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

2. Outline  Introduction: General context of HADES experiments In-medium modifications of vector mesons Link to Time-Like elctromagnetic structure of baryonic transitions Results from pp reactions with HADES Sensitivity to Time-Like electromagnetic structure of baryonic transitions  Perspectives of HADES measurements with the GSI pion beam (2014)  - p  ne + e - below ω threshold Time-Like electromagnetic transition form factors  - p  - p,  - p  -  + n,  - p  -  0 p and kaon production PWA  baryonic resonance parameters  Conclusions 2 Trento, 20/05/2013 B. Ramstein

3. 3 Exploring the phase diagram of hadronic matter….. hadronic matter….. Motivations of the HADES experiment E/A=1-2 AGeV   /  o ~ 1-3, T < 100 MeV  N  /A part ≈ 10% ….. using dilepton emission: rare but undistorted probe Trento, 22/02/2013 B. Ramstein e+ e-e- CERES AGS SPS RHIC QGP hadrons SIS-100 SIS-300 SIS-18 CBM G7 HADES KEK,JLAB,TAPS Na60 DLS LHC

4. 4 In-medium vector meson modifications: see e.g. Leupold,Metag,Mosel Int. J. of Mod. Phys. E19 (2010) 147 for a recent review   N -1 N* +... Rapp and Wambach EPJA 6 (1999) 415 Rapp, Chanfray and Wambach NPA 617, (1997) 472 « in-medium broadening » In-medium spectral function depends on  NN* coupling Trento, 20/05/2013 B. Ramstein

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

6. Relation to electromagnetic structure of baryons electromagnetic elastic or transition form factors  e+e+ e-e-  e+e+ e-e-  Coupling constants R N R N 6 Dalitz decay of baryonic resonances R  Ne + e - ρ meson production and decay Trento, 20/05/2013 B. Ramstein Vector Meson Dominance Model q 2  0 : « Time like « region electromagnetic form factors are unknown ! q 2 =M 2 inv (e + e - )=M 2  * >0

7. Trento, 20/05/2013 B. Ramstein 7 Baryonic electromagnetic form factors are measured for q 2  0 Data: Mainz, Jlab I.G. Aznauryan, V.D. Burkert Prog. Part. Nucl. Phys. 67, 1 (2012) Helicity amplitudes for γ*p  N(1520) D 13 compared to quark models Magnetic form factor for γ*p  (1232) Baryonic transition electromagnetic form factors in space- Like region No measurement at q 2 > 0  use models fitted on space like data ++ p e+e+ e-e- ** q 2 =M 2  * <0

8. G M N-  /3G D Two-component quark model B. Ramstein 8 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 ) Space-like V= , ,  BB B’ unified description of baryonic form factors analytical derivation of form factor starting from wave functions N-  transition: 4 parameters fitted on  elastic nucleon FF (SL+TL)  SL N-  transition G M analytical continuation to Time-Like region 0.6m  2 G N-  M (q 2 ) Time-like Trento, 20/05/2013

9. 9 Bare quark+meson cloud model for N-  transition em form factor Space Like Time Like 0.6m 2  Coupling to the bare quarks m2m2 Coupling to the meson cloud G.Ramalho and T. Pena Phys. ReV. D85,113014 (2012) B. Ramstein Bare quark contributiion Full model Extension to Time-Like region exists for elastic nucleon form factors ( to be measured with PANDA) In progress for higher resonances Trento, 20/05/2013

10. Hades « strategy » : 2013 status Study dilepton emission in dense and hot matter (cf. DLS/Berkeley) Study dilepton emission in dense and hot matter (cf. DLS/Berkeley) A+A reactions in the 1-2 AGeV energy range A+A reactions in the 1-2 AGeV energy range C+C, Ar+KCl, Au+Au (2012) C+C, Ar+KCl, Au+Au (2012) cold matter at normal nuclear density p+Nb 3.5 GeV cold matter at normal nuclear density p+Nb 3.5 GeV (cf KEK, Jlab, CBELSA/TAPS) (cf KEK, Jlab, CBELSA/TAPS) Elementary collisions pp, dp and in future  - p Elementary collisions pp, dp and in future  - p reference to heavy-ion spectra reference to heavy-ion spectra understand dilepton production mechanism (exclusive channels) understand dilepton production mechanism (exclusive channels) dilepton emission is probing time-like electromagnetic structure of hadronic transitions! dilepton emission is probing time-like electromagnetic structure of hadronic transitions! Simultaneous measurements of hadronic channels (pp  NN , pp  NN  ) Simultaneous measurements of hadronic channels (pp  NN , pp  NN  ) Cross-checks on known channels, detailed information on baryonic resonance production Cross-checks on known channels, detailed information on baryonic resonance production …. strangeness measurement program: K -, K 0, ,  (1385),  (1405) to be …. strangeness measurement program: K -, K 0, ,  (1385),  (1405) to be investigated also in  - p and  - A investigated also in  - p and  - A 10 Trento, 20/05/2013 B. Ramstein

