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HADES experiments at GSI .

N.  . R. e +. . e -. HADES experiments at GSI . Electromagnetic structure of Time-Like baryonic transitions in pion induced reactions. B. Ramstein , IPN Orsay ECT, Trento, 20/05/2013. Outline. Introduction: General context of HADES experiments

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HADES experiments at GSI .

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  1. N  R e+  e- HADES experiments at GSI. Electromagnetic structure of Time-Like baryonic transitions in pion induced reactions B. Ramstein, IPN Orsay ECT, Trento, 20/05/2013 B. Ramstein

  2. Outline • Introduction: • General context of HADES experiments • In-medium modifications of vectormesons • Link to Time-Like elctromagnetic structure of baryonic transitions • Resultsfrom pp reactionswithHADES • Sensitivity to Time-Likeelectromagnetic structure of baryonic transitions • Perspectives of HADES measurementswith the GSI pion beam (2014) • -p ne+e-below ω threshold • Time-Like electromagnetic transition form factors • -p -p, -p -+n, -p -0p and kaon production • PWA  baryonic resonance parameters • Conclusions B. Ramstein

  3. QGP SPS Na60 HADES SIS-100 SIS-300 CBM RHIC AGS hadrons SIS-18 KEK,JLAB,TAPS G7 Motivations of the HADES experiment Exploring the phase diagram of hadronic matter….. • E/A=1-2 AGeV • /o ~ 1-3, T < 100 MeV • N/Apart ≈ 10% CERES LHC ….. using dilepton emission: rare but undistorted probe DLS DLS e+ e- B. Ramstein

  4. In-medium vectormeson modifications: B. Ramstein N*   + ... N-1 seee.g. Leupold ,Metag,MoselInt. J. of Mod. Phys. E19 (2010) 147 for a recentreview « in-medium broadening » In-medium spectral function depends on  NN* coupling Rapp and Wambach EPJA 6 (1999) 415 Rapp, Chanfray and Wambach NPA 617, (1997) 472 4

  5. The  meson in hot and dense hadronic matter from SIS18 to SPS Source of  mesons Source of  mesons at 1-2 AGeV NN NR NN N R N  Source of  mesons Source of  mesons at ultra relativistic energies +-  Depends on RN coupling Coupling of ρ to baryonic resonances can be studied in NN and N collisions at 1-2 GeV

  6. g* g* e+ r, w, e+ e- e- Relation to electromagnetic structure of baryons ρ meson production and decay Dalitz decay of baryonic resonances RNe+e- R R N electromagnetic elastic or transition formfactors N Vector Meson Dominance Model Coupling constants q2=M2inv(e+e-)=M2* >0 q2  0 : « Time like «  region electromagnetic form factors are unknown ! B. Ramstein

  7. Baryonic transition electromagneticformfactors in space-Likeregion Baryonic electromagnetic form factors are measured for q20 e+ e- D+ * Magnetic form factor for γ*p(1232) q2=M2* <0 Data: Mainz, Jlab I.G. Aznauryan, V.D. Burkert Prog. Part. Nucl. Phys. 67, 1 (2012) p Helicity amplitudes for γ*pN(1520) D13 compared to quark models No measurement at q2> 0  use models fitted on space like data B. Ramstein

  8. B’ B’ B B V= , ,  0.6m2 GMN-/3GD GN-M(q2) Two-component quark model • unified description of baryonicformfactors • analyticalderivation of form factor startingfromwavefunctions • N- transition: 4 parametersfitted on • elasticnucleon FF (SL+TL) • SL N- transition GM • analytical continuation to Time-Likeregion Iachello & Wan ,Phys. Rev. C 69, 055204 (2004) Wan & Iachello, int. J. Mod. Phys. A20(2005) 1846 Emilie Moriniere PHD, Orsay F. Dorhmann et al , EPJA 45,401(2001) Time-like Space-like B. Ramstein

