

Chemical freeze out curve

Chemical Freeze-Out Curve

Chemical freeze out in the qcd phase diagram

Chemical Freeze-Out in the QCD Phase Diagram



Rapidity distributions

Rapidity Distributions ...

BRAHMS: Au+Au, √sNN = 200 GeV


Landau ...

p+p Data

Pion production ~ Entropy

Isentropic expansion

Description of the pion gas as a 3D relativistic fluid


dN/dy is Gaussian of a width given by:

L. D. Landau, Izv. Akad. Nauk. SSSR 17 (1953) 52

P. Carruthers and M. Duong-Van, PRD8 (1973) 859

Landau works also for heavy ions

Landau ... works also for Heavy Ions

BRAHMS: PRL94, 162301 (2005)

Width of the rapidity distribution

Width of the Φ Rapidity Distribution

Expectation for kaon coalescence

K+ + K- → Φ

PRC78, 044907 (2008)

Radial expansion and transverse momentum spectra

Radial Expansion and Transverse Momentum Spectra

1/mT dN/dmT

1/mT dN/dmT



No radial flow:

exponential spectrum

(p+p collisions)

With radial flow:

add. boost by expansion (vT)

⇒ blue shifted spectrum

Blast wave analysis of particle spectra

Blast Wave Analysis of Particle Spectra



158A GeV

E. Schnedermann and U. Heinz,

PRC50, 1675 (1994)

Energy dependence of kinetic freeze out

Energy Dependence of Kinetic Freeze-Out


Energy dependence of m t

Energy Dependence of 〈mT〉

NA49: PRC77, 024903 (2008)

Radial expansion of strange particles

Radial Expansion of Strange Particles

What about heavy particles (Ξ, Ω, J/ψ) ?

NA57: JPG32, 2065 (2006)

Radial expansion of strange particles1

Radial Expansion of Strange Particles

Particles with low hadronic cross sections: Ξ, Ω, J/ψ

⇒ Not sensitive to flow in hadronic, but maybe to partonic phase

N. Xu and M. Kaneta, NPA698, 306 (2002) 306.

Radial expansion of strange particles2

Radial Expansion of Strange Particles

Multi-strange particles sensitive to the partonic flow contribution (?)

STAR: PRL92, 182301 (2004)





Strong decays ⇒ short lifetimes that can be in the

order of the fireball lifetime


K(892) → K+ + π - : cτ = 3.91 fm

Φ(1020) → K+ + K- : cτ = 46.5 fm

Σ-(1385) → Λ + π - : cτ = 5.08 fm

Λ(1520) → p + K- : cτ = 12.7 fm

Should be sensitive to the late phase of the hadronic fireball


Rescattering of decay products

⇒ Provide information on the time span between

chemical and kinetic freeze-out

Recombination and rescattering of resonances

Recombination and Rescattering of Resonances

Picture adapted

from C. Markert

and P. Fachini

Hot and dense


Particle yields







Particle spectra




Measurement of resonances 1385 and 1520

Measurement of Resonances: Σ(1385) and Λ(1520)

STAR: PRC71, 064902 (2005)

Rescattering after chemical freeze out

Rescattering after Chemical Freeze-Out

STAR: PRC71, 064902 (2005)

Comparison to chemical equilibrium expectation

Comparison to Chemical Equilibrium Expectation

Pb+Pb, √sNN = 17.3 GeV

Pb+Pb, √sNN = 17.3 GeV

NA49: pub. in preparation

HGM: F. Becattini et al.

Scaling properties of the meson

Scaling Properties of the Φ Meson

No scaling with K+ × K-

(coalescence picture)

Scaling with (s-Quarks)2

Φ = ss

K+ ∝ s-Quarks

K- + Λ ∝ s-Quarks



K and compared to statistical model

K+/π + and Λ/π – Compared to Statistical Model

A. Andronic et al.,

PLB676, 142 (2009)

Energy dependence of k ratios1

Energy Dependence of K/π Ratios

Quite sharp maximum in K+/π+ ratio

Indication for phase transition (?)

PRC77, 024903 (2008)

Antibaryon baryon ratios

Antibaryon-Baryon Ratios

S = -3

S = -2

S = -1

S = 0

NA49: PRC78, 034918 (2008)

Baryon meson ratios


Baryon meson ratio k 0 s

Baryon-Meson Ratio: Λ/K0s

Λ/K0s > 1: Cannot be understood in string fragmentation picture

Hadronization mechanisms

Hadronization Mechanisms

Fragmentation (Lund model)

String fragments via qq creation

Original parton momentum is

divided among resulting partons


Quark coalescence

Hadrons form by combining quarks

from quark soup (QGP)

Would be dominating at intermediate pt

Fragmentation vs coalescence

Hadron from


ph = zp, z < 1

Hadron from


ph = p1 + p2

Fragmentation vs Coalescence

Production of baryons favored relative to mesons in

coalescence picture

Baryon meson ratio sss ss


Baryon-Meson Ratio: Ω(sss)/Φ(ss)

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