11. IPN Orsay, 17/10/2011 Béatrice Ramstein 11 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  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 11 Trento, 20/05/2013 B. Ramstein

12. Side View START 12 FW Acceptance: Full azimuth, polar angles 18 o - 85 o 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 HADES 2 nd generation dilepton spectrometer  < 7° Upgrade (2010) New DAQ ~20 kHz new MDCs for plane 1 RPC θ <45° Trento, 20/05/2013 B. Ramstein

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 pp  ppe + e - 1.25 GeV  resonance Dalitz decay 2.2 and 3.5 GeV higher lying resonances

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

15. Exclusive analysis : pp  ppe + e - at 1.25 GeV using pe + e - events pp pp e+e+ ++ p q 2 =M 2 inv (e + e - )=M 2  * 1 e-e- Good agreement with simulation of  production + Dalitz decay (cf hadronic channels) preliminary (p,e +,e - ) invariant mass (GeV/c 2 ) cos(  CM pe+e- ) preliminary In HADES acceptance acceptance corrected   ** N e+e+ e-e- cos  Helicity distributions  *  e + e - d  /dΩ e ~ 1+cos 2  d  /dΩ e ~ 1+cos 2   Exclusive channels confirm the dominance of  Dalitz decay  First measurement of  Dalitz decay! Dalitz decay branching ratio in agreement with QED value (4.2 10 -5 ) W. Przygoda’s analysis Cracow 15Trento, 20/05/2013

16. 16 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 meson exchange currents N N p n n p B. Ramstein with  em FF sensitivity to hadronic electromagnetic structure much better agreement with data with  em form factor ! On-going analysis:  pionic channels  exclusive pn  pne + e - HADES data: Phys.Lett.B690 (2010)118 Pion form factor Half-off-shell electromagnetic nucleon form factors In the unphysical region (cf PANDA ) p p → e + e - π 0 | p d → e + e - π 0 n |

17. pp  e + e - X E=2.2 GeV,3.5 GeV E=2.2 GeV E=3.5 GeV Comparison to cocktail of dilepton sources Direct production of  /  Dalitz decay of  resonance (point-like) Effect of electromagnetic form factors / Coupling of  to baryonic resonances ? Hades collab., PRC85 054005 (2012) Hades collab., EPJA48 (2012) 64 17Trento, 20/05/2013 B. Ramstein

18. ppe+ e- 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     Constant form factors  taken at  q 2 =0) M. Zetenyi and G. Wolf Heavy Ion Phys. 17 (2003) 27 A. Dybczak, Cracow Additional information from exclusive channels Missing yield related to light baryonic resonances (N(1520),..)  R ρ ω R ω  preliminary ppe+ e-

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

20. Project of pion beam experiments with HADES Trento, 20/05/2013 B. Ramstein 20 B. Ramstein 20 pion momentum 0.6 < p <1.5 GeV/c I ~ 10 6 /s 1.211.521.68 ss ω η

21. Pion beam experiments with HADES: an « old » idea Trento, 20/05/2013 B. Ramstein 21 Belongs since the very beginning to the HADES experimental program Dilepton spectroscopy in  induced experiments  +A Cold nuclear matter studies, medium effects on  / ω mesons  +N Reference for  +A studies, Exclusive channels  - p  n e + e - studies of ρ/ω production Special interest of subthreshold production (coupling to baryonic resonances) Strangeness production (K +,K -,K 0 S, ϕ ) in  +A HADES 2013 program with pion beams Based on HADES results Constraints of beam time at GSI HADES 2013 program with pion beams Based on HADES results Constraints of beam time at GSI Below threshold One pion, two pions and kaon production from an energy scan in  - p reactions

