Westfälische Wilhelms-Universität Münster Hadron Suppression and Nuclear k T Enhancement Studied with Neutral Pions from p+C, p+Pb, and Pb+Pb Collisions at s NN = 17.3 GeV Quark Matter 2006 November 18, 2006 Klaus Reygers University of Münster Germany for the WA98 collaboration
Quark Matter 2006 November 18, 2006 Klaus Reygers University of Münster Germany for the WA98 collaboration. Hadron Suppression and Nuclear k T Enhancement Studied with Neutral Pions from p+C, p+Pb, and Pb+Pb Collisions at s NN = 17.3 GeV. The question is …. - PowerPoint PPT Presentation
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Westfälische Wilhelms-UniversitätMünster
Hadron Suppression and Nuclear kT
Enhancement Studied with Neutral Pions from p+C, p+Pb, and Pb+Pb Collisions
at sNN = 17.3 GeV
Quark Matter 2006 November 18, 2006
Klaus ReygersUniversity of Münster
Germanyfor the WA98 collaboration
2 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
The question is …
Strong evidence for QGP formation
Characterization of the medium(dNgluon/dy 1500)
High-pT-hadron suppression at RHIC
What can we say at CERN SPS energies?
3 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Is there Jet Quenching at sNN = 17.3 GeV?We don’t know!
A+AAA
AA T p+p
d / d
d / dTN p
RT ps
=´
No measured p+p reference at same energy
Nuclear kT enhancement not well understood at sNN ~ 17 GeV
Parameterizationfrom Blattnig et al:Large uncertainty!
Blattnig et al.,Phys. Rev. D 62 (2000) 094030
D. d’Enterria, Phys. Lett. B 596 (2004), 32
p+W @ s = 19.4GeV
Parton energy lossdNgluon/dy = 400 – 600
C. Blume, nucl-ex/0609022
4 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Cronin Enhancement at sNN = 17.3 GeV
Cronin enhancement:
Slightly larger in A+A than in p+A
Strongly model dependent: Maximum enhancement factors between ~2 and ~4
Calculation without parton energy loss:
I. Vitev, M. Gyulassy, PRL 89, 252301,2002
Cronin + shadowing
Expect to take out effect of Cronin enhancement on RAA to large extent with p+Pb reference
Barnaföldi et al., nucl-th/0307062
X.N. Wang, PRC 61, 064910, 2000
I. Vitev, M. Gyulassy
sNN = 17 GeV
5 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Idea of this Analysis:p+C and p+Pb as Reference for Pb+Pb RAA
Reaction System Year
Pb+Pb at sNN = 17.3 GeV 1994, 1995, 1996
p+C, p+Pb at sNN = 17.3 GeV 1996
0 spectra published:
Presented in this talk
p + C: → Replacement for p+p reference(Ncoll 1.7 expect small Cronin enhancement)
p + Pb: → Study nuclear kT enhancement by comparing to p+C
→ Reference for RAA in Pb+Pb: partially removes effect
of Cronin enhancement
Eur.Phys.J.C23:225-236,2002
6 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
WA98 Experiment
Minimum bias trigger
High Energy Photon Trigger(pT, > ~ 0.7 GeV/c)
0p
3.5 < < 5.5
2.1 < < 3.0
7 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Calibration and Peak Extraction
Same calibration as in Pb+Pb run
Confirmed with comparison to GEANT simulation
0 peak position in GEANT simulation
p+C p+C
0 peak width in GEANT simulation
8 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Spectra in p+C and p+Pb
Transition to high-pT photon sample at pT = 1.4 GeV/c
Similar pT reach as in Pb+Pb
0 in sNN = 17.3 GeV p+A
preliminary
9 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Cross Check: Comparison to NA49
NA49, hep-ex/0606028
Ratio: WA98 / NA49
sNN = 17.3 GeV p+C
Good agreement with charged pions from NA49
preliminary
10 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
RpPb with p+C Reference
RpPb consistent with 1 at high pT
Hint of Cronin enhancement
coll p+C p+PbpPb
coll Tp+Pb p+C
d / d
d / d
TN N pR
N N p= ×
coll p+C1.7 0.2N = ±
coll p+Pb4.1 0.4N = ±
Effect of minimum biastrigger threshold taken into account
preliminary
p+C reference
11 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
p+C as p+p Reference
No indication of Cronin enhancement in p+C from comparison to NA49 p+p
Agreement with Blattnig parameterization within errors
p+CpC
coll Tp+C p+p
d / d
d / d
TN pR
N N p=
´
preliminary preliminary
NA49, Eur. Phys. J. C 45, 343 (2006)
12 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
RAA in central Pb+Pb at sNN = 17.3 GeV
preliminaryp+C reference
preliminary
p+B A+AAA
A+A T p+B
d / d
d / dT
T N pR
T N p= ×
Proton-nucleus reference measured at same energy:
nuclear overlap function
0-12.7% most central Pb+Pb
p+Pb reference
0-12.7% most central Pb+Pb
0 suppression with respect to p+Pb reference in central Pb+Pb (RAA ~ 0.7 for 0 − 12.7%)
inelX+Y coll NNX+Y
/T N s=
13 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
RAA in Pb+Pb with p+C Reference:Centrality Dependence