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Strangeness from 20 to 158 AGeV

Strangeness from 20 to 158 AGeV. V. Friese Gesellschaft f ür Schwerionenforschung Darmstadt, Germany v.friese@gsi.de. for the collaboration. Outline. NA49 results on particle spectra and yields at SPS energies (30 – 158 AGeV) :. Kaon and pion spectra at 30 AGeV

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Strangeness from 20 to 158 AGeV

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  1. Strangenessfrom 20 to 158 AGeV V. Friese Gesellschaft für Schwerionenforschung Darmstadt, Germany v.friese@gsi.de for the collaboration

  2. Outline NA49 results on particle spectra and yields at SPS energies (30 – 158 AGeV) : • Kaon and pion spectra at 30 AGeV • Energy Dependence of K/ ratio •  spectra at 40 and 80 AGeV • Energy dependence of  yield and slope parameter •  at 158 AGeV: Dielectron channel • Outlook on  in 40 AGeV and  in 30 and 40 AGeV • Particle yields : Chemical freeze-out • Transverse spectra : Kinetic freeze-out 2 SQM03 Atlantic Beach V. Friese, March 2003

  3. Experimental Setup Large acceptance hadron spectrometer Tracking and dE/dx PID in TPCs TOF for PID at mid-rapidity Magnetic field scaled with beam energy 3 SQM03 Atlantic Beach V. Friese, March 2003

  4. p < 2.5 GeV : TOF at midrapidity 2,5 < p < 10 GeV : TOF + dE/dx at midrapidity p > 7 GeV dE/dx forward rapidity Particle ID in NA49 TOF resolution : ~ 60 ps dE/dx resolution : ~ 4 % for resonances : + invariant mass for weak decays : + topology 4 SQM03 Atlantic Beach V. Friese, March 2003

  5. The NA49 Energy Scan Program Central Pb+Pb Data Taking : 5 SQM03 Atlantic Beach V. Friese, March 2003

  6. 20 AGeV : not yet analysed The NA49 Energy Scan Program Central Pb+Pb Data Analysis of Single Particle Spectra & Yields : • : Phys. Lett. B491 (2000) 59 • : Phys. Lett. B538 (2002) 275 K, : Phys. Rev. C66 (2002) 054902 6 SQM03 Atlantic Beach V. Friese, March 2003

  7. ? ? ? Monotonic rise in K-/- Maximum in K+/+ between AGS and low SPS energies Sharp maximum in ES predicted by Stat. Model of the Early Stage Energy Dependence of Kaon Production Status at QM2002 : 7 SQM03 Atlantic Beach V. Friese, March 2003

  8. Kaons at 30 AGeV : Transverse Spectra at mid-rapidity 8 SQM03 Atlantic Beach V. Friese, March 2003

  9. Energy Dependence : Kaon Slope Parameters No dependence of kaon slope parameters on energy at SPS Modification of EOS in phase transition region ? see hep-ph/0303041 9 SQM03 Atlantic Beach V. Friese, March 2003

  10. p r e l i m i n a r y Kaons at 30 AGeV : Rapidity Distributions No increase in midrapidity kaon yield from 30 to 40 AGeV 10 SQM03 Atlantic Beach V. Friese, March 2003

  11. Energy Dependence : Mid-Rapidity K-/K+ 30 GeV point follows smooth evolution from AGS over SPS to RHIC 11 SQM03 Atlantic Beach V. Friese, March 2003

  12. K-/- : in 30 AGeV similar to 40 AGeV K+/+ : significant increase from 40 to 30 AGeV Energy Dependence : Mid-Rapidity K/ 12 SQM03 Atlantic Beach V. Friese, March 2003

  13. Indication for kink structure also for K-/- ? Sharp maximum for K+/+ ! Energy Dependence : Total K/ Ratios 13 SQM03 Atlantic Beach V. Friese, March 2003

  14. where  not published : Energy Dependence : Strangeness to Entropy Data at 30 AGeV support phase transition scenario (Statistical Model of the Early Stage) 14 SQM03 Atlantic Beach V. Friese, March 2003

  15. = ss : more sensitive to strangeness • enhancement than kaons ? n.b. : small deviation from PDG mass seen at all three Pb+Pb data sets, but not in pp.  at 40 and 80 AGeV 15 SQM03 Atlantic Beach V. Friese, March 2003

  16. NA49 preliminary NA49 preliminary  : Transverse Spectra Inverse slope increases with energy In contrast to K+ and K-, but similar to  16 SQM03 Atlantic Beach V. Friese, March 2003

