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Analysis of X-Production in Pb+Pb Collisions at 40A GeV at SPS

This study by Christine Meurer presents an analysis of X-particle production in lead-lead collisions at 40A GeV at the Super Proton Synchrotron (SPS). The motivation lies in understanding the hadronization features of heavy ion collisions through the investigation of multiple strange particles. The experiment conducted by the NA49 collaboration focuses on examining changes in X-production concerning collision centrality and beam energy. Results show the centrality and energy dependence of the X+/X- ratio, reflecting variations in baryon density. The presentation covers the NA49 experiment, analyzed data sets, X-analysis methodology, and significant findings. Christine Meurer provides insights into the importance of these results and hints at future research directions.

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Analysis of X-Production in Pb+Pb Collisions at 40A GeV at SPS

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  1. X-and X+production in Pb+Pb collisions at 40AGeV at SPS Christine Meurer J.-W.-Goethe-Universität Frankfurt/Main for the NA49 collaboration

  2. 1. Outline • Motivation • NA49 experiment • Analyzed data sets and centrality bins • X –analysis • Results: • Centrality dependence of X+/X--ratio • Energy dependence of X+/X--ratio • Summary and outlook Christine Meurer

  3. 2. Motivation • Measurement of multiple strange particles provide important information on hadronization features of heavy ion collisions • Looking for qualitative changes (onset phenomena), when varying: • System size • Energy density • Study of X -production as function of: • Collision centrality • Beam energy • X+/X-–ratio reflects changes in baryon density Christine Meurer

  4. 3. NA49 experiment Veto-Calorimeter for centrality selection Christine Meurer

  5. 4. Analyzed data sets • Pb+Pb (minimum bias) at 40AGeV • (Pb+Pb (7% most central) at 40AGeV, Nevt = 700,000, still to be analysed) 1 2 3 4 5 6 central  peripheral Christine Meurer

  6. Geometrical cuts are used to reduce the background: Impact parameter of X Impact parameter of L Decay position of X Proton selection by dE/dx 5. X-analysis Invariant mass-spectra at mid-rapidity X-mass = 1.321 Christine Meurer

  7. 6. Phase space population 1.–4. centrality bin: Measured X- pt > 0.3 5.+6. centrality bin: pt > 0.0 mid-rapidity = 2.2 Christine Meurer

  8. 7. Invariant mass spectra at mid-rapidity central mid central peripheral X- X+ Christine Meurer

  9. 8. Centrality dependence of X+/X--ratio • The X+/X--ratio has only a weak centrality dependence at 40AGeV preliminary Christine Meurer

  10. 9. Energy dependence of X+/X--ratio • The X+/X--ratio increases with the energy • All ratios at mid-rapidity • All ratios for central collisions • Reflecting decreasing baryon density preliminary Christine Meurer

  11. 10. Hadron-gas model (F. Becattini et al.) • The HG model (with partial strangeness saturation) predicts: X+/X-= 0.06 (4p) • Measured: X+/X-= 0.11 ± 0.02 (mid-rapidity) Close to hadron-gas model prediction Christine Meurer

  12. 11. Summary and outlook • First results on centrality dependence of Xs at 40AGeV from NA49: • Weak centrality dependence of X+/X--ratio • The X+/X- -ratio increases with the energy • Measured X+/X--ratio is close to the hadron-gas model • Outlook: • Corrected spectra for X- and X+ at 40AGeV • 4p yields (40AGeV) • X-analysis at 20,30 and 80AGeV Christine Meurer

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