1. The physics of dense baryonic matter investigated with HADES Winter Workshop on Nuclear Dynamics February, 6 – 11, 2011 Winter Park, Colorado Joachim Stroth, Goethe-University Frankfurt / GSI and the HADES collaboration February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI1

2. Agenda o Introduction o Reference measurements (p+p, n+p, C+C) o Ar+KCl collisions at 1.67 GeV/u Dileptons Strangeness o The future at SIS18 and SIS100 o Summary February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI2

3. The HADES Mission Phase 1 (2002 - 2008) -> Upgrade – Light collision systems (limited granularity of TOF system) Phase 2 (2011 – 2015) – Heavy collision systems,  -induced reactions Phase 3 (FAIR/SIS100) – Excitation function up to 10 GeV/u (medium-heavy systems) Search (in this region) for medium-effects partial restoration of chiral symmetry onset of deconfinement  Beam energies of 1-2 GeV/u (2-8 GeV/u at SIS100) February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI3

4. The HADES experiment @ GSI February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI4

5.    p - beams SIS 18 SIS 200 T [MeV] 300 LHC RHIC SPS Partial restoration of chiral symmetry W. Weise et al. + BR scaling (PRL 1991)Motivation February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI5 L. McLerran, R. Pisarski et al.

6. Hot news from the lattice February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI6 Z. Fodor et al., arXiv1102:1356v1 (hep-lat) February 7, 2011

7. Dileptons from light collision systems February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI7

8. The solution to the DLS puzzle?The solution to the DLS puzzle? HADES data in the acceptance of DLS, compared to DLS data. E. Bratkovskaya et al., PLB 2008. Modified description of bremsstrahlung in HSD inspired by Kaptari et al. February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI8

9. Dileptons from pp and np reactions at 1.25 GeV/u: comparison with HSD Data from HADES pp and dp (tagged n) at 1.25 GeV/u Cocktail from HSD calculation 2008 with revised description of Bremsstrahlung HADES collaboration, PLB 690 (2010) 118 February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI9

10. Electron pairs from C+C collisions compared to NN reference HADES collaboration, PLB 690 (2010) 118–122 N N N N  N *, Δ N N N N  N N  NN  February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI10

11. Dileptons from pp and np reactions at 1.25 GeV/u: comparison with One Boson Exchange calculations One Boson Exchange calculations reproduce p+p, but not (yet) n+p ! February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI11 Data from HADES pp and dp (tagged n) at 1.25 GeV/u OBE calculations, different schemes for implementing gauge invariance.

12. Close to a theoretical explanation R. Shyam and U. Mosel arXiv 1006.3873 OBE calculation including pion electromagnetic form factor. February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI12 N N  N *, Δ NN 

13. Dileptons from Ar+KCl at 1.76 GeV/u February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI13

14. Electron pairs from Ar+KCl collisions at 1.76 GeV/uElectron pairs from Ar+KCl collisions at 1.76 GeV/u First observation of  mesons in HI collisions at these (SIS) energies HADES collaboration, Nucl.Phys.A830:483C-486C,2009 Fit: exponential + gaussian 30-40 counts In peak! February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI14

15. Excess radiation in Ar+KCl at 1.76 GeV/u Compared to reference after subtraction of contributions from   Indication for radiation from the medium.  Multistep processes or multi-particle correlation. R R  N N  N N N N  R e-e- e+e+ N N February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI15

16. Data for  0 and  from TAPS collaboration Dilepton excess scales with beam energy like  production C+C (DLS) C+C (HADES) Ca+Ca (DLS) Ar+KCl (HADES) Systematics of the excess yield Excess yield scales stronger than linear with A part February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI16

17. Refined HSD vacuum calculation o Enhanced bremsstrahlung from elastic NN collisions according to “Kaptari-Kämpfer” (OBE) prescription. o Reduced vector-meson production via the LUND string model in order to better match pp exp. data. o Improved isospin dependence of the channels NN-> V+NN and  +N-> V+N. HSD, November 2009 release “It’s a bingo” February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI17

18. 18 Dileptons from pp at 3.5 GeV HSD, Nov. 09 release K. Schmidt, et al. Phys. Rev. C 79, 064908 (2009) Normalized to π peak February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI

19. Transverse mass spectra in invariant mass bins February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI19 Significant change in slope when invariant mass grows

20. Dilepton production in pp at 3.5 GeV Particle production by LUND string fragmentation Particle production through baryonic resonances February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI20

21. Where is the  February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI21 Two-component quark model (Wan/Iachello, IJMP A20, 2005) used for the  -Dalitz. p+p 3.5 GeV

