1 / 31

Time-Like Baryon Transitions studies with HADES

N. R. e +.  . e -. Time-Like Baryon Transitions studies with HADES. Béatrice Ramstein, IPN Orsay, France f or the HADES collaboration. MESON 2018, Cracow , June 7 — 12, 2018. N. R. e +.  . e -. Outline. Introduction General motivations of the HADES experiment

kyokom
Download Presentation

Time-Like Baryon Transitions studies with HADES

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. N R e+  e- Time-Like Baryon Transitions studies with HADES Béatrice Ramstein, IPN Orsay, France for the HADES collaboration MESON 2018, Cracow , June 7 — 12, 2018 B. Ramstein

  2. N R e+  e- Outline • Introduction • General motivations of the HADES experiment • Access to time-likeelectromagnetic baryon transitions • Resultsfrom pp and pnreactionswith HADES at GSI • Preliminaryresultswith the GSI pion beam • Prospects for hyperon transitions • Conclusions B. Ramstein

  3. HADES: exploring dense QCD matter • Observables: • Correlations and fluctuations • Collective effects • Strangeness • Dileptons B. Ramstein

  4. in-medium  meson Strong broadening of the in-medium  due to the coupling to baryon resonances HADES data Preliminary Au+Au 1.25A GeV medium contribution N*N couplings • Rapp, Chanfray and Wambach NPA 617, (1997) 472 • Rapp and Wambach EPJA 6 (1999) 415 • Global understanding of dilepton production from RHIC to SIS18 energies • Still to bebetterconstrained by elementaryreactions Coarse-grained UrQMD: CG FRA Phys. Rev. C 92, 014911 (2015) CG GSI-Texas A&M Eur. Phys. J. A 52 5 (2016) 131 CG SMASH: arXiv: 1711.10297 [nucl-th] HSD: Phys. ReV. C 87, 064907 (2013) Robust understanding across QCD phase diagram B. Ramstein

  5. Role of baryonicresonancesin e+e-production at 1-3 AGeV • Mesonicdecays: N/ N, N, N • ° Dalitzdecay: ° e+e- (BR  1.2 %)  (1232)  N0, N (1520)  N0,… •  Dalitzdecay:  e+e- (BR  0.6 %) N(1535) N,…. •  Dalitzdecay0e+e- (BR 7.7 10-4 ) • /ωdirect decay/ω  e+e- (BR  4-7 10-5) • Dalitzdecay of baryonicresonances: /N* Ne+e- not measured ! Vector Dominance Time-likeelectromagneticformfactors B. Ramstein

  6. Dalitzdecay of baryons: • A way to accesselectromagnetic structure of baryon transitions at low q2 in the time likeregion • Most information comes from the spacelike (q2<0) region • Time like (q2> 0 ) region : analyticallyconnected to spacelike Dalitzdecay 0< q2 <(MB’-MB)2 q2= M ee2 Annihilation q2 > (MB+MB’)2 Scatteringq2<0 q2=0 B’B B. Ramstein

  7. HADES High AcceptanceDiElectron Spectrometer at GSI, Darmstadt Acceptance:Full azimuth, polar angles 18o - 85o Particle identification:e+/e-, +/- , K+/K-, p RICH,Time Of Flight, Pre-Shower (pad chambers & lead converter) ( also MDC (K)) Trigger: ~ 50 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 • New ElectromagneticCalorimeterjustinstalled • ForwardDetector (0.5-7°) • to beready end of 2018 7 B. Ramstein

  8. The Collaboration SIS • Cracow(Univ.), Poland • Darmstadt (GSI), Germany • Dresden (FZD), Germany • Dubna (JINR), Russia • Frankfurt (Univ.), Germany • Giessen (Univ.), Germany • Jülich (FZJ), Germany • München (TUM), Germany • Moscow (ITEP,MEPhI,RAS), Russia • Nicosia (Univ.), Cyprus • Orsay (IPN), France • Rez (CAS, NPI), Czech Rep. • Sant. de Compostela (Univ.), Spain • Wuppertal (BUG), Germany • Coimbra (Univ.), LIP, Portugal GSI 8 B. Ramstein