  17. 40 AGeV 80 AGeV 158 AGeV p r e l i m i n a r y statistical errors only  : Rapidity Distributions Rapidity width increases with energy similar to kaons and pions 17 SQM03 Atlantic Beach V. Friese, March 2003

  18. Monotonic increase in  /   / K- constant with beam energy up to RHIC Energy Dependence :  Yields 18 SQM03 Atlantic Beach V. Friese, March 2003

  19.  at 158 AGeV : The Puzzle Strong differences in slope and yield between hadronic channel (NA49) and dimuon channel (NA50) Rescattering of kaons in microscopic models accounts for ~30 % in total yield and ~ 20 MeV in slope only Measurement of   e+e- in NA49 19 SQM03 Atlantic Beach V. Friese, March 2003

  20. background subtracted e+e- inv. mass spectrum  at 158 AGeV : The Dielectron Channel   e+e- 158 AGeV Pb+Pb 20 % central 3 M events No  signal observed Upper limit estimate : <> <~ 40 20 SQM03 Atlantic Beach V. Friese, March 2003

  21. Cascades at 40 AGeV - and + seen and analysed in 40 AGeV (central + minimum bias) see Talk by C. Meurer today 15:10 par. session # 1 21 SQM03 Atlantic Beach V. Friese, March 2003

  22. Signals now observed in 30 and 40 AGeV : 40 AGeV  at 30 and 40 AGeV First rapidity distribution of  in Pb+Pb at 158 AGeV measured by NA49 (see QM2002) see talk by M. Mitrovski Friday 15:10 22 SQM03 Atlantic Beach V. Friese, March 2003

  23. courtesy of F. Beccatini Particle yields at all three energies can be fitted by the Hadron Gas Model with partial strangeness saturation Particle Yields at 40 and 80 AGeV 23 SQM03 Atlantic Beach V. Friese, March 2003

  24. cross-over : Fodor / Katz, hep-lat 0204029 C.R. Allton et.al., hep-lat 0204010 Energy Dependence : Chemical Freeze-Out Chemical freeze-out occurs on a smooth curve in T-B At SPS : close to phase boundary 24 SQM03 Atlantic Beach V. Friese, March 2003

  25. 158 AGeV pions and deuterons not included in fit Kinetic Freeze-Out : mid-rapidity mt spectra radial flow fit (blast wave) also describes heavy hyperons common freeze-out behaviour for all measured particles 25 SQM03 Atlantic Beach V. Friese, March 2003

  26. 40 AGeV Kinetic Freeze-Out at 40 AGeV good description also at 40 AGeV and 80 AGeV (not shown) Parameters T and T similar for all three energies 26 SQM03 Atlantic Beach V. Friese, March 2003

  27. Study in addition strangeness production in light ion collisions see Talk by I. Kraus ,  in C+C and Si+Si Sunday 17:00 par. session #4 The NA49 program on system size dependence Enhancement in strange particle production observed in Pb+Pb compared to pp collisions Can this be observed already in smaller systems (Onset) ? Study strange particle production in peripheral Pb+Pb but : peripheral Pb+Pb has different geometry than central collisions of light nuclei at same Npart Data sets available : Pb+Pb, 158 AGeV, min. bias. Pb+Pb, 40 AGeV, min bias C+C, Si+Si, 158 AGeV 27 SQM03 Atlantic Beach V. Friese, March 2003

  28. Summary • New data from NA49 on kaon production in Pb+Pb at 30 AGeV: • K+/+ shows a sharp maximum around 30 AGeV • K-/ - similar to 40 AGeV • Kaon inverse slope parameters stay constant at SPS energies • Data support the phase transition scenario of SMES •  production in 40 and 80 AGeV:  /  increases monotonically with beam energy  inverse slope parameters also increase from AGS over SPS to RHIC Disagreement of yields in hadronic and muonic channels at 158 AGeV still unresolved No signal seen by NA49 in the dielectron channel • First results on cascades and  at lower SPS energies • Analysis of light systems is ongoing 28 SQM03 Atlantic Beach V. Friese, March 2003

  29. Data taking for energy scan completed • K/ excitation function will be completed with 20 AGeV data •  and  in 20 and 30 AGeV to be analysed • Spectra and yields for cascades at 20, 30 and 80 AGeV • / ratios at 20 (?), 30, 40 and 80 (?) AGeV • Analysis of K* at all available beam energies • System size dependence of strangeness production to be finalised Outlook 29 SQM03 Atlantic Beach V. Friese, March 2003

  30. Energy Dependence of Pion Multiplicity 30 SQM03 Atlantic Beach V. Friese, March 2003

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