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
Flow
Jets +
Heavy Flavor
Photons
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Strangeness
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)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Statistical Models
Multiplicities determined by
statistical weights
(⇒ chemical equilibrium)
A.Andronic et al.
PLB673, 142 (2009)
Grand-canonical partition function:
⇒ Parameters: V, T, μB, γS
F.Becattini et al.,
PRC69, 024905 (2004)
Details: see F. Becattini’s lecture
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Hadronic Transport Models
Microscopic approach
Pb+Pb @ √sNN = 17.3 GeV
UrQMD
Hadronic degrees of freedom
Non-equilibrium
Production mechanisms:
Measured and parameterized
cross sections
String-excitation and fragmentation
Medium effects,
Examples:
Multi-meson fusion,
UrQMD
Mass shifts,
HSD
...
NEXUS
(AMPT)
(EPOS)
...
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Strange Particles
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Major Strangeness Carriers: Kaons and Lambdas
Strangeness Conservation

s
Isospin Symmetry

Isospin Symmetry

K- (us)

s
=
K0 (ds)
K+ (us)
>>

 (uds)
>>
 (uds)

If baryon density is high
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011

K0 (ds)
Measurement of Charged Kaons via dE/dx
Bethe-Bloch function:
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Combination of dE/dx and Time-Of-Flight (TOF)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Weak Decay Topologies
V0 Topology (K0s, Λ):
Ξ- (Cascade) Ω- Topology:
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Strangeness Production in a Pion-Proton Event
p
+
-

-
K0
Associated production:
-
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Strangeness Production in a Heavy Ion Event
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Reconstruction via Decay Topology
NA49
NA57
Christoph Blume
NA57
Villa Gualino, Turino, 7-12 March 2011
Armenteros-Podolanski Plot
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Strangeness Enhancement (SPS)
NA57: JPG32, 427 (2006)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Strangeness Enhancement (RHIC)
STAR: PRC77, 044908 (2008)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Enhancement Towards Lower Energies
√sNN (GeV)
Contrary to naive expectation
Same behavior for multi-strange particles?
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Particle Ratios in p+p: RHIC and LHC
Increase of relative strangeness production in p+p with √s
ALICE: arXiv:1012.3257
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Ξ at Threshold Energies
Expectation for
statistical model
(Andronic et al.)
HADES: PRL103, 132301 (2009)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
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)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Energy Dependence of K/π Ratios
Quite sharp maximum in K+/π+ ratio
Indication for phase transition (?)
PRC77, 024903 (2008)
arXiv:1007.2613
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Energy Dependence of Hyperon/π Ratios
|y| < 0.4
/
-/
|y| < 0.5
−
+/
−
/
 = 1.5 (+ + -)
PRC78, 034918 (2008)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Maximum of Relative Strangeness Production
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Chemical Freeze-Out Curve
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Chemical Freeze-Out in the QCD Phase Diagram
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Spectra
Rapidity Distributions ...
BRAHMS: Au+Au, √sNN = 200 GeV
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Landau ...
p+p Data
Pion production ~ Entropy
Isentropic expansion
Description of the pion gas as a 3D relativistic fluid
Prediction:
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
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Landau ... works also for Heavy Ions
BRAHMS: PRL94, 162301 (2005)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Width of the Φ Rapidity Distribution
Expectation for kaon coalescence
K+ + K- → Φ
PRC78, 044907 (2008)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
1/mT dN/dmT
1/mT dN/dmT
Radial Expansion and Transverse Momentum Spectra
mT
mT
No radial flow:
exponential spectrum
(p+p collisions)
Christoph Blume
With radial flow:
add. boost by expansion (vT)
⇒ blue shifted spectrum
Villa Gualino, Turino, 7-12 March 2011
Blast Wave Analysis of Particle Spectra
Central
Pb+Pb
158A GeV
E. Schnedermann and U. Heinz,
PRC50, 1675 (1994)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Energy Dependence of Kinetic Freeze-Out
arXiv:1007.2613
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Energy Dependence of 〈mT〉
NA49: PRC77, 024903 (2008)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Radial Expansion of Strange Particles
What about heavy particles (Ξ, Ω, J/ψ) ?
NA57: JPG32, 2065 (2006)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
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.
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Radial Expansion of Strange Particles
Multi-strange particles sensitive to the partonic flow contribution (?)
STAR: PRL92, 182301 (2004)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Resonances
Resonances
Strong decays ⇒ short lifetimes that can be in the
order of the fireball lifetime
Examples:
K(892) → K+ + π - :
Φ(1020) → K+ + K- :
cτ = 3.91 fm
cτ = 46.5 fm
Σ-(1385) → Λ + π - :
Λ(1520) → p + K- :
cτ = 5.08 fm
cτ = 12.7 fm
Should be sensitive to the late phase of the hadronic fireball
Regeneration
Rescattering of decay products
⇒ Provide information on the time span between
chemical and kinetic freeze-out
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Recombination and Rescattering of Resonances
Picture adapted
from C. Markert
and P. Fachini
Hot and dense
medium
Particle yields
Particle spectra
K
K
K*
π
K*
K π
π
Time
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Measurement of Resonances: Σ(1385) and Λ(1520)
STAR: PRC71, 064902 (2005)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Rescattering after Chemical Freeze-Out
STAR: PRC71, 064902 (2005)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
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.
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Scaling Properties of the Φ Meson
No scaling with K+ × K(coalescence picture)
2
Scaling
_ with (s-Quarks)
Φ = ss
_
+
K
∝ s-Quarks
K- + Λ ∝ s-Quarks
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
K+/π + and Λ/π – Compared to Statistical Model
A. Andronic et al.,
PLB676, 142 (2009)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Energy Dependence of K/π Ratios
Quite sharp maximum in K+/π+ ratio
Indication for phase transition (?)
PRC77, 024903 (2008)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Antibaryon-Baryon Ratios
S = -3
S = -2
S = -1
S=0
NA49: PRC78, 034918 (2008)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Baryon-Meson-Ratios
Baryon-Meson Ratio: Λ/K0s
Λ/K0s > 1: Cannot be understood in string fragmentation picture
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
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
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
Fragmentation vs Coalescence
Hadron from
fragmentation:
ph = z p, z < 1
Hadron from
coalescence:
ph = p1 + p2
Production of baryons favored relative to mesons in
coalescence picture
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011
_
Baryon-Meson Ratio: Ω(sss)/Φ(ss)
Christoph Blume
Villa Gualino, Turino, 7-12 March 2011