  9. Hadesexperimental program • dense and hot matterstudies • C+C 1 and 2 GeV/nucleon, Ar+KCl 1.75 GeV/nucleon, Au+Au 1.25 GeV/nucleon • cold matter at normal nucleardensity p+Nb 3.5 GeV, -+W/C 1.7 GeV/c • Dileptonemission in elementary collisions pp, dp and -p • Reference to heavy-ion spectra • Dalitzdecays of baryon resonances • Simultaneousmeasurements of hadronicchannels(inclusive and exclusive meson • production 1, 2, , ,  ,…) • Production mechanism • Baryon spectroscopy (baryonicresonancecouplings,..) • Partial WaveAnalysis: pppp0, pppn+, -pn+ -, -pp 0- • …. strangenessmeasurement program: K- , K0, , (1385), (1405), p correlations • ( J. Wirth B4 Friday 18:20) B. Ramstein

  10. (1232) Dalitzdecay: branching ratio and formfactors ppppe+e- E=1.25 GeV • and 0 production cross section deduced from PWA • of one pion production channels • HADES, Eur. Phys. J. A 51 (2015) 137 π° Dalitz: π°e+e- pp BremsstrahlungShyam and Mosel, , PRC82 (2010)062201 Deviation from « point-like » transition Helicity distributions *  e+e- Consistent with transverse : Fit result : d/dcos ~ 1 + B cos2 B=1.170.34 HADES, Phys.Rev. C95 (2017) 065205 first measurement of (1232) Dalitzdecaybranching ratio BR( Ne+e-) = 4.19  0.42 (model)  0.46 (syst.)  0.34 (stat.) 10-5. B. Ramstein HADES coll., Phys.Rev. C95 (2017) 065205

  11. pnpne+e- : dilepton production from charged currents Much larger production at large Mee than in pp S&M: Shyam &Mosel Phys. Rev. C 82:062201, 2010 B&C Bashkanov & Clement Eur. Phys. J. A 50, 107 (2014) Helicity angles „-like” systematic studies (WASA and HADES) pp pp+-, nn++, pp00 pn d+- , d00, pn+- , pp°-  170 b fixed from 2 pion data „-like” Reasonabledescription by bothmodels cos(e ) cos(e) B. Ramstein

  12. Dilepton production from higher lying resonances Effect of electromagnetic transition FF for light baryonic resonances (N(1520),…) ppe+e- p+ppp e+e - 3.5 GeV ω R  ρ Inclusive e+e- production reproduced by resonance model withρNN* couplings Dalitzdecays of point-like baryonic resonances constrained by ppπ0 and pnπ+ channels ppe+e- + “direct” ρ and ω ω R  G. Agakishiev et al. Eur.Phys.J. A50 (2014) 8 J. Weil, et al., EPJA 48, 111 (2012) B. Ramstein

  13. 2 production channels pppp+- E=3.5 GeV Extraction of one and two baryon production cross sections preliminary  production angular distribution A. Belounnas et al., HADES coll. , Pos(HADRON2017)213 Important constraints for dilepton production More details in Amel Belounnas’stalk (B5 Monday16:05 ) B. Ramstein

  14. Pion beam at GSI Pion beamtracker Diamond detectors HADES GSI pion beam momentum0.6 < p <1.7 GeV/c pion flux ~ 106/s at 1 GeV/c 2 Double-Sidedsiliconsensors 100 x100mm2, 300μm thick 2 x128 channels ω η Pion momentumacceptance=2% ResolutionΔp/p < 0.3% B. Ramstein

  15. N R e+  e- Pion beamexperimentwith HADES • 2014 commissioningexperiment • Use of Polyethylene (CH2)n and Carbontargets • Motivations: investigate the N(1520) region • +  - and -° production in an energy scan (4 measurements s=1.46-1.55 GeV/c2) • Improve database for baryon spectroscopy: 2N =N,N,  branchings • e+e- production s=1.49 GeV/c2 • Resonance Dalitz decays R→Ne+e- • (Link to time-like transition electromagnetic structure) • No existing data Subtraction of C contribution and Normalisation using π-+p elasticscattering SAID data (deg) MM2(GeV2/c2) B. Ramstein

  16. Bonn-Gatchina Partial WaveAnalysis in 2 production channels HADES data corrected for acceptance • collaboration with A. Sarantsev (seenext talk) • HADES data (π-p nπ+π- and π-ppπ0π- at 4 energies ) • + photon (CB-ELSA,MAMI) and pion (Crystal Ball) data base Extraction of N, N, N components in the different partial waves e.g. N(1520): N coupling =122 % PDG 2015 : 15-25% PDG 2016 : no info More details in IzabelaCiepal’s talk (B6 Monday 16:55 ) • New HADES data are crucial for the determination of the  contribution • Still no data on  between 1.54 and 1.75 GeV/c2 (part of HADES future program) B. Ramstein

