1. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 1 Challenges in Physics & Instrumentation Results from Heavy Ion and Elementary Reactions Summary & Outlook Dilepton Measurements with HADES Christian Müntz (Univ. Frankfurt), for the HADES Collaboration

2. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 2 The Collaboration GSI SIS  Catania (INFN - LNS), Italy  Cracow (Univ.), Poland  Darmstadt (GSI), Germany  Dresden (FZD), Germany  Dubna (JINR), Russia  Frankfurt (Univ.), Germany  Giessen (Univ.), Germany  Milano (INFN, Univ.), Italy  Munich (TUM), Germany  Moscow (ITEP,MEPhI,RAS), Russia  Nicosia (Univ.), Cyprus  Orsay (IPN), France  Rez (CAS, NPI), Czech Rep.  Sant. de Compostela (Univ.), Spain  Valencia (Univ.), Spain  Coimbra (Univ.), LIP, Portugal

3. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 3 © A.Drees Orientation Sources for dilepton production in (ultra-) relativistic HICs Add… Accuracy Significance Systematics

4. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 4 1020 30 t [fm/c] ≈ 10 fm/c Physics Motivation Vector mesons (VM)Optimum choice! Vector mesons (VM): Optimum choice! VM life time comparable to system life time Interplay with baryonic resonances Decay in dileptons: Direct probe, final state interaction minimized! The SIS heavy ion energy regime: Probing nuclear matter at “moderate”… - Densities (  /  o = 1…3), and - Temperatures (T < 100 MeV) A long life time of the dense system (up tp 10 fm/c) The all-dominant presence of baryonic resonances (“resonance matter”,  33 ), N  /A part ≈ 10% The sub-threshold production of Kaons and Vector Mesons: Multi-step processes confined to the dense phase

5. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 5 The Mission High Acceptance DiElectron Spectrometer Focus on the spectroscopy of vector mesons (  ) Consistent picture in pp, pA,  A and AA reactions Supplemented by hadron spectroscopy, incl. K 0 s, ,  Instrumental challenge! VM: rare probe: 1 VM per 1-10 Million reactions! Large background from conversion and  0 -Dalitz decay Spectrometer with a … High geometric acceptance & invariant mass resolution High background rejection & rate capability, dedicated LVL2 trigger

6. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 6 The Setup START Acceptance: Full azimuth, polar angles 18 o - 85 o Pair acceptance  0.35 About 80k detector channels Forward Hodoscope  <7 o Side View Opening angle > 9 o Pair acceptance

7. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 7 Completed Runs Physics Runs in… p, d,  - induced A + AStatus/Comment 2002C + C 2 AGeVPublished! 2004C + C 1 AGeVAnalysis finished 2004p + p 2.2 GeVAnalysis finished 2005Ar + KCl 1,75 AGeVAnalysis ongoing 2006p + p 1.25 GeVAnalysis ongoing 2007p + p 3.5 GeV d + p 1.25 AGeV … online results! 2008p + A 3.5 GeV 2008/9Upgrade RPC, DAQ 2009Ni + NiPlanned 2010  + N, A 2011Au + Au > 2011Hades goes FAIR (8 AGeV)

8. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 8 Hadrons: Advances in Particle ID Standard PID via time-of-flight & momentum New New: dE/dx from tracking (MDC) Dedicated cuts to increase (e.g. kaon) signal. MDC IMDC IIMDC IIIMDC IV Truncated mean is calculated from all measurements of a track particle track K+K+ p ++ -- K-K- Ar + KCl, 1.75 AGeV

9. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 9 Ar + KCl, 1.75 AGeV Ar + KCl, 1.75 AGeV Invariant mass distributions 30% of total statistics Preliminary! Mixed event technique background (K s o,  ) PhD thesis A.Schmah

10. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 10 Hadrons: Charged Pions C + C, 2 AGeV Anisotropy: Used for the Normalization of dilepton spectra, properly extrapolated to 4  π+π+ y = 0.1-0.2 0.2-0.3 0.3-0.4 0.4-0.5 0.5-0.6 0.7-0.8 0.8-0.9 0.9-1.0 1.0-1.1 1.1-1.2 1.2-1.3 1.4-1.5 1.5-1.6 1.6-1.7 1.7-1.8 *) 11% syst, error, in agreement with KaoS, TAPS **) preliminary 1 AGeV **)2 AGeV *) N /A part 0.069 ± 0.0080.137 ± 0.015

11. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 11 Details moved to the backup slides…! Lepton candidate selection Spatial correlations PID Background rejection Conversion  0 -Dalitz Combinatorial background Same event like sign pairs Mixed event opposite sign pairs Lepton Analysis: Technicalities  e+e+ e-e-  ~ 0.7 0 Conversion e+e+ e-e- 00   ~ 2.2 0 Dalitz

12. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 12 C + C, 2 AGeV, vs. Hadronic Cocktail ► Cocktail A: ► Cocktail A:  0 + η + ω (long lived) ► Cocktail B: A & ► Cocktail B: A & Δ(  Ne+e-), ρ (short lived) 18 % 21 % systematic errors: 15 % - efficiency correction 10 % - combinatorial background 11 % -  0 normalization PhD thesis: M. Sudol PRL 98, 052302 (2007) -Normalized to ½(  + +  - ) yield -M <150 MeV/c 2 : ~23000 counts -M - ≥150 MeV/c 2 : ~ 3000 counts -  (M ee ) ~9 % @ M ee ~0.8 GeV/c 2 Event generator PLUTO Event generator PLUTO : thermal source (T=80MeV)  polar angle distribution from charged  analysis η (TAPS data)  ρ, ω: m  -scaling Δ scales with 

13. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 13 p ┴, y distributions compared to cocktail ► C + C, 2 AGeV

14. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 14 C + C, 1 AGeV, preliminary data Preliminary! -Normalized to ½(  + +  - ) yield -M <150 MeV/c 2 : ~17780 counts -M - ≥150 MeV/c 2 : ~ 646 counts Event generator PLUTO Event generator PLUTO : Thermal source (T=55MeV)  polar angle distribution from charged  analysis η (TAPS data)  ρ, ω: m  -scaling Δ scales with  22-25 % systematic errors: 20 % - efficiency correction 10 % - combinatorial background 11 % -  0 normalization PhD thesis: Y. Pachmayer, T. Christ ► Cocktail B: A & ► Cocktail B: A & Δ(  Ne+e-), ρ (short lived) PRELIMINARY ► Cocktail A: ► Cocktail A:  0 + η + ω (long lived)

15. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 15 Comparison 1 – 2 AGeV PRELIMINARY

16. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 16 PRELIMINARY Comparison 1 – 2 AGeV Inv. Mass spectrum normalized to hadronic cocktail of long lived mesonic components Agreement @ M ee < 0.15 GeV/c 2. Large relative excess compared to cocktail A, similar in shape. Quantitative analysis: deduce the absolute excess yield Y exc (beyond η), making use of the TAPS η data: Excess scales like pions. Excess (beyond η) scales like pions.DLS… C + C 2 AGeV Phys. Rev. Lett. 98, 052302 (2007) TAPS: Y exc (2.0)/Y exc (1.0) = 2.3 ± 0.6(stat) ± 1.0(sys)

17. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 17 1 AGeV: Comparison to DLS Different phase space Different phase space coverage of HADES and DLS Extrapolation Extrapolation of HADES data: Inspired by the thermal model HADES & DLS Filters applied Processed separately for low (M<150GeV/c 2 ) and high inv. masses DLS Data: R.J. Porter et al.: PRL 79(97)1229 PRELIMINARY DLS data (C+C, 1AGeV) confirmed by HADES!

18. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 18 p ┴ Distributions compared to the Cocktail PRELIMINARY J. Carroll – presentation International Workshop on Soft Dilepton Production August 20-22,1997, LBNL

19. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 19 Heavy Ion → Elementary Reactions C + C summary: DLS data confirmed Significant excess @ M ee > 150 MeV/c 2 -Energy excitation function like pions. -Evidence for missing yield @ low-p t Contributions of pN Bremsstrahlung and N*(  ) decay? No precise data available! (N*(  )  Ne + e - BR, EM transition FF) Measure elementary reactions, e.g.: DiElectron sources in pn, pp below the η threshold Measure pp  + p  ppe + e - (fix  +,  brems (pp) is small) Measure pn  e + e - X with dp reactions →  brems (pn) -Experimental technique: tag projectile spectator protons!

20. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 20 p+n tagging in d+p reactions Installation of the (rearranged) Forward Hodoscope FH, formerly used at Bevalac and KaoS/SIS (for event plane analysis). p_spec pTpT d pTpT FH, Θ < 7 o, added 2007 (n) LH 2 target (Orsay) pp contamination 10% only. May 2007 Preliminary online results from May 2007 ToF-Tagging of the projectile spectator proton with the Forward Hodoscope FH (Θ < 7 o ).

21. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 21 p+p, p+n  e + e - X, 1.25 GeV Not corrected for efficiency; in the HADES acceptance, 50% of available statistics Red line: Pluto hadronic cocktail (properly treated for acceptance/efficiency) Only 2 sources:  0  e + e - ,  +  pe + e - (BR=4.4*10 -5 ) (  + yield fixed to  0 with isospin relation: N(  + )=3/2 N(  0 )) PRELIMINARY n + p, 1.25 GeV  e+e- > 9 0 PhD thesis T.GalatyukOnline spectrum ► Factor 2 (pp), 4-5 (np) missing for M > 150 MeV/c 2 ► Evidence for additional sources !

22. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 22 Online: p+p, 3.5 GeV May 2007 May 2007, preliminary, online results! No final calibration/alignment! e + e - pair analysis e + e - pair analysis:  not shifted! Preliminary calibration… Extra yield below VM pole mass. S/B 10 1 0.5 1.0 0.5 1.0 M ee M ee Preliminary PRELIMINARY

23. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 23 Summary & Outlook Physics Runs in… p, d,  - induced A + AStatus/Comment 2002C + C 2 AGeVPublished! 2004C + C 1 AGeVAnalysis finished 2004p + p 2.2 GeVAnalysis finished 2005Ar + KCl 1,75 AGeVAnalysis ongoing 2006p + p 1.25 GeVAnalysis ongoing 2007p + p 3.5 GeV d + p 1.25 AGeV … online results! 2008p + A 3.5 GeV 2008/9Upgrade RPC, DAQ 2009Ni + NiPlanned 2010  + N, A 2011Au + Au > 2011Hades goes FAIR (8 AGeV) ►HADES took off and is contributing with high-quality data to the understanding of the di-electron production in heavy ion collisions in the SIS energy regime, characterized by VM production close to the threshold and the crucial role of baryonic resonances. ►The physics program will be continued by aiming at heavier systems and pion-induced reactions.

24. Christian Müntz (Univ. Frankfurt) for the HADES Collaboration, CPOD 2007 24 Towards FAIR HADES 2 – 8 AGeV CBM 8 – 45 AGeV