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Hadron Structure in Dense Nuclear Matter

Hadron Structure in Dense Nuclear Matter. Vector mesons Di-electron spectroscopy in heavy ion collisions The HADES spectrometer ... ... and the future of di-electron spectroscopy Summary. A photon. .... hadronizes via Vector Meson Dominance. n. . p. p. . . r. e +.  ++. K.

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Hadron Structure in Dense Nuclear Matter

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  1. Hadron Structure in Dense Nuclear Matter Vector mesons Di-electron spectroscopy in heavy ion collisions The HADES spectrometer ... ... and the future of di-electron spectroscopy Summary Joachim Stroth

  2. A photon ... Joachim Stroth

  3. .... hadronizes via Vector Meson Dominance Joachim Stroth

  4. n  p p   r e+ ++ K e- Di-electron Spectroscopy in Heavy Ion Collisions Penetrating probes: • information from the early stage • low branching ratio, O (10-5) Joachim Stroth

  5. Nuclear matter under extreme conditions DATA:Fit of statistical model to measured abundances in the final state P. Braun-Munzinger, J. Stachel et al. Joachim Stroth

  6. Meson self energy in medium many more degrees of freedom (spreading) Broadening !? Dynamical mass generation by spontaneous Chiral Symmetry breaking mq10 MeV (current quark mass) mu,dmp,n / 3  300 MeV(constituent quark mass) mass shift !? Reasons for Medium Modifications Joachim Stroth

  7. Time dependence of the Chiral Condensate B. Friman et al.: Eur. Phys. J. (1998) Method: quark-gluon string model (Toneev at al. NP A519(1990)463c) Joachim Stroth

  8. Nuclear Physics A, Volume 632, 9 March 1998, W. Peters, M. Post, H. Lenske, S. Leupold and U. Mosel Modification of the r-Meson spectral function depends on.... relative momentum to the medium the density of the surrounding medium Modification of meson spectral function through coupling to resonances normal nuclear ground state density twice Joachim Stroth

  9. Di-electrons measured with DLS at Berkeley • Daten: R.J. Porter et al.: PRL 79(97)1229 • Modell: E.L. Bratkovskaya et al.: NP A634(98)168, BUU, Spektralfunktionen im Vakuum DLS Joachim Stroth

  10. Extended Vector Meson Dominance Still experimental data in the low mass region above the theoretical expectation Shekhter et al., PRC 68 (2003) Joachim Stroth

  11. Bratislava (SAS, PI), Catania (INFN - LNS), Cracow (Univ.), Darmstadt,(GSI), Dresden (FZR), Dubna (JINR, LHE), Frankfurt (Univ.),Giessen (Univ.), Milano (INFN, Univ.), Moscow (ITEP, INR, MEPhI), Munich (Tech. Univ.), Nicosia (Univ.), Orsay (IPN),Rez (CAS, NPI), Sant. de Compostela (Univ.), Valencia (Univ.) Joachim Stroth

  12. Geometry Six sectors form a hexagonal frustum: 2p in f, 18 < J < 85 35 % pair acceptance Tracking Superconducting toroid (6 coils) Bmax = 0.7 T, Bending power 0.34 Tm MDC (multiwire drift chamber) Low mass design four planes of small cell (» 1 cm) drift chamber. Lepton identification & trigger RICH Radiator: C4F10 Spherical mirror Photon Detector: CsI photo cathode META (TOF & Pre-Shower) TOF plastic scintillators Lead Shower detector LVL2 trigger on Electrons Fast (~200 ms) Highly selective (suppression up to1/100) High acceptance dielectron spectrometer HADES Joachim Stroth

  13. Joachim Stroth

  14. e+ 208Pb -  e- Omega production in A Selective measurement of medium modification ant nuclear ground state density M.Effenberger et al. Nucl-th/9901039 W.Schoen et al. Acta Phys.PolB27(1996)2959 HADES • uncertainties in calculations (interferences, el. form-factors, res N*,) • needs data from Joachim Stroth

  15. The current experimental program of HADES 11/2002: Commissioning (12C+12C) • 36 M events • no outer drift chambers 11/2002: Production run (12C+12C) • 200 M events, 44 % LVL2 triggered • 4 Sectors with outer tracking(4/2) 10/2003:Commissioning (p+lH2) • 6 Sectors with outer tracking (6/4) 02/2004: Production run (p+lH2) Joachim Stroth

  16. C+C, 2AGeV Electron identification using the RICH Tracking+TOF • hadron contamination <2% • p/ separation for p < 1000 MeV/c v/c v/c p*q [MeV/c] q*p [MeV/c] Joachim Stroth

  17. threshold Tracking with the drift chambers and more FE electronics drift cell t1 t2 Joachim Stroth

  18. CB combinatorial background • no close pair rejection Pairs from C+C @2 AGeV Preliminary Nov02 (60% of data) signal CB CB Counts/10 MeV Me+e- [MeV/c2] Joachim Stroth

  19. Preliminary 0e+e- Nov02 data scaled down by 10 Nov02 Nov01 Nov02 C+C @2 AGeV Not acceptance corrected Counts/MeV Me+e- [MeV/c2] • shapes of the inv. mass distributions are consistent • 50k pairs in Nov02 (60% of data) • Nov02: 4 sectors equipped with outer MDC Joachim Stroth

  20. Signal pairs from C+C Preliminary 1 AGeV 2 AGeV dN/dM[1/MeV] Me+e- [MeV/c2] Me+e- [MeV/c2] • CB subtracted but not acceptance corrected ! • normalized by number of LVL1 triggers • different magnetic field settings for 1AGeV Joachim Stroth

  21. The futureCompressed Baryonic Matter Experiment Nuclear matter at the highest densities Joachim Stroth

  22. magnet Radiation hard Silicon pixel/strip detectors Di-electron spectroscopy at the future facility 1 m Joachim Stroth

  23. e+ e- e+ e- 1 0 1 0 0 3 0 3 0 3 0 3 Electrons from h Dalitz (pt vs y) HADES at SIS 100 2 GeV/u C+C 8 GeV/u • particle multiplicity higher in forward region • pion acceptance by 20-30% lower at 8 GeV/u than at 2 GeV/u • single lepton (from eta Dalitz) acceptance by 10-20% lower • dilepton acceptance by 20% lower Joachim Stroth

  24. Feasibility study :   e+ e- with CBM • CBM experimental concept: • Electron identification after tracking! • Background from  conversion dominates • e+e- vertex cuts is essential: • SNR  3 in 1 M events • study ongoing, tracking needed Joachim Stroth

  25. Summary Dielectrons are ideal probes for the dense phase of nuclear matter. Creation and propagation well understood (QED). • High penetrability • The disadvantage of small branching ratios can partly be compensated by using state of the art micro electronics First results of the HADES spectrometer are arriving • Conduct systematic investigation of heavy collisions up to 2 GeV/u • Complemented by a series of experiments using proton and pion beams The future accelerator facility will provide ideal conditions to create nuclear matter at the highest densities • HADES can cover beam energies up to 8 GeV/u • Conceptually new technique for dielectron spectroscopy with CBM Joachim Stroth

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