Upload
holly
View
28
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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. - PowerPoint PPT Presentation
Citation preview
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
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Observables
StrangenessStrangeness
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Strangeness in Heavy Ion Physics
Strangeness enhancement as a QGP signatureJ. 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
Multiplicities determined bystatistical weights ( chemical equilibrium)⇒
Grand-canonical partition function:
⇒ Parameters: V, T, μB, γS
Details: see F. Becattini’s lecture
Statistical Models
F.Becattini et al., PRC69, 024905 (2004)
A.Andronic et al. PLB673, 142 (2009)
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Hadronic Transport Models
Examples:UrQMD
HSD
NEXUS
(AMPT)
(EPOS)
...
Microscopic approachHadronic degrees of freedom
Non-equilibrium
Production mechanisms:Measured and parameterized
cross sections
String-excitation and fragmentation
Medium effects,
Multi-meson fusion,
Mass shifts,
...
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
ss ss
Strangeness Conservation==
Isospin Symmetry
K0 (ds)K0 (ds)K+ (us)K+ (us)
Isospin Symmetry
K- (us)K- (us) K0 (ds)K0 (ds)
(uds) (uds) (uds) (uds)
>>
>>
If baryon density is high
>>>>
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
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
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
NA57NA57
NA49
Christoph Blume 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
ALICE: arXiv:1012.3257
Increase of relative strangeness production in p+p with √s
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Ξ at Threshold Energies
HADES: PRL103, 132301 (2009)
Expectation for statistical model(Andronic et al.)
Expectation for statistical model(Andronic et al.)
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Is it a dominantly partonic effect or can hadronic processes lead to the same fast equilibration?
Multi-meson fusion processesC. 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)
Strangeness Enhancement as QGP Signature ?
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
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
SpectraSpectra
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Rapidity Distributions ...
BRAHMS: Au+Au, √sNN = 200 GeV
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Landau ...
Prediction: dN/dy is Gaussian of a width given by:
L. D. Landau, Izv. Akad. Nauk. SSSR 17 (1953) 52P. Carruthers and M. Duong-Van, PRD8 (1973) 859
Pion production ~ Entropy Isentropic expansionDescription of the pion gas as a 3D relativistic fluid
p+p Data
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 coalescenceK+ + K- → Φ
PRC78, 044907 (2008)
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Radial Expansion and Transverse Momentum Spectra
mT
1/m
T d
N/d
mT
mT
1/m
T d
N/d
mT
No radial flow:exponential spectrum(p+p collisions)
With radial flow:add. boost by expansion (vT)
⇒ blue shifted spectrum
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Blast Wave Analysis of Particle Spectra
Central Pb+Pb158A 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
N. Xu and M. Kaneta, NPA698, 306 (2002) 306.
Particles with low hadronic cross sections: Ξ, Ω, J/ψ
⇒ Not sensitive to flow in hadronic, but maybe to partonic phase
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Radial Expansion of Strange Particles
STAR: PRL92, 182301 (2004)
Multi-strange particles sensitive to the partonic flow contribution (?)
ResonancesResonances
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Strong decays short lifetimes that can be in the ⇒ order of the fireball lifetime
Examples:K(892) → K+ + π - : cτ = 3.91 fmΦ(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 fireballRegenerationRescattering of decay products
⇒ Provide information on the time span between chemical and kinetic freeze-out
Resonances
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Recombination and Rescattering of Resonances
Hot and dense medium
Particle yields
Particle spectra
Time
K*πK πK
K*
K
π
Picture adapted from C. Markert and P. Fachini
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
NA49: pub. in preparation
HGM: F. Becattini et al.
Pb+Pb, √sNN = 17.3 GeVPb+Pb, √sNN = 17.3 GeV
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
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∝
_
_
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
NA49: PRC78, 034918 (2008)
S = -3
S = -2
S = -1
S = 0
Baryon-Meson-RatiosBaryon-Meson-Ratios
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
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 quarksfrom quark soup (QGP)
Would be dominating at intermediate pt
Christoph Blume Villa Gualino, Turino, 7-12 March 2011
Fragmentation vs Coalescence
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)_