1 / 21

Witold Przygoda, Jagiellonian University, Cracow, for the HADES Collaboration

2nd International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions, Asilomar CA, 2006. HADES experiment: dilepton spectroscopy in C+C (1 and 2 AGeV) collisions Motivations - HADES Dielectron analysis strategy Results & models comparison C+C 2 AGeV C+C 1AGeV.

gittel
Télécharger la présentation

Witold Przygoda, Jagiellonian University, Cracow, for the HADES Collaboration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 2nd International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions, Asilomar CA, 2006 HADES experiment: dilepton spectroscopy in C+C (1 and 2 AGeV) collisionsMotivations - HADESDielectron analysis strategyResults & models comparisonC+C 2 AGeVC+C 1AGeV Witold Przygoda, Jagiellonian University, Cracow, for the HADES Collaboration

  2. Partial restoration of chiral symmetry Additional self-energy terms due to meson-baryon coupling SPS g,p-,p - beams RHIC LHC SIS 18 SIS 200 T [MeV] 300 W. Weise et al. Motivation Brown-Rho scaling Probe the electromagnetic structure of hot and dense nuclear matter in the time-like region What are the relevant observables as nuclear density and/or temperature increase?

  3. ≈ 10 fm/c • Particle productionat or below threshold : • co-operative processes • (i.e. multi step processes) • production confined to the • high density phase ! NN → NΔ T. Renk et al., PRC 66 (2002) 014902 30 10 20 t [fm/c] πN πN → ρ N multi step processes: i.e. The case of moderate beam energies Vector meson spectroscopy – in-medium effects investigation Baryon density: Dt(r/r0 > 2) ≈ 10 fm/c comparatively long life-time ...at moderate densities ct 10-15 fm/c In-medium invariant mass reconstruction combinatorial background reduction

  4. ,g w p0 e+ e- ,p0 g N* e+ e- e+ e- g* w/r/f Invariant mass spectrum decomposition Elementary processes: • Meson Dalitz decays: • Baryon Dalitza decays: • Two-body decays: Example cocktail (DLS data compared to HSD model)

  5. The DLS results • The shape (0.05  M  0.35) can be explained by Dalitz decays of p0 and h if cross sections are scaled appropriately – but in contradiction with TAPS measurement... Calculation: K. Shekhter, C. Fuchs et al. (Tübingen) Phys. Rev. C68(2003) 014904 Done using strong or weak (s/w) r - N*(1535) coupling Data: R.J. Porter et al.: PRL 79 (1997) 1229 BUU model: E.L. Bratkovskaya et al.: NP A634 (1998) 168,in-medium spectral functions  DLS puzzle!

  6. HADES … What and where?...

  7. High Acceptance Di-Electron Spectrometer • Installed at the SIS18, GSI Darmstadt • Spectrometer with high invariant mass resolution and high rate capability • Utilizes dedicated second level trigger processors to select rare events before mass storing • Beams of: • Pions • Protons • Nuclei • Geometry • Full azimuth, polar angles 18 - 85 (y = 0 – 2) • Pair acceptance  0.35 • ~ 80.000 channels, seg. solid or LH2 targets

  8. HADES Spectrometer Side View START Fast particle identification Momentum measurement • Magnet: superconducting toroid: Br = 0.36 Tm TOF: 384 scintil. rods , s 150 ps TOFino: 24 scintil. paddles, s 450 ps temporary solution, RPC in future Pre-Shower: 18 pad chambers & 12 lead converters between RICH: CsI solid photo cathode, C4F10 radiator, N0 8090, p - suppression: 104 MDC: 24 multiwire drift chambers, sy 100 mm single cell resolution 1 m

  9. Experimental (production) runs • November 2002:C+C 2 AGeV, commissioning and physics runs • target= 2 x 2.5% 650 Mevents • 6 outer drift chambers (MDC) in 4 sectors • February 2004: p+p 2GeV • target 5 cm LH2, almost full spectrometer setup600 Mevents • August 2004:C+C 1AGeV • 3x2 % target 2500 Mevents • September 2005:Ar+KCl 1.75 AGeV • 4x1.5 % target 1200 Mevents • May 2006:p+p 1.25 GeV • Target 5 cm LH23000 Mevents