  9. B. Ramstein Barequark+mesoncloud model for N- transition emform factor G.Ramalho and T. Pena Phys. ReV. D85,113014 (2012) Coupling to the bare quarks Coupling to the mesoncloud Bare quark contributiion m2 0.6m2 Full model SpaceLike Time Like • Extension to Time-Like region • exists for elastic nucleon • form factors • ( to be measured with PANDA) • In progress for higher resonances

  10. Hades « strategy» : 2013 status B. Ramstein • Studydileptonemission in dense and hot matter(cf.DLS/Berkeley) • A+A reactions in the 1-2 AGeVenergy range • C+C, Ar+KCl, Au+Au (2012) • cold matterat normal nucleardensity p+Nb 3.5 GeV (cf KEK, Jlab, CBELSA/TAPS) • Elementary collisions pp, dpand in future -p • reference to heavy-ion spectra • understanddilepton production mechanism (exclusive channels) • dileptonemissionisprobingtime-likeelectromagnetic structure of hadronic transitions! • Simultaneousmeasurements of hadronicchannels (pp NN, pp NN) • Cross-checks on knownchannels, detailed information on baryonicresonance production • …. strangenessmeasurement program: K- , K0,, (1385), (1405) to be • investigatedalso in -p and -A

  11. B. Ramstein The Collaboration 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 • München (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 GSI IPN Orsay, 17/10/2011 11 Béatrice Ramstein

  12. B. Ramstein HADES 2nd generation dilepton spectrometer Side View START Acceptance:Full azimuth, polar angles 18o - 85o Pair acceptance  0.35 Particle identification: RICH,Time Of Flight, Pre-Shower (pad chambers & lead converter) ( also MDC (K)) Trigger: 1st Level: charged particle multiplicity (~10 kHz) 2nd Level: single electron trigger (~2.5 kHz) Momentum measurement Magnet: ∫Bdl = 0.1- 0.34 Tm MDC: 24 Mini Drift Chambers Leptons: x~ 140  per cell, p/p ~ 1-2 % M/M ~ 2% at  peak Upgrade (2010) • New DAQ ~20 kHz • new MDCs for plane 1 • RPC θ <45° FW  < 7° 12

  13. Sensitivity to Time-Like Electromagnetic transitions in pp reactions ppppe+e- 1.25 GeV resonance Dalitz decay 2.2 and 3.5 GeV higher lying resonances

  14. Dilepton production in pp reaction at 1.25 GeV 0.6m2 • below  threshold • only 2 dilepton sources HADES: Phys.Lett.B690 (2010)118 • ° Dalitzdecay° =4.5 mb • branching ratio ° → e+e- 1.2 % • Dalitzdecay: • branching ratio  → Ne+e- (QED :4.2 10-5) • non resonant contribution expected to besmall GM(q2) • Time-like N-  transition electromagnetic • formfactors • Resonance model results: • ° Dalitz • Dalitz)+ effect of Iachello FF Wan and Iachello Int. J Mod. Phys. A20 (2005) 1846 G. Ramalho and T. Pena arxiv: 1205.2575v1 (2012) Béatrice Ramstein

  15. e-  * e+  preliminary p p 1 p2 N D+ p e+ q2=M2inv(e+e-)=M2* e- (p,e+,e-) invariant mass(GeV/c2) preliminary cos(CMpe+e-) Exclusive analysis : ppppe+e-at 1.25 GeVusingpe+e-events Good agreement with simulation of  production + Dalitzdecay (cfhadronicchannels) • Exclusive channels confirm the dominance of  Dalitz decay • First measurement of  Dalitzdecay! • Dalitzdecaybranching ratio in agreement withQED value (4.2 10 -5) acceptancecorrected Helicity distributions *  e+e- d/dΩe~ 1+cos2 In HADES acceptance W. Przygoda’s analysis Cracow cos

