Indications of the Onset of Deconfinement at low SPS Energies Recent Results from NA49 ICPAQGP5, Col

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Indications of the Onset of Deconfinementat low
SPS EnergiesRecent Results from
NA49ICPAQGP5, Colcatta, February 2005
V. Friese v.friese_at_gsi.de
for the collaboration
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The NA49 Detector

• Hadron spectrometer
• Large acceptance 4p yields
• PID by dE/dx and TOF
• Centrality by forward calorimeter

Beam energies 20, 30, 40, 80, 158 AGeV Systems
pp, pA, CC, SiSi, PbPb
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Midrapidity mt spectra (central PbPb)
Simultaneous blast wave fit constant ßt p, d
excluded from fit SSH, PRC 48 (1993) 2462
Single fireball model with common temperature and
flow velocity works
Beware Resonance feeddown, velocity profile
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Early freeze out of O ?
Linear velocity profileO agrees better with
charmonia than with other hadrons Indication
for earlier freeze out?
NA49, nucl-ex/0409004
() Gorenstein, Bugaev, Gadzicki, PRL 88 (2002)
132301
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Transverse spectra at lower energies
30 AGeV
20 AGeV
Blast wave fits work at all SPS energies Kinetic
freeze out T 120 130 MeV ßt 0.4 0.5 for
constant ßt
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Kaon Slope Parameters
Kaon spectra almost perfect exponential ? fit
dn/dmt mt e-mt/T
Constant inverse slope at all SPS
energies Constant temperature and pressure? Mixed
phase?
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Average mt
Other particle types No exponential spectrum ?
calculate mean mt
Similar behaviour seen for pions protons less
conclusive
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Longitudinal Distributions (central PbPb)
Gaussianlike rapidity spectra (except p, ?)
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Strange to Nonstrange Ratios Kaons
Sharp structure in K / p, not reproduced by
hadronic models (Full equlibrium) hadron gas
model overpredicts kaons at higher SPS energies
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Strange to Nonstrange Ratios ?
Similar structure seen as in K(sharp peak at 30
AGeV) HGM describes overall structure, but
location of peak different (?) UrQMD not far off
(not shown)
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Total Strangeness
Peak at 30 AGeV,undersaturation at higher SPS
energies
Energy dependence changes at 30 AGeV
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Ruling out hadronic equlibirium ?

• Features of HGM
• No sharp peak
• Overprediction of strangeness yields
  at higher SPS energies
• Maxima at different positions for K, ?, ?, O

If connected with PT, maxima should be at the
same energy for all strange species
? at 20, 30 AGeV possibly discriminative ? to come
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one more Parameter
Becattini et al., PRC 69 (2004) 024905
Introducing ?S lt 1 gives better description of
NA49 4p yieldsaround 30 AGeV ?S 1 At higher
energies ?S 0.7what does it mean?
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Indication for deconfinement PT ?
Gazdzicki, Gorenstein, Act. Phys. Polon. B 30
(1999) 2705
Hama et al., Braz. J. Phys. 34 (2004) 322
Phase transition at 30 AGeV
QGP hadronic phases
Features in strangeness / pion and kaon slopes
can be obtained with models assuming a phase
transition
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Relative Strangeness Fluctuations
Dynamical fluctuations in K/p increase towards
low SPS energies Not reproduced in UrQMD p/p in
agreement with hadronic transport (resonance
decays)
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Mean pt Fluctuations
Measured at top SPS as function of system
size Maximum at small Npart ( 100 ) But
similar pattern observed at RHIC Interesting
Measure at lower SPS energies (hint taken)
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System Size Strangeness Enhancement
NA49, 158 AGeV
Tounsi, Redlich, JPG 28 (2002) 2095
Strangeness enhancement ? canonical
suppression Volume effect on strangeness
conservation
But No quantitative agreement with data (rise
too fast) if V Npart
Disagreement between peripheral PbPb and central
SiSi, CC
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Cluster Ansatz bei C. Höhne
Microscopic calculation of overlapping strings
(VENUS, UrQMD) ? correlation volume as fct. of
Npart Calculate ES ? according to statistical
model, taking into account the distribution in
Vcorr
Describes data perfectly ! Application to
fluctuations?
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Summary

• Anomalies at lower SPS energies observed by NA49
• sharp peak in strange particles to pion ratio
• constancy of kaon slopes
• pion production rate increases (not discussed)
• Fluctuation in K/p also increase towards low SPS
  energies, other signals less convincing / absent
• Best explanation by scenario with onset of
  deconfinement
• Low SPS is still interesting
• EoI to CERN for SPS running from 2009 on
• Plans of fixed target experiments at RHIC
• FAIR at GSI