  10. hadron : lepton suppression 10000 : 1 Minv = e- e+ log. z axis ! p1 e+ q RICH p2 e- Target Analysis strategy • Single electron analysis • Classical: 2-dim cuts on RICH rings, Shower, p vs b, hit matching ... • or: Bayes theorem: cut on pid prob. • track fitting quality • e+e- pair analysis • close pair cuts • opening angle q > 9° (tracks removed) • Corrections for detectorand reconstruction efficiencies acceptance & reconstruction efficiency filters available

  11. Combinatorial background (CB): • from like-sign pairs • CB = • Signal:S+=Ne+eCB+ C+C @ 2 AGeV - mass spectrum limited resoultion ( ~DLS level )only inner MDC chambers in 2002 ( picture above )no acceptance / efficiency corrections signal < 140 MeV/c2: 20971 counts signal > 140 MeV/c2: 1937 counts

  12. red bars – stat+syst err • syst. error (~30%): • uncertainty in normalization • reconstruction efficiency corr. • CB construction average number of participating nucleons Apart = 8.6 extrapolated charged pion yield N4 / Apart = 0.135  0.015 C+C @ 2 AGeV - mass spectrum corrected • Efficiency corrected spectra • - detector efficiency • - reconstruction efficiency •  normalized to the pion yield in HADES acceptance 12C+12C 2AGeV PLUTO event gener. (HADES Collaboration) 0and  well known (thermal freezout) based on TAPS measurements

  13. C+C @ 2 AGeV – HSD model vacuum in-medium ( data described quite well )

  14. C+C @ 2 AGeV – UrQMD model Transport calculation (vacuum result) UrQMD Frankfurt M. Bleicher, D. Schumacher problems in the high mass region

  15. C+C @ 2 AGeV – RQMD model RQMD Tübingen D. Cozma, C. Fuchs • subthreshold / production (via resonances) • eVMD model • in-medium: collisional broadening decoherence In-medium: problems in the intermediate mass region

  16. C+C @ 2 AGeV - comparison with models • experimental data • efficiency corrected • pair cut 12 = 9theor. models • vacuum calculations • Included calculations: • RQMD TübingenD. Cozma, C. Fuchs • UrQMD Frankfurt • M. Bleicher, D. Schumacher • HSD Gießen (v2.5) • E. Bratkovskaya, W. Cassing • Included calculations: • PLUTO evt generator • HADES collaboration • UrQMD Frankfurt • M. Bleicher, D. Schumacher • HSD Gießen (v2.5) • E. Bratkovskaya, W. Cassing

  17. HSD solid line vacuum dashed line in-medium PLUTO – dashedHSD– solid C+C @ 2 AGeV – rapidity – exp, PLUTO, HSD dots - experiment dashed line - PLUTO solid line - HSD discrepancy in medium (PLUTO, HSD) and high mass (PLUTO) region

  18. C+C @ 2 AGeV – pT – exp, PLUTO, HSD PLUTO discrepancy in medium and high mass region HSD solid line vacuum dashed line in-medium

  19. C+C @ 1 AGeV - preliminary • Comb. backgr. (CB): from like-sign pairs CB =S+= Ne+eCB+ not efficiency corrected ! Normalized to π0 70% of the full data statistics preliminary Direct comparison to DLS data possible • Exp. Data: • no efficiency correction • PLUTO: • filtered with HADES • acceptance * efficiency only π0 , η isnot sufficient to describe the data – model comparison in the future

  20. Summary • HADES fully operational – 1 month experimental runs • 12C + 12C 2 AGeV analyzed (PRL paper submitted soon) • di-electron spectrum efficiency corrected • systematic errors estimated (based on simulation) • 0 in agreement with TAPS / KAOS measurement • comparison with transport models • vacuum results failed to describe high mass region • 12C + 12C 1 AGeV preliminary • 5x higher data statistics – analysis on-going • direct comparison to DLS data possible • A lot of physics ahead for the coming years • 40Ar+39K37Cl @ 1.75 AGeV analysis started soon • elementary reactions: p+p @ 2.2 GeV, 1.25 GeV, 3.5 GeV • high momentum resolution achieved (σ = 3.5%) •  form factor measurement feasible •  in nucleus production • p, p, heavy ion: high precision in-medium spectroscopy

