Strangeness Production in Heavy Ion Collisions at SPS Energies

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Strangeness Productionin Heavy Ion Collisions
at SPS Energies
André Mischke for the NA49 Collaboration
a.mischke_at_phys.uu.nl
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Outline

• Physics Programme
• Experimental Setup
• Particle Identification / V0-Reconstruction
• Spectra on Kaons, ? and ?
• Energy Dependence
• Baryon Ratios
• Summary

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Physics Programme in NA49

• Search for the onset of deconfinement
• Energy scan programme at CERN-SPS (started in
  99)
• - central Pb-Pb events at 20, 30, 40, 80 and 158
  AGeV
• Search for anomalies in the energy dependence
• of physical observables here strangeness
  production
• - s quarks are mainly carried by the ?
• - essentially half of the?s quarks are contained
  in K

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NA49 Detector at CERN-SPS

• 2 super-conducting dipole magnets,
• 9 Tm bending power
• 4 volume TPCs for tracking and
• PID via dE/dx
• 2 ToF walls for PID at mid-rapidity
• 180,000 channels
• Event rate 7 Hz

• Fixed target experiment
• Large acceptance hadron
• spectrometer

NIM A430, 210 (1999)
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Identification of Charged Particles

• Specific energy loss dE/dx
• cover forward rapidity
• (p gt 7 GeV/c)
• dE/dx resolution 4

• Time-of-Flight
• at mid-rapidity
• resolution 60ps

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V0 - Reconstruction
Neutral strange particles are identified by
their decay topology ? ? p ?- (64.1 ) For
the spectra ? contain ?0
158 AGeV
Invariant mass spectra - measured mass
in agreement with PDG -
mass resolution ??? 2 MeV/c2
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Kaons Transverse Spectra
at mid-rapidity
Slopes are similar for K and K-
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Kaons Rapidity Distributions
K broader than K-
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Energy Dependence of K/? ratio
published
RHIC
Pronounced maximum
Kink-like structure
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? Transverse Spectra
at mid-rapidity
Slope parameter slightly increases with
increasing energy
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? Rapidity Distributions

• ? broader than??
• Flattening of the ? rapidity distribution

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Energy Dependence of ?/? ratio
nucl-ex/0209002
Non-monotonic energy dependence
Continuous rise
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Strangeness Enhancement in ? Production
?N ? ?K dominant process
hep-ph/0209284

• Same behaviour for the K/? ratio
• Strangeness enhancement not a unique
• signature for QGP formation

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Spectra on ?
Slope increases with energy
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? Energy Dependence
PLB 491, 59 (2000)
NA49 Preliminary
?/? increases monotonically
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Multi-strange Baryons
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Effect of Baryon Density

• Strong increase with energy
• due to decreasing baryon density
• Particle ratios increase with the number
• of valence s/sbar quarks in the baryon

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Summary

• Large data sets available for the SPS energy
  range from
• 20 to 158 GeV per nucleon
• Excitation function of K and ? production in HIC
• - Pronounced maximum in the K/? ratio around
  30 AGeV
• - ?/? ratio shows a maximum at the same energy
• ?/? ratio increases monotonically with cms energy
  
• First results on multi-strange hyperons at lower
  SPS energies

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Collaboration
20 Institutes from 12 nations 96 participants
T. Anticic, B. Baatar, D. Barna, J. Bartke, M.
Behler, L. Betev, H. Bialkowska, A. Billmeier,
C. Blume, B. Boimska, M. Botje, J. Bracinik, F.P.
Brady, R. Bramm, R. Brun, P. Buncic, V. Cerny,
P. Christakoglou, J.G. Cramer, P. Csato, P.
Dinkelacker, V. Eckardt, F. Eckhardt, P. Filip,
H.G. Fischer, Z. Fodor, P. Foka, P. Freund, V.
Friese, J. Gal, M. Gazdzicki, G. Georgopoulos,
E. Gladysz, S. Hegyi, C. Höhne, K. Kadija, A.
Karev, V.I. Kolesnikov, T. Kollegger, R. Korus,
M. Kowalski, I. Kraus, M. Kreps, M. van Leeuwen,
B. Lasiuk, M. van Leeuwen, P. Levai, A.I.
Malakhov, C. Markert, B.W. Mayes, G.L. Melkumov,
C. Meurer, A. Mischke, M. Mitrovski, J. Molnar,
St. Mrowczynski, G. Palla, A.D. Panagiotou, K.
Perl, A. Petridis, M. Pikna, L. Pinsky, F.
Pühlhofer, J.G. Reid, R. Renfordt, W. Retyk, C.
Roland, G. Roland, M. Rybczynski, A. Rybicki, A.
Sandoval, H. Sann, N. Schmitz, P. Seyboth, F.
Sikler, B. Sitar, E. Skrzypcak, G. Stefanek, R.
Stock, H. Ströbele, T. Susa, I. Szentpetery, J.
Sziklai, T.A. Trainor, D. Varga, M. Vassiliou,
G.I. Veres, G. Vesztergombi, D. Vranic , S.
Wenig, A. Wetzler, Z. Wlodarczyk, I.K. Yoo, J.
Zaranek, J. Zimanyi
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Add. Slide(s)
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Energy Dependence of Pion Production