  16. p p → e+ e- π0 p d → e+ e- π0 n | | Half-off-shellelectromagneticnucleonformfactors In the unphysical region (cf PANDA ) Non-resonant contributions in NNNNe+e- OBE models R. Shyam & U. Mosel, PRC 79 (2009) 03520 L.P. Kaptari, B. Kämpfer, NPA 764 (2006) 338 HADES data: Phys.Lett.B690 (2010)118 meson exchange currents Pion form factor n N p n p N • sensitivityto hadronicelectromagneticstructure • much better agreement with data with  em form factor ! with  em FF On-goinganalysis: • pionicchannels • exclusive pnpne+e- B. Ramstein

  17. ppe+e-X E=2.2 GeV,3.5 GeV Comparison to cocktail of dilepton sources • Direct production of / • Dalitz decay of  resonance (point-like) E=2.2 GeV E=3.5 GeV Hades collab., EPJA48 (2012) 64 Hades collab., PRC85 054005 (2012) Effect of electromagnetic form factors / Coupling of  to baryonic resonances ? B. Ramstein

  18. Exclusive ppppe+e-channel at 3.5 GeV • Cross sections and angular distributions for baryonic resonances from hadronic channel analysis • Direct production of ,, with cross sections from hadronic analysis (of /+-0) and =1/2 • Constant form factors ( taken atq2=0) M. Zetenyi and G. Wolf Heavy Ion Phys. 17 (2003) 27 ppe+ e- preliminary ppe+ e- R ω  ω R ρ A. Dybczak, Cracow  Additional information from exclusive channels Missing yield related to light baryonic resonances (N(1520) ,..)

  19. Transport model calculations for inclusive e+e- production in pp “ electromagnetic form factor approach”: “ρ production approach”: NR couplings VDM pp 3.5 GeV Hades data, Eur.Phys.J. A48 (2012) 64 Courtesy of Janus Weil N- Form Factor: G.Ramalhoand T. Pena Phys. ReV. D85,113014 (2012) •  mass distribution stronglymodified in NN collisions • Sameorigin as in-medium effects • (coupling to baryonicresonances) • large uncertainties: production • cross sections of baryonic resonances, ρNN* couplings   beam experiment ρ N*/ N(1620)   N(1520) N(1720) N-1 B. Ramstein J. Weil, H. van Hees and U. Mosel, EPJA 48, 111 (2012)

  20. Project of pion beam experiments with HADES pion momentum0.6 < p <1.5 GeV/c I ~ 106/s s 1.21 1.52 1.68 η ω B. Ramstein B. Ramstein 20

  21. Pion beamexperimentswith HADES: an « old » idea • Belongs since the very beginning to the HADES experimental program • Dileptonspectroscopy in  inducedexperiments • +A • Cold nuclearmatterstudies, medium effects on /ωmesons • +N • Reference for +A studies, • Exclusive channels- p  n e+e- studies of ρ/ωproduction • Specialinterest of subthreshold production (coupling to baryonicresonances) Strangeness production (K+,K-,K0S,ϕ) in +A Below threshold • One pion, two pions and kaon production from an energy scan in -p reactions HADES 2013 program with pion beams Based on HADES results Constraints of beam time at GSI B. Ramstein

  22. B. Ramstein N R  e+  e- Motivations of N experimentswithHADES: Dilepton channels • well-known production mechanism • fixedresonance mass MR=sqrt(s) • exclusive- p  n e+e- channels( contribution canberejected ) Time-Like electromagnetic form factors Space-Like electromagnetic form factors n - q2 <0 fixed e+ R Inverse pion electroproduction * e+ p * R q2 > 0 variable e- e- p - e-- p studied at JLab/CLAS Vector Dominance Model /coupling N(1520) r r More direct access to Time-Likeem transition formfactorsthan in pp + ... N-1 22

