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Dubna, November 2003Joachim Stroth Hadron Structure in Dense Nuclear Matter Vector mesons Di-electron spectroscopy in heavy ion collisions The HADES spectrometer......

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Presentation on theme: "Dubna, November 2003Joachim Stroth Hadron Structure in Dense Nuclear Matter Vector mesons Di-electron spectroscopy in heavy ion collisions The HADES spectrometer......"— Presentation transcript:

1 Dubna, November 2003Joachim Stroth 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

2 Dubna, November 2003Joachim Stroth A photon...

3 Dubna, November 2003Joachim Stroth... hadronizes...

4 Dubna, November 2003Joachim Stroth.... hadronizes via Vector Meson Dominance

5 Dubna, November 2003Joachim Stroth Di-electron Spectroscopy in Heavy Ion Collisions p n ++ K p Penetrating probes: information from the early stage low branching ratio, O (10 -5 ) e+e+ e-e-

6 Dubna, November 2003Joachim Stroth Nuclear matter under extreme conditions DATA: Fit of statistical model to measured abundances in the final state P. Braun-Munzinger, J. Stachel et al.

7 Dubna, November 2003Joachim Stroth Reasons for Medium Modifications Meson self energy in medium many more degrees of freedom (spreading) Broadening !? Dynamical mass generation by spontaneous Chiral Symmetry breaking –m q 10 MeV (current quark mass) –m u,d m p,n / 3 300 MeV (constituent quark mass) mass shift !?

8 Dubna, November 2003Joachim Stroth 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)

9 Dubna, November 2003Joachim Stroth QCD: Anregungsspektrum ?Wie entstehen aus (nahezu) masselosen Quarks Hadronen mit Massen von typisch 1 GeV und mehr? !Die Chirale Symmetrie ist im Grundzustand der QCD spontan gebrochen! Leichte Mesonen (M<<1 GeV),, K Keine Paritätsdupletts z.B. M( ) M(a 1 ) Durch Kopplung der Quarks an die virtuellen Quark-Antiquarkpaare des chiralen Kondensats erhalten sie dynamisch eine Masse (1232) (1600) k, p,n N (1440) N (1520) M [GeV] 0 1 a1a1 Vakuum 0 Mesonen Baryonen k, p,n N (1440) N (1520) M [GeV] 0 1 a1a1 Mesonen Baryonen 0 k, N (1440) N (1520) M [GeV] 0 1 Mesonen Baryonen a1a1 p,n 0

10 Dubna, November 2003Joachim Stroth Modification of meson spectral function through coupling to resonances Nuclear Physics A, Volume 632, 9 March 1998, W. Peters, M. Post, H. Lenske, S. Leupold and U. Mosel Modification of the -Meson spectral function depends on.... relative momentum to the medium the density of the surrounding medium normal nuclear ground state density twice

11 Dubna, November 2003Joachim Stroth 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

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

13 Dubna, November 2003Joachim Stroth 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.)

14 Dubna, November 2003Joachim Stroth High acceptance dielectron spectrometer HADES Geometry Six sectors form a hexagonal frustum: in, in, pair acceptance Tracking Superconducting toroid (6 coils) –B max = 0.7 T, –Bending power 0.34 Tm MDC (multiwire drift chamber) –Low mass design –four planes of small cell ( cm drift chamber. Lepton identification & trigger RICH –Radiator: C 4 F 10 –Spherical mirror –Photon Detector: CsI photo cathode META (TOF & Pre-Shower) –TOF plastic scintillators –Lead Shower detector LVL2 trigger on Electrons –Fast (~200 s) –Highly selective (suppression up to1/100)

15 Dubna, November 2003Joachim Stroth

16 Dubna, November 2003Joachim Stroth Omega production in A Selective measurement of medium modification ant nuclear ground state density uncertainties in calculations (interferences, el. form- factors, res N *, ) needs data from e+ e- 208 Pb - HADES W.Schoen et al. Acta Phys.PolB27(1996)2959 M.Effenberger et al. Nucl-th/9901039

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

18 Dubna, November 2003Joachim Stroth Electron identification using the RICH hadron contamination < 2% p/ separation for p < 1000 MeV/c C+C, 2AGeV p*q [MeV/c] v/c Tracking+TOF q*p [MeV/c] v/c

19 Dubna, November 2003Joachim Stroth Tracking with the drift chambers and more FE electronics threshold t1t2 drift cell

20 Dubna, November 2003Joachim Stroth Hadronenspektroskopie Arbeit von Peter Zumbruch, GSI Flache Akzeptanz über einen weiten Bereich des Phasenraums Pionen Protonen

21 Dubna, November 2003Joachim Stroth Pairs from C+C @2 AGeV Nov02 (60% of data) CB M e+e- [MeV/c 2 ] Counts/10 MeV CB combinatorial background ! no close pair rejection signal CB Preliminary

22 Dubna, November 2003Joachim Stroth Nov02 Preliminary Nov01 Nov02 data scaled down by 10 0 e + e - M e+e- [MeV/c 2 ] Nov02 C+C @2 AGeV Counts/MeV shapes of the inv. mass distributions are consistent 50k pairs in Nov02 (60% of data) Nov02: 4 sectors equipped with outer MDC Not acceptance corrected

23 Dubna, November 2003Joachim Stroth Signal pairs from C+C M e+e- [MeV/c 2 ] dN/dM[1/MeV] M e+e- [MeV/c 2 ] CB subtracted but not acceptance corrected ! normalized by number of LVL1 triggers different magnetic field settings for 1AGeV 1 AGeV 2 AGeV Preliminary

24 Dubna, November 2003Joachim Stroth Nuclear matter at the highest densities The future Compressed Baryonic Matter Experiment

25 Dubna, November 2003Joachim Stroth Di-electron spectroscopy at the future facility Radiation hard Silicon pixel/strip detectors magnet 1 m

26 Dubna, November 2003Joachim Stroth HADES at SIS 100 Electrons from Dalitz (pt vs y) HADES at SIS 100 e+ e- 1010 1010 0 3 e+ e- 0 3 2 GeV/u 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 C+C

27 Dubna, November 2003Joachim Stroth with CBM 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

28 Dubna, November 2003Joachim Stroth 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

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