High pt Measurements at the SPS

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High pt Measurements at the SPS
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High pt at the SPS
Chemical freeze-out points approach phase
boundary at top SPS energies
Energy density at ?s 17.3 GeV ?0 ? 3GeV/fm3
Transition to QGP is likely to happen in this
region
Any evidence for medium modifications of high
pt spectra ?
Lattice calculations Fodor and
Katz Bielefeld-Swansea group Hadron gas fits
(?) J. Manninen et al.
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High pt at the SPSSuppression seen at SPS?
Published RAA show now indication for high-pt
suppression
BRAHMS nucl-ex/0602018
WA98 Eur. Phys. J. C23 (2002), 225.
CERES nucl-ex/0407019.
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High pt at the SPSComparison to Theory
RAA for ?0 above calculation including jet
quenching Cronin effect (dNg/dy 200 350)
I. Vitev and M. Gyulassy, Phys. Rev. Lett. 89
(2002), 252301.
Problems Not consistent with RCP of WA98
pp baseline very uncertain (extrapolation
from other energies)
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High pt at the SPSNew look at old data
Update of pion RAA Same central AA data
Reassessment of pp reference ? No
Cronin-enhancement seen
D. DEnterria, Phys. Lett. B 596 (2004), 32.
I. Vitev and M. Gyulassy, PRL 89 (2002), 252301
Consistent with quenching calculation dNg/dy
400-600
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Azimuthal CorrelationsFirst Results from CERES
Azimuthal correlations for PbAu at 158A GeV
Semi-hard two particle correlation on top of flow
component ?
CERES Phys. Rev. Lett. 92 (2004) 032301
Away side peaks broadens with centrality
In-medium parton scattering? Same picture as
at RHIC?
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High pt at the SPSWhat is new at ?s 17.3 GeV?

• RCP for PbPb at 158A GeV up to pt ? 4GeV/c
• NA57 h-, K0s, ?, ?
• NA49 ?, K, p, p
• Azimuthal correlations à la PHENIX
• CERES PbAu 2.5 GeV/c lt
  pttrigger lt 4.0 GeV/c
  1.0 GeV/c lt ptassoc. lt 2.5
  GeV/c
• Ratios of identified particles
• NA49 p/?, p/?-, ?/K0s

