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SQM 2007 International Conference on Strangeness in Quark Matter

SQM 2007 International Conference on Strangeness in Quark Matter. Strangeness Production at SIS Energies. Xavier Lopez x.lopez@gsi.de. Strangeness Production at SIS Energies. Introduction The FOPI Detector Strange resonances in medium Search of strange

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SQM 2007 International Conference on Strangeness in Quark Matter

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  1. SQM 2007International Conference on Strangeness in Quark Matter Strangeness Production at SIS Energies Xavier Lopez x.lopez@gsi.de

  2. Strangeness Production at SIS Energies • Introduction • The FOPI Detector • Strange resonances • in medium • Search of strange • multi-baryonic states • Conclusions / Outlook

  3. The physics of strangeness at SIS (2 AGeV) SIS • In medium effects could be induced • by a partial chiral symmetry restoration • Decreasing part of quarks condensate • Beam energy close or below the production • threshold of strange particles • High baryonic densities (2-3 ρ0) reached • during a relatively long time (~ 10 fm/c) W. Weise, Prog. Theor. Phys. Suppl. 149 (2003) 1 B. Friman et al., EJPA 3 (1998) 165

  4. C. Hartnack nucl-th/0507002 Strangeness at SIS: Production mechanisms • K+ and Y essentially produced via secondary • reactions:Δ + N → K+,0 + Y + B • K+,0 produced during the earlier stage of the • collision (high densities) • - repulsive potential (KN ~ 20-30 MeV from diff. v1) • Complex K- production mechanism • - strangeness exchange reactions: • π + Y ↔ K- + B • - strong attractive potential • (~ 70 MeV at ρ = ρ0) • - coupled in the medium with • Σ(1385), Λ(1405) and Λ(1520) M.F. M. Lutz et al., NPA 700 (2002) 309

  5. Akaishi and Yamazaki: K-N bound-state of -27 MeV • prediction of the existence of K-pp state • K-pp → p + Λ + 263 MeV • B = 48 MeV, Γ = 60 MeV • Measurement: FINUDA peak at 2.25 GeV • and Γ = 67 MeV (Bmodel = 115 MeV) • Weise and Doté: absorption • KN→ πΛ, πΣKNN→ ΛN, ΣN • K-NN state of Γ = 100 MeV, B = 60 MeV • Magas and Oset: final state interaction • Therm. model: abondance of kaonic • clusters ~ strange resonances yields at SIS K-N potential: prediction of bound states K- stopped in 7Li T. Yamazaki and Y. Akaishi nucl-exp/0609041 M. Agnello et al., PRL 94, (2005) 212303 A. Doté and W.Weise hyp2006 nucl-th/0701050 N.V. Shevchenko et al., Phys. Rev. Lett. 98, 082301 (2007) K- stopped in 12C A. Andronic et al., NPA 765 (2006) 211 V.K. Magas, E. Oset nucl-th/0601013 Search for KNN bound states in HIC at SIS energy

  6. FOPI • - angular coverage close to 4π • - identification of fragments (1 < Z < 12) • - identification of p, d, t, 3He, 4He, , K • - reconstruction of resonances (, K0, , ,...) • 2 high statistic experiments: study of • strangeness production and propagation • - Ni+Ni and Al+Al at 1.9 AGeV (108 Evt, 10 TBytes) The FOPI Detector

  7. High Λ and K0 statistics (> 4·104 counts) • and huge rapidity coverage • - Λ/K0 produced at mid-rapidity • - K+/K0 KaoS - FOPI data in agreement • - Λ colder than protons and emitted from • different region Production of Λ and K0 in Ni+Ni at 1.9 AGeV • No kinetic equilibrium between Λ and p IQMD model: C. Hartnack M. Merschmeyer, X. Lopez et al. (FOPI), submitted to PRC (2007), nucl-ex/0703036

  8. Λ and K0 in Ni+Ni and Al+Al at 1.9 AGeV • Test of kinetic and chemical equilibrium • kinetic temperature • - strange particles systematically colder • than non-strange hadrons • - radial flow in Ni+Ni, almost no expansion in Al+Al • - same kinetical freeze-out temperature in Al+Al • and Ni+Ni (~ 90 MeV) • thermal model reproduce ratios • with T ~ 70 MeV • - kinetical T ~ 90 MeV > chemical T ~ 70 MeV ?? • - limited number of particle species • - need to extend the study to strange resonances • production: , K(892), Σ(1385), ... Al+Al THERM. MOD.: .A. Andronic et al., NPA 772 (2006) 167