  21. HADES collaboration G.Agakishiev7, C.Agodi2, H.Alvarez-Pol19, A.Balanda5, R.Bassini10, G.Bellia2,3, D.Belver19, J.Bielcik6, A.Blanco4, M.Böhmer14, C.Boiano10, A.Bortolotti10, J.Boyard16, S.Brambilla10, P.Braun-Munzinger6, P.Cabanelas19, S.Chernenko7, T.Christ14, R.Coniglione2, M.Dahlinger6, J.Díaz20, R.Djeridi9, F.Dohrmann18, I.Durán19, T.Eberl14, W.Enghardt18, L.Fabbietti14, O.Fateev7, P.Finocchiaro2, P.Fonte4, J.Friese14, I.Fröhlich9, J.Garzón19, R.Gernhäuser14, M.Golubeva12, D.González-Díaz19, E.Grosse18, F.Guber12, T.Heinz6, T.Hennino16, S.Hlavac1, J.Hoffmann6, R.Holzmann6, A.Ierusalimov7, I.Iori10,11, Ivashkin12, M.Jaskula5, M.Jurkovic14, M.Kajetanowicz5, B.Kämpfer18, K.Kanaki18, T.Karavicheva12, D.Kirschner9, I.Koenig6, W.Koenig6, B.Kolb6, U.Kopf6, R.Kotte18, J.Kotulic-Bunta1, R.Krücken14, A.Kugler17, W.Kühn9, R.Kulessa5, S.Lang6, J.Lehnert9, L.Maier14, P.Maier-Komor14, C.Maiolino2, J.Marín19, J.Markert8, V.Metag9, N.Montes19, E.Moriniere16, J.Mousa15, M.Münch6, C.Müntz8, L.Naumann18, R.Novotny9, J.Novotny17, W.Ott6, J.Otwinowski5, Y.Pachmayer8, V.Pechenov7, T.Pérez9, J.Pietraszko6, J.Pinhao4, R.Pleskac17, V.Pospísil17, W.Przygoda5, A.Pullia10,11, N.Rabin13, B.Ramstein16, S.Riboldi10, J.Ritman9, P.Rosier16, M.Roy-Stephan16, A.Rustamov6, A.Sadovsky18, B.Sailer14, P.Salabura5, P.Sapienza2, A.Schmah6, W.Schön6, C.Schroeder6, E.Schwab6, P.Senger6, R.Simon6, V.Smolyankin13, L.Smykov7, S.Spataro2, B.Spruck9, H.Stroebele8, J.Stroth8,6, C.Sturm6, M.Sudol8,6, V.Tiflov12, P.Tlusty17, A.Toia9, M.Traxler6, H.Tsertos15, I.Turzo1, V.Wagner17, W.Walus5, C.Willmott19, S.Winkler14, M.Wisniowski5, T.Wojcik5, J.Wüstenfeld8, Y.Zanevsky7, P.Zumbruch6 1)Institute of Physics, Slovak Academy of Sciences, 84228 Bratislava, Slovakia 2)Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud, 95125 Catania, Italy 3)Dipartimento di Fisica e Astronomia, Università di Catania, 95125, Catania, Italy 4)LIP-Laboratório de Instrumentação e Física Experimental de Partículas, Departamento de Física da Universidade de Coimbra, 3004-516 Coimbra, Portugal 5)Smoluchowski Institute of Physics, Jagiellonian University of Cracow, 30059 Cracow, Poland 6)Gesellschaft für Schwerionenforschung mbH, 64291 Darmstadt, Germany 7)Joint Institute of Nuclear Research, 141980 Dubna, Russia 8)Institut für Kernphysik, Johann Wolfgang Goethe-Universität, 60486 Frankfurt, Germany 9)II.Physikalisches Institut, Justus Liebig Universität Giessen, 35392 Giessen, Germany 10)Istituto Nazionale di Fisica Nucleare, Sezione di Milano, 20133 Milano, Italy 11)Dipartimento di Fisica, Università di Milano, 20133 Milano, Italy 12)Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow, Russia 13)Institute of Theoretical and Experimental Physics, 117218 Moscow, Russia 14)Physik Department E12, Technische Universität München, 85748 Garching, Germany 15)Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus 16)Institut de Physique Nucléaire d'Orsay, CNRS/IN2P3, 91406 Orsay Cedex, France 17)Nuclear Physics Institute, Academy of Sciences of Czech Republic, 25068 Rez, Czech Republic 18)Institut für Kern- und Hadronenphysik, Forschungszentrum Rossendorf, PF 510119, 01314 Dresden, Germany 19)Departamento de Física de Partículas. University of Santiago de Compostela. 15782 Santiago de Compostela, Spain 20)Instituto de Física Corpuscular, Universidad de Valencia-CSIC,46971-Valencia, Spain

More Related