  23. / production in N reactions • B. Kaempfer , A Titov , R.Reznik Nucl. Phys. A721(2003)583 • Titov, B.KaempferEPJA 12(2001)217 M.F.M. Lutz , B. Friman, M. Sayuer Nuclear Physics A 713 (2003) 97–118 N(1535) hadronic coupled channel models fitted to γpρ/ω p and -pρ/ω n data quark models or derived from Branching ratios N(1680) Coupling constants N R -pρn e+ smaller amplitudes D13(1520) has a larger contribution ρ/ω e- N(1440) • Common result: • sensitivity of subthreshold production • to coupling to baryonicresonances • important interferenceeffects • expectedbetween I=0 (ω) • and I=1 (ρ) channels Mee=0.6 GeV/c2 -pωn N(1535) N(1440) N(1680) N(1675) B. Ramstein, IPN Orsay

  24. N R  e+ e- / interference: different models • Titov, B.KaempferEPJA 12(2001)217 M.F.M. Lutz , B. Friman, M. Sayuer Nuclear Physics A 713 (2003) 97–118 γ* angular distributions in CM sensitive to res.contributions Almost total cancellation of ρ and ω amplitudes ! Data (ee invariant mass and angular distributions) needed to fix coupling of baryonic resonances to ρ/ω mesons B. Ramstein, IPN Orsay

  25. Electromagnetic form factors approach • M. Zetenyi and G. Wolf, Phys.Rev. C86 (2012) 065209 • ρ production is embedded in the em form factor R R u channel schannel + Born term + ρ meson exchange • adjustmentto pion photoproduction cross sections of • RN couplings (within the range allowed by the radiative decaywidths) γp+n • Further studies needed: • Inclusion of ω contribution • Too large cross sections for • ρ production π-pne+e- B. Ramstein

  26. N R  e+ e- Simulations using the resonance model H.Kuc (Orsay/Cracow) Dalitz decays Form factors: « photon-point » M. Zetenyi, Gy. Wolf, nucl-th0202047 Missing mass selection aftermissing mass cut -pe+e- n p=0.8 GeV/c s=1.55 GeV/c Missing mass (GeV/c) Mee(GeV/c2) B. Ramstein Mee (GeV/c2)

  27. N R  e+ e- π-pne+e-: count rate estimates P=0.8 GeV/c (below  threshold) H.Kuc Resonance model incoherent sum (M. Soyeur) Coherent sum (M. Soyeur) π-pne+e- with HADES Measurement of e+e- invariant mass spectra and angular distributions (cf results from pp reactions)  unique chance for a direct access to Time-like electromagnetic form factors M.F.M. Lutz , B. Friman, M. Soyeur Nuclear Physics A 713 (2003) 97–118

  28. πNππN: present status • All what we know about N* couplings to ρN, π, N is due to • Manley, Arndt, Goradia, Teplitz PRD 30 (1984) 904. • based on the analysis of 240000 events (bubble chamber < 1980) • Complete existing very precise photoproductiondata • Improve knowledge of baryonic resonances, MR, (N*Nπ), (N*Nππ) • Dynamical models are now available  a new combined PWA analysis of all pion and photoproduction channels will be possible. • Important for baryonic structure issues (Constituent Quark Models, Lattice QCD) B. Ramstein

  29. Some open issues for πNππN and πNπN measurements N(1520) D13 state Manley et al. strong N(1520)2 BR(ρN)~20% Branching ratios to πΔ and (π π)sN need to bechecked N(1440)P11 Coupled channel Giessen / Manley • Existence contradictory • Not seen in the latest PWA analysis • BR(2π) =40 to 90 % (PDG 2010) N(1710)P11 • Important coupled channel effects • With BR(ρN)~20%, cross sections • are not reproduced • need for differential cross sections • Important for medium effects N(1520)   N-1

  30. acceptancep/p =8% Momentummeasurementneeded X,Y det2 Trigger on interactions with the target, halo rejection X,Y det1 in beam, position sensitive detectors • optimization of pion production yield (duty cycle, primarybeamintensity) • optimization of beam line acceptance and extension at the target B. Ramstein