  17. Inputs for -pXe+e- from PWA preliminary HADES n - total 3/2- (D13+..) 1/2- (S11+..) 3/2+ (P33+.. -p+- n s(MeV) -pn 0 Mesonexchange (b) -p-0p n-p 0 production from PWA -pn 0 -pn 0 0 -pp -0 s(MeV) Cross section for -p n (detailed balance) input for -p e+e-n off-shell  productionin -p  1.3 mb at 0.69 GeV/c t-channelcontribution issmall B. Ramstein

  18. Inclusive e+e- production 0 -+CH2e+e-X p=0.69 GeV/c • PLUTO eventgeneratorFröhlich et al, POS (2007) 076 • π-p: • 0e+e- (SAID)  e+e- (Landolt-Börnstein) •  contribution from PWA (-pn 1.3 mb) • effective point-like contribution deduced from • n-p withe+e- distribution as N(1520)0 ne+e- • π-C: • quasi-free process(momentumdistr. of • nucleonstakenintoaccount) scaledto C /H 4 • Simulations filtered by acceptance 0 « N(1520) »   preliminary Measurement on CH2 target: (d/dM)H+0.5 (d/dM)C C  4 H Signal (M<140 MeV/c2) = 13138 Signal (M>140 MeV/c2) = 3300 • Strongη contribution • Cocktail of point-like sources underestimates the e+e-yieldat high invariant mass • Satisfactory description adding off-shell contribution B. Ramstein

  19. Exclusive e+e- production with pion beams e+  e- 0.9 <Mmissee< 1.03 GeV/c2 Total π0 e+e-γ ηe+e-γ N(1520)ne+e- π-pne+e- preliminary preliminary π-pne+e- π-pn+- Minvee > 0.12 GeV/c2 1500 events preliminary PWA Off-shell ρe+e-  Off-shell ρπ+π- I=1 Minvππ(GeV/c2) Vector Dominance Model (d/dMee)= (d/dM )* BR(Mee=M) * (M/Mee)3 • Empiricalway of takingintoaccount VDM formfactors for baryon electromagneticdecays B. Ramstein

  20. N(1520) and N(1535) contributions • PLUTO eventgeneratorFröhlich et al, POS (2007) 076 • π-p: • Meson production: Landolt-Börnstein • 0e+e-  e+e- •  contribution from PWA • N(1520) and N(1535) contributions from PWA • in -p reactions + real  couplings • Non-resonant contributions missing preliminary 0 -+CH2e+e-X p=0.69 GeV/c 0  On-goingwork to takeintoaccount time-likeelectromagneticform factor for N(1520) N transition N(1520)  N(1535) G. Ramalho and T. Pena Phys. ReV. D 95014003 B. Ramstein

  21. N R e+  e- Information on time-likeelectromagnetic structure from angular distributions Spin density matrix formalism: E.Speranza et al. Phys.Lett. B764 (2017) 282-288 A. Sarantsev (ECT* meeting, May2017)  |A|2= • 3 independentdensity matrix elements:11 , 10,1-1 depending on Mee and  • contain information on electromagnetic structure • e.g. pure transverse (E/M): 11 =1/2, 10 =0 • Related to helicity amplitudes and/or formfactors B. Ramstein

  22. Very first results on density matrix elements Quasi-free -pne+e- s=1.49 GeV/c2 Microscopic model s and u channels: N(1440) and N(1520) with VDM formfactors: B. Friman, M. Zetenyi, E. SperanzaPhys.Lett. B764 (2017) 282-288 Mee> 400 MeV/c2 • Despitelowstatistics, significant information on the electromagnetic structure of the transition • Presence of longitudinal contribution • 11consistent with pure N(1520) in VDM model preliminary Transverse Cos *CM Federico Scozzi et al. (HADES coll.) EPJ Web Conf., 137 (2017) 05023 Exp. proposal at GSI/SIS18 (2018-2019) : explore the thirdresonanceregion (s~1.7 GeV/c2) channels: -p ne+e- , -p N, n, n , K0, K,….+photons (new electromagneticcalorimeter) Possiblyafter 2019: s~2 GeV/c2region((1405),…) B. Ramstein

  23. HADES upgrade New ECAL (lead glass) E/E ~5%  and e+/e-detection New RICH photon detector & read-out (coll. with CBM@FAIR) Gain in e+e-efficiency x5 Forward detector (0.5-6.5°) Straws + RPC TOF (coll. with PANDA@FAIR) (x)~150 m (TOF)~70 ps B. Ramstein