  9. K(892) • Measurement of , K(892) and Σ(1385) in • Al+Al at 1.9 AGeV Strange resonances production (1020) preliminary S = 185± 17 S/B = 1.9 MEAN = 1020 MeV/c2 σ = 4 ± 2 MeV/c2 • First sub-threshold measurements • - K(892) (< 800 MeV) • - Σ(1385) (< 400 MeV) • 1-2 counts/105 events ! Σ(1385) short life time resonances should probe finite density X. Lopez et al. (FOPI), submitted to PRL (2007)

  10. A. Andronic, private communication Strange resonances and thermal model 6 independent ratios with 5 strange particles: p, π-, K0, (Λ+Σ0),, K*0(892) and Σ*±(1385) in Al+Al at 1.9 AGeV - canonical ensemble (γs= 1) - adding resonances increase T - the  is not describe at all - chemical T ε [70;80] MeV < kinetical T (90 MeV) preliminary Taking into account strangeness production at SIS leads for Tch ~ [70-80] MeV Difficult to get a clear picture from these model assumptions Need to include γsin the model (fit the ) ? Measurement with an heavier system ?

  11. Σ*±(1385) and K*0(892)in Al+Al at 1.9 AGeV with UrQMD model (M. Bleicher, S. Vogel) - no in medium effect (cascade mode) - production time t ~ 7-8 fm - reconstruction at t ~ 12-15 fm - dominant production channel: Strange resonances and transport model 76% Λ+π→Σ* σ ~ 37 mb 12% Σ+π→Σ* 12% N*(∆)+B →Σ* Σ* 70% K+π→K* σ ~ 20 mb 30% N*(∆)+B →K* K* preliminary Yield of K*(892) over-estimated → measurements allow to fix limits on Kπ & Λπ fusion cross section within this model

  12. Σ*±(1385) and the Chiral Unitary theory (E. Oset) • Σ(1385)→Λπ(Σπ) at ρ= ρ0 • Γ= -2Im[Σ]Σ(1385) = 76 MeV • Mean mass: attractive potential ≈ - 45 MeV Strange resonances and Chiral theory • Σ*±(1385) measurement in Al+Al s½ = 2.7 GeV • - no broadening observed • (PDG values with errors) • - relevance to have a • measurement of Σ(1385) • from heavier systems Murat M. Kaskulov, E. Oset, PRC 73 (2006) 045213 Σ(1385) Al+Al Need to include spectral function in transport codes

  13. Excess observed in Ni+Ni and Al+Al with significance ~ 5 • Interpretation unclear • - final state interaction • - ΣN interaction (2.13 GeV/c2) • - bound state (H-dibaryons) • - partial inv. mass of heavier • state (e.g. 4ΛHe) • Excess located to target • rapidity region → cold protons KNN clusters: search for Λp correlations FINUDA Signal BKG S-B Strange clusters could probe the cold and dense baryonic matter Target cm Proj.

  14. FOPI upgrade and scheduled experiments • FOPI ToF Upgrade: MMRPC • - size: 6 m2 (150 MMRPC) • - channels: 4800 • - t < 100 ps and  < 0.5 cm • - PiD π±, K± up to p = 1 GeV/c • Heavy ion program (2007-2009) • - Ni+Ni and Ni+Pb at 1.9 AGeV • - Ru+Ru at 1.69 AGeV • Elementary processes (2007-2009) • - π beam on p and Pb at 1.7 GeV/c • - p beam on p/d at 3 AGeV resonances production K- flow search for strange clusters K- and  production search for strange clusters

  15. Conclusion / Outlook Strangeness physic at SIS energies with new probes from the medium ! - sub-threshold measurement of K(892), Σ(1385) resonances - K- potential and the  production are not understood - strange multi-baryonic states could probe the cold and dense medium - measurements of resonances from heavier system are already scheduled (2007-2009)

  16. SQM 2007International Conference on Strangeness in Quark Matter The FOPI Collaboration Budapest (Hungary) Bucharest (Romany) Clermont-Ferrand (France) Darmstadt (Germany) Dresden (Germany) Heidelberg (Germany) Lanzhou (China) Moscow (Russia) Munich (Germany) Seoul (South Korea) Split (Croatia) Strasbourg (France) Vienna (Austria) Warsaw (Poland) Zagreb (Croatia) Xavier Lopez, x.lopez@gsi.de

  17. THE END

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