Perspectives of recent HADES experiments with a pion

Perspectives of recent HADES experiments with a pion beam B. Ramstein, IPN Orsay 16/12/2014, GDR annual meeting, Ecole Polytechnique GDR 2014 B. Ramstein 1

Outline q. Introduction: General motivations of HADES experiments q Results from NN reactions with HADES Role of baryonic resonances in dilepton emission q Perspectives of HADES measurements with the GSI pion beam ( data taking in summer 2014) q. Conclusions GDR 2014 B. Ramstein 2

Dileptons: a probe of in-medium vector meson modifications: Present explanation of dilepton spectra at ultra-relativistic energies (NA 60, STAR, PHENICS) « in-medium broadening » In-medium spectral function depends on NN* coupling main players: N(1520), N(1720), (1910) Rapp and Wambach EPJA 6 (1999) 415 Rapp, Chanfray and Wambach NPA 617, (1997) 472 Dominant source of mesons at ultra relativistic energies + - Source of mesons at 1 -2 AGe. V NN NR NN N R N Coupling of ρ to baryonic resonances can be studied in NN and N collisions at 1 -2 Ge. V GDR 2014 B. Ramstein 3

The Collaboration Catania (INFN - LNS), Italy Cracow (Univ. ), Poland Darmstadt (GSI), Germany Dresden (FZD), Germany HADES strategy: Dubna (JINR), Russia Frankfurt (Univ. ), Germany e+e- , strangeness, charged hadron production Giessen (Univ. ), Germany Milano (INFN, Univ. ), Italy Nuclear matter studies: A+A, p+A, π-+A München (TUM), Germany Moscow (ITEP, MEPh. I, RAS), Russia Nicosia (Univ. ), Cyprus Elementary reactions p+p, quasi-free np, π-+p Orsay (IPN), France Rez (CAS, NPI), Czech Rep. SIS Sant. de Compostela (Univ. ), Spain Valencia (Univ. ), Spain GDR 2014 Coimbra (Univ. ), LIP, Portugal B. Ramstein 4

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 )) HADES 2 nd generation dilepton spectrometer SIS Trigger: ~ 50 k. Hz 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 Electromagnetic Calorimeter for experiments with SIS 100/FAIR GDR 2014 Larger plane of drfit chambers built at IPNO B. Ramstein 5

Exclusive analysis : pp ppe+e- at 1. 25 Ge. V p p 1 p + p 2 q 2=M 2 inv(e+e-)=M 2 * e+ e- • Supported by the analysis of 1 production channels Ph. D T. Liu Orsay 2010 HADES collab: E. P. J. A 48 (2012) 74 • on-going Partial Wave Analysis (collab. With Bonn-Gatchina) First measurement ! Dalitz decay branching ratio in agreement with QED value (4. 2 10 -5) BR= 4. 42 10 -5 20% ( syst. ) 9% (stat) 6

pp e+e-X E=2. 2 Ge. V, 3. 5 Ge. V Comparison to cocktail of point-like dilepton sources • Direct production of / • Dalitz decay of resonance (point-like) E=2. 2 Ge. V Exclusive analysis G. Agakishiev et al. Eur. Phys. J. A 50 (2014) 8 E=3. 5 Ge. V Hades data, EPJA 48 (2012) 64 Hades data, PRC 85 054005 (2012) Effect of electromagnetic form factors / Coupling of to baryonic resonances ? GDR 2014 B. Ramstein 7

From NN to πN reactions J. Weil, H. van Hees and U. Mosel, EPJA 48, 111 (2012) Gi. BUU transport model q ρ is modified in elementary collisions, due to coupling to baryonic resonances q Strong constraints for medium effects interpretation pp 3. 5 Ge. V R N e+ e- N*/ N-1 Advantages of -p ne+e- : q interaction better known q fixed mass of the resonance in s channel q much larger acceptance for exclusive channels ü electromagnetic -p ne+eü hadronic -p p --, n + --, p 0 -GDR 2014 B. Ramstein 8

Pion beam experiments SAID, data base, CNS, GWU http: //gwdac. phys. gwu. edu 114 kevents 72 kevents 1. 4 1. 6 1. 8 All what we know about N* couplings to ρN, π, N is based on the analysis of 240000 events (bubble chamber < 1980) 2. s (Ge. V) GSI pion beam momentum 0. 6 < p <1. 5 Ge. V/c Unique facility in world at present able to bring new pion beam data η ω B. Ramstein 9

Pion beam experiments Diamond detectors Pion beam tracker: 2 Double-Sided Silicon sensors 100 x 100 mm 2, 300μm thick 2 x 128 channels Beam optics calculation: responsibility IPNO q Two beam periods at GSI in summer 2014 in beam sharing mode q Restricted program due to limitations on • Beam time: last operation period before SIS 100 integration (FAIR) • Pion flux: up to 120000/s (radiation safety limit) GDR 2014 B. Ramstein 10

Pion beam: in-medium strangeness production 1 st data set: π-+A p=1. 7 Ge. V/c main goal= strangeness production K+ K- Λ ϕ 4. 2 k 92 k 213 target K 0 W 102 k 100 k C 129. 5 k 99. 7 k 6. 9 k _S ry a n i φ production im rem p ery V 78. 6 k 398 Interest of IRFU to include strangeness in INCL cascade calculations GDR 2014 B. Ramstein 11