22. 22  well-known production mechanism  fixed resonance mass M R =sqrt(s)  exclusive  - p  n e + e - channels  exclusive  - p  n e + e - channels (  contribution can be rejected ) Motivations of  N experiments with HADES: Motivations of  N experiments with HADES: Dilepton channels Dilepton channels Time-Like electromagnetic form factors e+e+ n e -- **  - - More direct access to Time-Like em transition form factors than in pp R q 2 > 0 variable p e+e+ e-e- e-e- ** -- R p Space-Like electromagnetic form factors q 2 <0 fixed studied at JLab/CLAS Vector Dominance Model   /  coupling  e+e+ e-e-  R N Inverse pion electroproduction   N -1 N(1520) +... Trento, 20/05/2013 B. Ramstein p

23. B. Ramstein, IPN Orsay 23  /  production in  N reactions M.F.M. Lutz, B. Friman, M. Sayuer Nuclear Physics A 713 (2003) 97–118 B. Kaempfer, A Titov, R.Reznik Nucl. Phys. A721(2003)583 A.Titov, B.Kaempfer EPJA 12(2001)217 smaller amplitudes D 13 (1520) has a larger contribution quark models or derived from Branching ratios Common result: sensitivity of subthreshold production to coupling to baryonic resonances important interference effects expected between I=0 (ω) and I=1 (ρ) channels hadronic coupled channel models fitted to γp  ρ/ω p and  - p  ρ/ω n data Coupling constants N(1535) N(1680) -pρn-pρn -pωn-pωn N(1535) N(1440) N(1675) N ρ/ωρ/ω R e+e+ e-e- N(1440) M ee =0.6 GeV/c 2

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

25. Electromagnetic form factors approach Trento, 20/05/2013 B. Ramstein 25 M. Zetenyi and G. Wolf, Phys.Rev. C86 (2012) 065209 ρ production is embedded in the em form factor R R s channel u channel adjustment to pion photoproduction cross sections of RN  couplings (within the range allowed by the radiative decay widths) γp  + n + Born term + ρ meson exchange π - p  ne + e - Further studies needed: Inclusion of ω contribution Too large cross sections for ρ production Further studies needed: Inclusion of ω contribution Too large cross sections for ρ production

26. Simulations using the resonance model B. Ramstein 26 « photon-point » M. Zetenyi, Gy. Wolf, nucl- th0202047  e+e+ e-e- R N Form factors: M ee (GeV/c 2 ) Missing mass selection p=0.8 GeV/c  s=1.55 GeV/c after missing mass cut  - p  e + e - n Dalitz decays H.Kuc (Orsay/Cracow) Missing mass (GeV/c) M ee (GeV/c 2 )

27. 27 π - p  ne + e - : count rate estimates Resonance model Coherent sum (M. Soyeur) incoherent sum (M. Soyeur) M.F.M. Lutz, B. Friman, M. Soyeur Nuclear Physics A 713 (2003) 97–118 H.Kuc Resonance model Titov et al.M. Lutz et al. Evts/week M>0.14 GeV/c 2 970~3000 ~100 P=0.8 GeV/c (below  threshold) 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 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  e+e+ e-e- R N

28. π N  ππ N: 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) 28 Trento, 20/05/2013 B. Ramstein Complete existing very precise photoproduction data Improve knowledge of baryonic resonances, M R,  (N*  N π ),  (N*  N ππ ) 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)

29. 29 Trento, 20/05/2013 Important coupled channel effects With BR( ρN)~20%, cross sections are not reproduced need for differential cross sections Important for medium effects Manley et al. strong N(1520)  2  BR(ρN)~20% N(1520) D 13 state Branching ratios to π Δ and (π π) s N need to be checked   N -1 N(1520) Existence contradictory Not seen in the latest PWA analysis BR(2π) =40 to 90 % (PDG 2010) Some open issues for πN  ππN and πN  πN measurements N(1440) P 11 N(1710) P 11 Coupled channel Giessen / Manley

30. Trento, 20/05/2013 B. Ramstein 30 acceptance  p/p =8% Momentum measurement needed Trigger on interactions with the target, halo rejection in beam, position sensitive detectors optimization of pion production yield (duty cycle, primary beam intensity) optimization of beam line acceptance and extension at the target X,Y det1 X,Y det2