  31. B. Ramstein Pion Beam tracking Beam line optimization: Orsay p/p~0,1-0.3 % x<1mm L. Fabbietti’s group. Excellence Cluster Universe, Garching 10x10 cm2 2x128 channels 300  Si detector Diamond start detector GSI

  32. Conclusion: • perspectives of pion beamexperimentswith HADES ( 2014) • Strangeness production in -A at 1.7 GeV/c • -pne+e- at 0.8 GeV/c • Elementary reactions are very important tocontrol the interpretation of • medium effects(lesson from HADES dilepton experimental program ) • Unique chance to studyTime-Likeelectromagnetic structure of higherlyingresonances/coupling to ρ/ω mesons(complementary to pion electroproduction) • Energy scan of -p reactions : one pion, twopion and kaon production • Urgent need of new data for Partial WaveAnalysis baryonicresonanceproperties GSI pion beamis unique in world atpresent to providethese data This should be exploited ,…. before HADES moves to FAIR 32 Béatrice Ramstein

  33. B. Ramstein Thank you

  34. B. Ramstein Simulations for dilepton production below  threshold Simple resonance model: Dalitzdecay of differentbaryonicresonanceswith constant formfactors + meson contribution Efects of electromagnetic form factors ? Important interference effects expected between I=0 (ω) and I=1 (ρ) channels Linked to coupling to baryonic resonances H. KucPhD Orsay/Cracovie after missing mass cut -pe+e- n P=0.8 GeV/c Calculationsbased on hadronic couplings M. Lutz, B. Friman, M. Soyeur, NPA 713 (2003) 9 Titov and Kämpfer EPJA 12 (2001) 217 Very new calculationbased on VDM transition formfactorsby Zetenyi and WolfarXiv:1208.5671v1 [nucl-th] Mee(GeV/c2) 34

  35. B. Ramstein

  36. two component model: fit of parameters to existing data elastic nucleon form factors 4 parameters a2, , g8 ,v N- magnetic transition form factors 2 additionnal parameters: a’,g10 best fit a’/a= 1.27 g10/g8=1.28 GMN-/3GD GMp/pFd GEp /Fd GMp Time-Like GMn /nFd GEn B. Ramstein

  37. B. Ramstein Towards a consistent description of dilepton production in all systems Confirmation of DLS data ! HSD: E. Bratkovskaya et al. arXiv:1301.0786 [ predictions • pp also rather well described, problem remains with pn data • Still contradictory predictions (UrQMD) • modifications of spectral functions are small at SIS energies (except Au+Au ?) • But HADES data are useful to study the ρN(N*/) couplings (which are crucial for medium effects) and are very efficient in putting constraints to models

  38. Technical layout of HADES TOF Cryostat Pre-Shower outer MDC outer MDC RPC B field region inner MDC He pipe beam Start + target HADES cave HADES sector inner MDC RICH readout 38 B. Ramstein Lecture III: 38

  39. Studying cold nuclear matter in p+Nb at 3.5 GeV G. Agakishiev et al., Phys.Lett. B715 (2012) 304-309 First measurement of lepton pairs with pe+e- < 0.8 GeV/c radiated from cold matter ( not measured by CLAS, KEK-E325) • ω not modifed, but absorbed • clear excess in p+A below vector meson pole  • - secondary reactions +N  (1720,..)(N* (1520),..) NρNe+e- • - Electromagnetic Time-Like form factors ? B. Ramstein

  40. E. Bratkovskaya (Frankfurt)New HSD calculations • emphasizes interest of subthreshold production (via N(1520) resonance) • Medium effects are predicted • accounting of the in-medium effects - a collisional broadening and dropping mass of the vector mesons (r,w,f) – leads to changes of the final spectra: • reduction of the r,w,f peaks • enhancement of the dilepton yield for 0.4<M<0.7 GeV • effect is stronger for heavy nuclei HSD: preliminary HSD’09 => similar to W. Cassing, Y.S. Golubeva, A.S. Iljinov, L.A. Kondratyuk, Phys. Lett. B 396 (1997) 26 Sesimbra, May 2009

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