Pion beam: ρNN(1520) couplings 2 nd data set: energy scan in π - + p around N(1520) Main goal: determine precisely the ρNN(1520) couplings by measuring -p -p, -p - +n, -p - 0 p crucial to constrain the predictions of in-medium modifications of the ρ meson spectral function fundamental interest: structure of N(1520) Controversial results with Manley PWA analysis: V. Shklyar Hades symposium, Seillac 2011 Bonn-Gatchina PWA analysis π-p π+π p dominated by Δπ contribution ρ contribution factor 10 lower GDR 2014 B. Ramstein 12

Quality of pion beam data : di-pion production π+π- production ry rem na imi yp r e V GDR 2014 B. Ramstein (CH)n C 13

Pion beam: dielectron channels 3 rd data set: π - + p n e+e- at s=1. 49 Ge. V close to N(1520) pole mass and below η threshold Main goal : Time-Like electromagnetic structure of N-N(1520) transition/ coupling to ρ meson Controversial yield predictions: Highly dependent on ρNN* couplings and ρ/ω interference • B. Kaempfer , A Titov , R. Reznik NPA 721(2003)583 M. F. M. Lutz , B. Friman, M. Soyeur Nuclear Physics A 713 (2003) 97– 118 • R N e+ e- VDM electromagnetic form factors: M. Zetenyi and G. Wolf, Phys. Rev. C 86 (2012) 065209 • • Resonance model: J. Weil Sensitivity of Mee distribution to to Δπ and ρN contributions (Bonn-Gatchina predictions) GDR 2014 B. Ramstein 14

Pion beam : quality of di-electron channels Dielectrons from (CH)n target Mee>0. 12 Ge. V/c 2 Contribution of C under the neutron peak ~25% , can be easily subtracted selection of about 300 evts π - + p ne+e. Mee>140 Me. V/c 2 m ry e V li e r p π - + p Xe+e- ry a in n On-going analysis : Electron ID, Combinatorial Background subtraction, …. F. Scozzi, Ph. D (IPNOrsay, TU Darmstadt) GDR 2014 B. Ramstein 15

Conclusion HADES results (focus on pp/pn reactions) q selective study of e+e- production from Dalitz decay of baryonic resonances sensitivity to Baryonic resonances Time-Like electromagnetic structure/coupling to ρN q Indispensable complement for in medium studies Recent pion beam experiment q Very promising data: strangeness, π+π-, e+eq expected precise determination of N(1520) coupling to ρN q Continuation at SIS 18 in 2017 -2018 ? HADES at FAIR : pp, p. A with an ECAL GDR 2014 B. Ramstein 16

Hubert Kuc (codirection IPNO/UJ Kracow) Ph. D defense Thursday 18 December, Salle des conseils IPN Orsay, 14 h 30 « Di-pion and di-electron production in quasi-free np reactions with HADES » Thank you GDR 2014 B. Ramstein 17

Baryon Resonance electromagnetic Dalitz decays π π + QED: point-like R- * vertex M. Zetenyi et al. PRC 67, 044002 (2003). - extended Vector Dominance Model M. I. Krivoruchenko et al. Ann. Phys. 296, 299 (2002). Fixed « Δ » mass p+p 3. 5 Ge. V GDR 2014 p+p 3. 5 Ge. V B. Ramstein Covariant model (bare quark core + meson cloud) G. Ramalho and T. Pena, Phys. Rev. D 85 (2012) 113014 18

Motivations of -p ne+e- experiments with HADES “off-shell ρ production” R N N(1520) e+ N-1 e- +. . . Time-Like electromagnetic form factors Space-Like electromagnetic form factors n e+ q 2 <0 fixed R Inverse pion electroproduction * e+ p * p q 2 > 0 variable R ee-- p studied at JLab/CLAS -p ne+e- below ρ/ω production threshold at s=1. 52 Ge. V/c 2 unique chance ü to study the Time-Like electromagnetic structure of N*(1520) ü to constrain the in-medium modifications of the ρ meson spectral function GDR 2014 B. Ramstein 19 19

The meson in hot and dense hadronic matter from SIS 18 to SPS Dilepton. Subtraction excess over oflong-livedsources G. Agakishiev et al. Phys. Rev. C 84 (2011) 014902 Arnaldi et al. , PRL 100, 022302 (2008) In +In 158 Ge. V/u mass shift excluded ! agreement with in-medium ρ meson broadening Source of mesons at 1 -2 AGe. V NN NR NN N R N Depends on RN coupling 20 B. Ramstein Source of mesons Dominant source of mesons at ultra relativistic energies + - GDR 2014 Coupling of ρ to baryonic resonances can be studied in NN collisions at 1 -2 Ge. V

21 B. Ramstein GDR 2014

πN Nπ π : Existing data 30 SAID, data base, CNS, GWU http: //gwdac. phys. gwu. edu 114 kevents 15 nπ+ πpπ- π0 72 kevents 30 15 69 kevents pπ+π0 nπ+π+ 7. 3 kevents 1. 4 1. 6 1. 8 W (Ge. V) 22 2. • More recent data (TRIUMF, LAMPF, BNL) do not cover the region between 1. 32 and 1. 9 Ge. V high statistics differential distributions are needed

Resonance excitation in 2 channel 2014: B-G (A. Sarantsev) K-matrix approach constraints from N, N N(1440, 1710) + (1910) N(1535) + (1620) N(1720) + (1600) N(1520) + (1700) N(1680) + (1905) N(1675) + (1925) - p R N, (I=0)N, (I=1)N + non resonant contributions Predictions: • s =1. 5 dominance of resonance channels D 13(1520) & P 11(1440) s