  24. Future plans : hyperonDalitzdecays • Hyperons are narrow (=15-40 MeV) : can be studied in pp, pA with HADES • (and later pp with PANDA at FAIR). • Radiative decays of hyperons Y  • Badlyknown • High sensitivity to internal structure (quark correlations ) • Dalitz decays of hyperons Y  e+e- (BR~10-5) • No measurement. • Relevance of Vector Dominance in the hyperon sector? - R. Williams et. al. PRC48(1993)1381 K-p Y * e.g. *(1385)* is anologue of (1232)N* transition (measured by HADES) calculations C. Granados et al. Eur. Phys. J.A54(2018)1. p+pK++(1520)+p |  (1115)+ (0.85%) (1115)+e+e- (8 10-5) Feasibilitystudy: about 25events/day in pp at 4.5 GeV  (1520) e+e- (poster: K. Nowakowski) (Me+e-) 2 B. Ramstein

  25. Conclusion and outlook • Pioneeringstudies for Time-Likeelectromagnetic baryon transitions •  Dalitzdecaybranching ratio and VDM effects (pp reactions), • N(1520) region ( pion beam) • 2 channels: baryon spectroscopy • For mid-term future, in parallel to the program on medium effects • InvestigateheavierresonancesΔ(1620), N(1720),… • in e+e-channels and manyhadronicchannels, • e.g. -pn , K0, K,…. • Electromagneticdecays of hyperons in pp reactions : Y, Ye+e- • Higheracceptance(Forward Detector)+ ElectromagneticCalorimeter Pave the way for future mesonbeamfacilities seeW. J. Briscoe ‘s talk • After 2025: HADES experiments at FAIR • (p and ion beams, possibly pions in future….) B. Ramstein

  26. Thankyou B. Ramstein

  27. Time-likeform factor models • e-VDM model (,’,’’,…) M. Krivoruchenko, Ann. Phys. 296 (2002) 299 • Currentlybeingupdated(work in progress) to recent data • - SL transition FF (CLAS) • - ρ/ωNN* couplings (PWA) • Two-component model (real photon +vectormesoncouplings) • Zetenyiand Wolf, Phys. Rev. C 86 (2012) 065209 N-(1232) • constituent quark model • existing for N-Δ(1232) • Wan and Iachello, Int. J. Mod. Physics A20 (2005) 1846, • I. Fröhlich et al., Eur.Phys.J. A45 (2010) 401-411 SpaceLike core • constituent quark-core+ meson cloud • existing for N-Δ(1232) and N-N(1520) • G. Ramalho, T. PenaPhys.Rev. D85 (2012), 113014 • G. Ramalhoet al., Phys. Rev. D93, 033004 (2016) • G. Ramalho, T. PenaPhys. Rev. D95 (2017), 014003 Time Like core B. Ramstein

  28. B. Ramstein

  29. e-  * e+  N (1232) Dalitzdecay: angular distributions and branching ratio • ppppe+e- E=1.25 GeV Non-resonantBremsstrahlungsubtracted Acceptancecorrected  Production Helicity distributions *  e+e- scaled  contribution from pppp0(PWA)  Dalitzdecay simulation (Ramalho&Penaform factor) Only transverse :d/dΩe~ 1+cos2 Fit result : d/dcos ~ 1 + B cos2B=1.170.34 HADES coll., Phys.Rev. C95 (2017) 065205 B. Ramstein

  30. More about strangeness: understand the (1321) production • Doubly strange baryons () (S= - 2) • -(1321) • unexpected high yieldmeasured by HADES • belowthresholdArKCl(-640 MeV) et pNb (-70 MeV) •  Elementarymechanism to beunderstood | + - (63%) | -+p HADES collab PRL103(2009)132310 HADES collabPRL114(2015) 212301 Simulations: p+p 4.5 GeV=4.5b 500 -(1321) reconstructed/ hour B. Ramstein

  31. Dileptons as a probe of dense matter Excessdileptonyieldused to characterize the dense hadronic phase • Spectrometer • Thermometer • Chronometer • Barometer • Polarimeter Thermal origin • g* polarizationvia lepton angulardistribution • Teffvs. Mll • v2 vs. Mll • Mllof excess pairs preliminary Fireball duration Polarization Density dependence Recentresults from Au+Auexperiment: SeeT. Galatyuk, Quark Matter 2018 B. Ramstein

More Related