Title: Transport Model Analysis of UltraRelativistic AA interactions
1Transport Model Analysis of Ultra-Relativistic
AA interactions
- Marcus Bleicher
- Institut für Theoretische Physik
- Goethe Universität Frankfurt
- Germany
2Thanks to
- Elena Bratkovskaya
- Sascha Vogel
- Xianglei Zhu
- Stephane Haussler
- Hannah Petersen
- Diana Schumacher
3Contents
- Introduction
- Strangeness as QGP signal
- Experimental facts the horn
- Strange fluctuations
- Summary
4The tool UrQMDv2.2
- Non-equilibrium transport model
- Hadrons and resonances
- String excitation and fragmentation
- Cross sections are parameterized
- via AQM or calculated by detailed balance
- pQCD hard scattering at high energies (not in
v1.3) - Generates full space-time dynamics of hadrons
and strings
5Collision Spectrum
1fm/c
10fm/c
- Initial stage scattering before 1.5 fm/c
Baryon stopping, meson production, - Thermalization stage (1.5 6 fm/c) Cooking
QCD matter, may be QGP formation - Hadronic freeze-out stage (6 10 fm/c)
Elastic and pseudo-elastic hadron scatterings
PbPb _at_ 160 AGeV
6Where do we expect QGP?
- 1st Order phase transition at high
- No P.T. at low
- Search for irregularities around Ebeam 10-40
GeV - Flow, strangeness, E-by-E
Plot adapted from L. Bravina
7Strangeness enhancement
T0.2-0.3 GeV
? QGP has lower threshold for strangeness
production ? relative strangeness enhancement
8PP Excitation functions
- PP works nicely
- Perturbative QCD is used for hard scatterings
above 50 GeV
9AA Excitation functions
- 4 and mid-y abundancies OK
- Energy dependence OK
- Hadron-string models work well
10Excitation functions ratios
- Horn in the ratio not reproduced
- well reproduced
- relative strange baryon
enhancement reproduced
11Fluctuation studies Ratios
Taken from Christoph Roland
NA49 Preliminary
NA49 Preliminary
- K/p fluctuations increase towards lower beam
energy - Significant enhancement over hadronic cascade
model - p/p fluctuations are negative
- indicates a strong contribution from resonance
decays
12Baryon-Strangeness Correlations I
Definition
Idea Strangeness and baryon numbercarriers are
different in QGP and hadron gas.
First suggested by V. Koch et al., 2005
- HG strangeness is decoupled from baryon number
(mesons) ? small CBS correlation - QGP strangeness is fixed to baryon number
(strange quark)? large CBS correlation
13Baryon-Strangeness Correlations 2
- Limiting cases for CBS
- Large mB CBS ?3/2
- large acc. window CBS ?0Explored with help
of increasing rapidity window inAuAu reaction
at RHIC
- Present models yield similar results for small
rapidity window - Different handling of the fragmentation
region/spectators influences results at large
rapidities
14Baryon-Strangeness Correlations 3
Energy dependence of CBS allows to study the
onset of deconfinement transition Note that the
QGP result is for m0 Here ymaxlt0.5
- Deviations from the HG are expected around high
SPS energy region, due to QGP onset.
15Baryon-Strangeness Correlations 4
Centrality dependence of CBS allows to study the
critical volume needed for QGP formation. Note
that the QGP result is for m0 ymaxlt0.5,
Ecm200AGeV
- Hadron-string transport models predict no
centrality dependence of CBS - A QGP transition leads to a strong centrality
dependence
16Summary
- Hadron yields are well reproduced in models
- Most ratios can be understood in transport
models - Model K/p ratios do not reproduce the strong
peak observed in data - In data, the dynamical fluctuation of K/p
increase strongly towards 20 AGeV beam energy
(not present in hadron-string models) - Baryon-strangeness correlations allow to pin
down the onset of the QGP transition.
17Conclusion
Most interesting energy range, because
- K/p ratio enhanced
- Large dynamical fluctuations
- Latent heat is big
Will be explored by new GSI accelerator (near
Frankfurt)