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Hyperon simulations

Hyperon simulations. E. Kryshen (PNPI, SPbSPU) Ya. Berdnikov (SPbSPU). Charged decays. CBMROOT framework OCT04 UrQMD central events 25 AGeV Magnetic field v03b Strip hits with 10 μ m resolution No particle ID is assumed Ideal track finding (at least 4 MC points)

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Hyperon simulations

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  1. Hyperon simulations E. Kryshen (PNPI, SPbSPU) Ya. Berdnikov (SPbSPU)

  2. Charged decays CBM Collaboration meeting

  3. CBMROOT framework OCT04 UrQMD central events 25 AGeV Magnetic field v03b Strip hits with 10 μm resolution No particle ID is assumed Ideal track finding (at least 4 MC points) Momentum and vertex reconstruction with Kalman filter 4-order Runge-Kutta extrapolation in magnetic field(Resolution on daughter momentum: ~ 0.6%) Event mixing used for - and -background simulation - and - signal was generated in accordance with UrQMD pt-y distributions Simulation framework CBM Collaboration meeting

  4. Acceptance -- Total for : 15.8% Total for : 6.7% Total for : 7.7% CBM Collaboration meeting

  5. Signal distribution --  = 0.78 MeV  = 0.90 MeV  = 1.02 MeV CBM Collaboration meeting

  6. Secondary vertex resolution • Z-vertex resolution: • : 0.34 mm • : 0.44 mm • : 0.36 mm CBM Collaboration meeting

  7. Applying cuts • The following variables were considered to cut the background: • bpp – impact parameter of accepted particles • pca – z position of secondary vertex • dca – distance of closest approach • bla – impact parameter of pair momentum Background c+c-, no cuts Statistics: 500 events CBM Collaboration meeting

  8. Illustration of cut parameters CBM Collaboration meeting

  9. Illustration of pair impact parameter cut CBM Collaboration meeting

  10. Cut parameter distributions Distance of closest approach Impact parameter for positive tracks All pairs All positive protons  pairs CBM Collaboration meeting

  11. Optimised cut parameters,  Statistics: 104 events CBM Collaboration meeting

  12. Selection of  candidates • Cuts: • Impact parameter cut for positive and negative particles (0.05 cm) • Invariant mass cut in the range 2, =0.78 MeV/c2 • Efficiency: • -: 83.3 % • -: 81.9 % • About 15  candidates after cut CBM Collaboration meeting

  13. Optimised cut parameters, - Statistics: 8∙105 events CBM Collaboration meeting

  14. Optimised cut parameters, - Statistics: 5.8∙105 events CBM Collaboration meeting

  15. Invariant mass distributions after cuts -- CBM Collaboration meeting

  16. Reconstruction of initial spectra Initial spectrum,  Reconstructed spectrum,  CBM Collaboration meeting

  17. Reconstructed distributions  y = 1.0 – 1.2 y = 1.8 – 2.0 Yield UrQMD: 40.5 Yield reconstructed: 40.3 Statistics: 104 events CBM Collaboration meeting

  18. Reconstructed distributions - y = 1.2 – 1.4 y = 1.8 – 2.0 Yield UrQMD: 0.98 Yield reconstructed: 0.95 Statistics: 8∙105 events CBM Collaboration meeting

  19. Further cut optimisation Simulations with realistic track finding Study the influence of mass and topological constraints on the momentum and invariant mass resolution Acceptance vs magnetic field analysis Future steps CBM Collaboration meeting

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