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Baseline MeasurementsCronin Effect and Jet
Quenching
Not so really high pt at the SPS (pt ? 4 4.5
GeV/c)
Interplay between Cronin enhancement and
possible jet quenching effects
? Baseline measurements in pp and pA important!
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Baseline MeasurementsCronin Effect in p(d)A Data
Nuclear enhancement factor for min. bias p(d)A
? / ?0
?s 17.3?
Clear energy dependence of enhancement factor
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Baseline MeasurementsEnergy Dependence of Cronin
Effect
RpA increases by factor 5 between RHIC
(200GeV) and ?s 19.4GeV
Even stronger increase towards lower energies
indicated by Serpukhov data! RpA at ?s
17.3GeV? Measurement needed (WA98 pC/Pb)
?s 17.3GeV
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Baseline Measurementspp Data
Shape of pt-spectra in high-pt region
changes around SPS energies
Kinematical effects become important at lower ?s
? Difficult to parametrize
Especially for charged particles, where data are
sparse But More data available for ?0
Data points are scaled!
Only existing pp reference _at_ ?s 17.3GeV pp ?
? X by NA49 pt lt 2.1 GeV/c! Eur. Phys. J.
C45 (2006) 343
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Comparison Central PbPb ? ppRAA _at_ ?s 17.3GeV
Update
RAA 1 up to pt 4.2GeV/c
Consistent with energy loss scenario
(Assumption Blattnig et al. provides proper
pp-baseline!)
NA49 A. Laszlo et al., nucl-ex/0510054
But For final conclusions a pp measurement
up to pt ? 4GeV/c is needed!
Theoretical prediction with energy loss dNg/dy
400-600 Cronin shadowing I. Vitev and M.
Gyulassy, PRL 89 (2002), 252301
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Comparison Central PbPb ? ppRAA Comparison to
RHIC _at_ ?s 22.4GeV
Recent CuCu data _at_ ?s 22.4GeV support RAA ?
1-1.5 above pt 2GeV/c
PHENIX C. Klein-Bösing et al., nucl-ex/0606013
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Central ? Peripheral PbPbNew Data _at_ ?s 17.3GeV
preliminary
NA57 Phys. Lett. B623 (2005), 17
NA49 A. Laszlo et al., nucl-ex/0510054
RCP for ?,K, p
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Central ? Peripheral PbPbComparison to Theory
NA57
NA49 preliminary
Consistent with quenching scenario
Calculations X.N. Wang, PRC68 (2001) 064910,
PRL81 (1998) 2655, PLB595
(2004) 165, priv. com. PQM A. Dainese, C.
Loizides, G. Paic, EPJC38 (2005) 495
Mass Ordering RCP(?,p) gt RCP(K0s,?) Similar as
observed at RHIC
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Central ? Peripheral PbPbPions and h- _at_ ?s
17.3GeV
RCP(h-) gt 1 above pt 3GeV/c Kaon contribution?
RCP(?0, WA98) lt RCP(?, NA49) Note different
centrality ranges
NA57 Phys. Lett. B623 (2005), 17
NA49 A. Laszlo et al., nucl-ex/0510054
WA98 Eur. Phys. J. C23 (2002), 225.
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Central ? Peripheral PbPbKaons _at_ ?s 17.3GeV
K0s(NA57) and K(NA49) agree above pt
1.5GeV/c But discrepancies at lower pt
NA49 A. Laszlo et al., nucl-ex/0510054
NA57 Phys. Lett. B623 (2005), 17
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Central ? Peripheral PbPbProtons and ? _at_ ?s
17.3GeV
Good agreement between RCP(p, NA49) and RCP(?,
NA57)
NA49 A. Laszlo et al., nucl-ex/0510054
NA57 Phys. Lett. B623 (2005), 17
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Central ? Peripheral PbPbComparison SPS to RHIC
NA57 Phys. Lett. B623 (2005), 17
NA49 A. Laszlo et al., nucl-ex/0510054
Clear energy dependence of RCP
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Central ? Peripheral PbPbEnergy Dependence of
RCP for Pions and h-
Strongest drop of RCP between ?s 17.3GeV and
?s 62.4GeV
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Central ? Peripheral PbPbMass Dependence of RCP
Clear mass ordering of RCP observed _at_ ?s
17.3.GeV
RCP(p,?) gt RCP(K) ? RCP(?)
Similar as seen at RHIC (200GeV) and in pA data
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Azimuthal CorrelationsCERES PbAu _at_ ?s 17.3GeV
CERES M. Ploskon et al., nucl-ex/0511043 Details
Talk by M. Ploskon, parallel session II
2.5 GeV/c lt pttrigger lt 4.0 GeV/c 1.0 GeV/c lt
ptassoc. lt 2.5 GeV/c
Flow contribution by ZYAM method
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Azimuthal CorrelationsComparison SPS ? RHIC
CERES
?s 200 GeV
?s 17.3 GeV
2.5 GeV/c lt pttrigger lt 4.0 GeV/c 1.0 GeV/c lt
ptassoc. lt 2.5 GeV/c
PHENIX nucl-ex/0507004
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Azimuthal CorrelationsCentrality Dependence of
Widths
Broad away side structure Broader than pp-like
di-jet expectation (e.g. PHYTIA)
No significant centrality dependence of RMS
CERES
Modification of away side shape seen also at SPS
Effect of partonic interaction with medium?
PHENIX nucl-ex/0507004
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Baryon / Meson Ratios at High-ptCoalescence
Picture
Coalescence models applicable at SPS?
NA57 G. Bruno and A. Dainese, nucl-ex/0511020
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Baryon / Meson Ratios at High-ptComparison to
RHIC
?/K0s
p/?
NA49 T. Schuster et al., nucl-ex/0606005
pt-dependence of baryon/meson ratio appears to be
energy independent
STAR nucl-ex/0601042
PHENIX Phys. Rev. C 69 (2004), 034909
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Baryon / Meson Ratios at High-ptEnergy
Dependence of p/? and p/?-
p/? ratio at pt 3GeV/c increases rapidly
towards lower energies stronger increase than
in pp (A)!
p/?
AA
pA
pp
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Summary

• Baseline measurements
• Solid pp and pA baseline missing!
• pp (NA49) pt lt 2.1GeV/c
• pA Ongoing re-analysis of WA98 data (pt lt
  3-3.5GeV/c)
• Important, since spectral shape strongly ?s
  dependent at SPS
• Evidence for high pt suppression at SPS?
• RAA consistent with jet quenching Cronin (but
  see above)
• Supported by new measurements of RCP (NA57 and
  NA49)
• Suppression relative to pA ? 0.5! (RHIC_at_200GeV
  ? 0.2)
• Azimuthal correlations
• CERES results qualitatively similar to RHIC
• Indications for partonic interaction with medium
• Baryon / meson comparison
• Mass dependence of RCP, large p/?- and
  ?/K0s-ratios
• Test for quark coalescence models

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Thanks!
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Baseline Measurementspp Parametrization
High-pt pion spectra in central PbPb at ?s
17.3GeV
?0-Parametrization by Blattnig et al., as
suggested in D. dEnterria, Phys. Lett. B 596
(2004), 32. QCD-NLL D. de Florian and W.
Vogelsang, Phys. Rev. D 71 (2005), 114004.
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High pt at the SPSKinematical Regime
Bjørken-x region ? 0.1
Anti-shadowing region
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High pt at the SPSNew NA49 data at ?s 17.3 GeV
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Central ? Peripheral PbPbCentrality Dependence
of RCP
No dramatic centrality dependence of RCP
observed
NA57 Phys. Lett. B623 (2005), 17
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Azimuthal CorrelationsFirst Results from CERES
Azimuthal correlations for PbAu at 158A GeV
Semi-hard two particle correlation on top of flow
component ?
CERES Phys. Rev. Lett. 92 (2004) 032301
Away side peaks broadens with centrality
In-medium parton scattering? Same picture as
at RHIC?
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Baryon Meson Ratios at High-ptCoalescence Picture
Baryon/meson ratio increases with pt Similar to
RHIC Coalescence models applicable at SPS?
NA49 A. Laszlo, QM05 T. Schuster
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Comparison Central PbPb ? ppRAA Centrality
Dependence
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Baryon / Meson Ratios at High-ptCentrality
Dependence of p/? and p/?-