22. Dileptons from HI reactions in theory Thermal dilepton rate... isentropic expansion... or from transport In future: combine the best of the two worlds! February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI22 q q q q q q q q q q q q e e

23. strangeness February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI23

24. Strangeness production in 1.75 GeV/u Ar+KCl reactions Λ 0s0s -- High-statistics measurement of       and   but also:  0 s →      → p  -  →      - →   - HADES collaboration: Phys.Rev.Lett.103:132301,2009 Eur.Phys.J.A40:45-59,2009 Phys.Rev.C80:025209,2009 February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI24

25. HADES data and the SHM Particle multiplicities largely in accordance with SHM o  yield explained (non-strange particle ) o  − underestimated by SM ■ Ar+KCl at 1.76 GeV/u THERMUS fit S.Wheaton and J.Cleymans, J.Phys.G31(2005)S1069 T= 73  6  b =770  43 (MeV) R C =2.4  0.8 fm R fireball =4.9  1.4 fm  2 =2.1 (no  - ) J.Cleymans priv. communication February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI25

26.  /  -ratio M  (→ K + K - ) : (2.6 ± 0.7) ·10 -4 M  (→ e + e - ) : (6.7 ± 2.7) ·10 -3 In accordance with SHM. No OZI suppression in the production. February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI26

27. Multi-strange baryons Probability (M ss ) to produce in Ar+KCl collisions a strange quark pair is ≈ 5 × 10 -2. q q q q q q q q q q q q q q q q q q q q q q q q Bag fusion  quarkyonic matter? Strange quarks “trapped” in bubbles? February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI27

28. The HADES upgrade … … from 8   /day (Ar+KCl) to 170   /day (Ag+Ag) and dilepton statistics like NA60 February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI28

29. The RPC time-of-flight systemThe RPC time-of-flight system Full-system test results:  t  78 ps  x  8 mm  ~ 97% D. Belver et al. NIM A602(2008) 687, 788 E. Blanco et al. NIM A602(2008) 691 RPC D. Belver et al. NIM A602(2008) 687, 788 E. Blanco et al. NIM A602(2008) 691 Leading institute: Coimbra, Portugal February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI29

30. The new HADES DAQ System The new HADES DAQ System CTS VME CPU MU... RPC F. Wall MDC RICH Shower VULOM3 Start, Veto TOF Ethernet To the Front End Electronics Fröhlich et al., IEEE Trans. Nucl.Sci. Vol. 55, Issue 1 (2008) 59 February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI30 Commissioning run (Au+Au) November 2010: 20 KHz Trigger rate and 500 Mb/s to disk

31. Current proposal 2011-2015 (campaigns min.): Dielectron & strangeness production in heavy systems low mass (0.15<M e+e- <0.5) excess studies vector meson spectroscopy  /K  production: differential distributions, y, p t (increased acceptance due to RPC !), flow  - production characteristics  induced reactions on p and A February 6-11, 2011 Joachim Stroth, Goethe-Univ./GSI 31

32. Towards FAIR February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI32

33. Summary – „Long-lived“ states of dense nuclear matter are produced in collisions of heavy ion at energies of a few GeV/u. – The phase in the high-density region might be much more exotic then a hadron/resonance gas. – Unfortunately, there is no smoking gun, but: Fast equillibration „Sub-threshold“ production Strong broadening of in-medium states – Close collaboration with, and novel approaches in theory are necessary to make the case. Joachim Stroth, Goethe-Univ./GSI

34. The HADES collaboration LIP-Laboratório de Instrumentação e Física Experimental de Partículas, 3004-516 Coimbra, Portugal Smoluchowski Institute of Physics, Jagiellonian University of Cracow, 30-059 Kraków, Poland GSI Helmholtzzentrum für Schwerionenforschunm, 64291 Darmstadt, Germany Institut für Strahlenphysik, Forschungszentrum Dresden-Rossendorf, 01314 Dresden, Germany Joint Institute of Nuclear Research, 141980 Dubna, Russia Institut für Kernphysik, Johann Wolfgang Goethe-Universität, 60438 Frankfurt, Germany II.Physikalisches Institut, Justus Liebig Universität Giessen, 35392 Giessen, Germany Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow, Russia Physik Department E12 & Excellence Cluster Universe, TUM, 85748 München, Germany Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus Institut de Physique Nucléaire (UMR 8608), CNRS/IN2P3 - Université Paris Sud, F-91406 Orsay Cedex, France Nuclear Physics Institute, Academy of Sciences of Czech Republic, 25068 Rez, Czech Republic Departamento de Física de Partículas, University of Santiago de Compostela, 15782 Santiago de C.a, Spain February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI34

35. Thank you February 6-11, 2011Joachim Stroth, Goethe-Univ./GSI35