quark matter 2006 november 18, 2006
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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
Ncoll,Pb+Pb = 78 ± 12
p+C A+AAA
A+A T p+C
d / d
d / dT
T N pR
T N p= ×
inelA+A coll NNA+A
/T N s=
inelp+C coll NNp+C
/T N s=
Ncoll,Pb+Pb = 207 ± 21 Ncoll,Pb+Pb = 408 ± 41 Ncoll,Pb+Pb = 569 ± 57 Ncoll,Pb+Pb = 712 ± 71 Ncoll,Pb+Pb = 807 ± 81 preliminary
0 RAA ~ 0.4 in 1% most central Pb+Pb collisions (p+C reference)
14 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
RAA in Pb+Pb with p+Pb Reference:Centrality Dependence
p+Pb A+AAA
A+A T p+Pb
d / d
d / dT
T N pR
T N p= ×
inelA+A coll NNA+A
/T N s=
inelp+Pb coll NNp+Pb
/T N s=
Ncoll,Pb+Pb = 78 ± 12 Ncoll,Pb+Pb = 207 ± 21 Ncoll,Pb+Pb = 408 ± 41 Ncoll,Pb+Pb = 569 ± 57 Ncoll,Pb+Pb = 712 ± 71 Ncoll,Pb+Pb = 807 ± 81
0 RAA ~ 0.4 in 1% most central Pb+Pb collisions (p+Pb reference)
preliminary
15 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
0 Suppression in Central Pb+Pb
0 in Pb+Pb at sNN = 17.3 GeV
preliminary
0 suppression in Pb+Pb at sNN = 17.3 GeV for Npart > ~300
16 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Summary
0’s from sNN = 17.3 GeV p+C and p+Pb used as reference for RAA
0 suppression at high pT in central Pb+Pb
Looking forward to extraction of dN/dygluon
1% most central:Ncoll,Pb+Pb = 807 ± 81
preliminary
17 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Backup slides
18 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Comparison to other RpA’s
19 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Comparison to WA80
20 Klaus Reygers, Quark Matter 2006
Westfälische Wilhelms-UniversitätMünster
Cronin Enhancement in p+A at sNN = 17.3 GeV
Cronin Enhancement:
Up to a factor 2 for A 200
Large differences between models!
pT (GeV/c)
Rp
+A
Models calculations for p+A at sNN = 17.3 GeV:
Barnaföldi et al., nucl-th/0307062
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