31. Pion Beam tracking Trento, 20/05/2013 B. Ramstein 31 10x10 cm 2 2x128 channels 300  Si detector L. Fabbietti’s group. Excellence Cluster Universe, Garching Beam line optimization: Orsay  p/p~0,1-0.3 %  x<1mm Diamond start detector GSI

32. Béatrice Ramstein 32 Conclusion: Conclusion: perspectives of pion beam experiments with HADES ( 2014) Strangeness production in  - A at 1.7 GeV/c  - p  ne + e - at 0.8 GeV/c GSI pion beam is unique in world at present to provide these data This should be exploited,…. before HADES moves to FAIR GSI pion beam is unique in world at present to provide these data This should be exploited,…. before HADES moves to FAIR Trento, 20/05/2013 Unique chance to study Time-Like electromagnetic structure of higher lying resonances/coupling to ρ/ω mesons (complementary to pion electroproduction) Urgent need of new data for Partial Wave Analysis  baryonic resonance properties Energy scan of  - p reactions : one pion, two pion and kaon production Elementary reactions are very important to control the interpretation of medium effects (lesson from HADES dilepton experimental program )

33. Thank you Trento, 20/05/2013 33 B. Ramstein

34. 34 Simulations for dilepton production below  threshold after missing mass cut  - p  e + e - n M ee (GeV/c 2 ) P=0.8 GeV/c Important interference effects expected between I=0 (ω) and I=1 (ρ) channels Linked to coupling to baryonic resonances Calculations based on hadronic couplings M. Lutz, B. Friman, M. Soyeur, NPA 713 (2003) 9 Titov and Kämpfer EPJA 12 (2001) 217 H. Kuc PhD Orsay/Cracovie Efects of electromagnetic form factors ? Simple resonance model: Dalitz decay of different baryonic resonances with constant form factors + meson contribution Very new calculation based on VDM transition form factors by Zetenyi and Wolf arXiv:1208.5671v1 [nucl-th] arXiv:1208.5671v1 Trento, 20/05/2013 34 B. Ramstein

35. Trento, 20/05/2013 B. Ramstein 35

36. Trento, 20/05/201336 two component model: fit of parameters to existing data elastic nucleon form factors 4 parameters a 2, , g 8,v GMp/pFdGMp/pFd G E p /F d G M n /  n F d GEnGEn N-  magnetic transition form factors 2 additionnal parameters: a’,g 10 G M N-  /3G D best fit a’/a= 1.27 g 10 /g 8 =1.28 B. Ramstein GMpGMp Time-Like

37. Towards a consistent description of dilepton production in all systems 37 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 Confirmation of DLS data ! predictions HSD: E. Bratkovskaya et al. arXiv:1301.0786arXiv:1301.0786 [ Trento, 20/05/2013 B. Ramstein

38. 38 Lecture III: 38 Technical layout of HADES Pre-Shower TOF outer MDC RPC He pipe Start + target Cryostat beam outer MDC inner MDC B field region inner MDC RICH readout HADES cave HADES sector Trento, 20/05/201338 B. Ramstein

39. Trento, 20/05/2013 B. Ramstein 39 G. Agakishiev et al., Phys.Lett. B715 (2012) 304-309 ω not modifed, but absorbed clear excess in p+A below vector meson pole  - secondary reactions  +N  (1720,..)(N * (1520),..)  N ρ  Ne + e - - Electromagnetic Time-Like form factors ? Studying cold nuclear matter in p+Nb at 3.5 GeV First measurement of lepton pairs with p e+e- < 0.8 GeV/c radiated from cold matter ( not measured by CLAS, KEK-E325)

40. Beatrice Ramstein Sesimbra, May 2009 40 accounting of the in-medium effects - a collisional broadening and dropping mass of the vector mesons  – leads to changes of the final spectra: accounting of the in-medium effects - a collisional broadening and dropping mass of the vector mesons  – leads to changes of the final spectra: - reduction of the  peaks - enhancement of the dilepton yield for 0.4<M<0.7 GeV effect is stronger for heavy nuclei effect is stronger for heavy nuclei HSD’09  similar to W. Cassing, Y.S. Golubeva, A.S. Iljinov, L.A. Kondratyuk, Phys. Lett. B 396 (1997) 26 HSD: p r eliminary  E. Bratkovskaya (Frankfurt) New HSD calculations emphasizes interest of subthreshold production (via N(1520) resonance) emphasizes interest of subthreshold production (via N(1520) resonance) Medium effects are predictedMedium effects are predicted