Electromagnetic and strong Electromagnetic and strong probes of compressed probes of compressed baryonic matter at SIS100 baryonic matter at SIS100 energies energies E E lena lena Bratkovskaya Bratkovskaya Institut für Theoretische Physik Institut für Theoretische Physik , Uni. , Uni. Frankfurt Frankfurt 27 April 2009, Meeting on ‘Nuclear Matter Physics at 27 April 2009, Meeting on ‘Nuclear Matter Physics at SIS 100‘ SIS 100‘ GSI, Darmstadt GSI, Darmstadt
Transcript
Electromagnetic and strong Electromagnetic and strong probes of compressed baryonic probes of compressed baryonic
matter at SIS100 energiesmatter at SIS100 energies
EElenalena Bratkovskaya Bratkovskaya
Institut für Theoretische PhysikInstitut für Theoretische Physik, Uni. Frankfurt, Uni. Frankfurt
27 April 2009, Meeting on ‘Nuclear Matter Physics at SIS 100‘27 April 2009, Meeting on ‘Nuclear Matter Physics at SIS 100‘GSI, DarmstadtGSI, Darmstadt
Our ultimate goals:Our ultimate goals:
• Study of the Study of the phase phase transitiontransition from from
hadronic to partonic hadronic to partonic matter – matter –
Quark-Gluon-PlasmaQuark-Gluon-Plasma
• Search for the Search for the critical pointcritical point
• Study of the Study of the in-mediumin-medium properties of hadrons properties of hadrons at high baryon density and temperature at high baryon density and temperature
The phase diagram of QCDThe phase diagram of QCD
SIS 100SIS 100
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-Im D (M,q,B,T) (GeV-2)
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Aim I. Study of in-medium effects within Aim I. Study of in-medium effects within transport approachestransport approaches
Accounting for in-medium effects requires Accounting for in-medium effects requires off-shell transport models off-shell transport models
Models predict predict changes of the particle properties in the hot changes of the particle properties in the hot and dense mediumand dense medium, e.g. broadening of the spectral function , e.g. broadening of the spectral function
HSDHSD** off-shell transport approach: off-shell transport approach:
Generalized transport equationsGeneralized transport equations on the basis of the Kadanoff-Baym on the basis of the Kadanoff-Baym equations for Greens functionsequations for Greens functions accounting for the first order gradient accounting for the first order gradient expansion of the Wigner transformed Kadanoff-Baym equations beyond expansion of the Wigner transformed Kadanoff-Baym equations beyond the quasiparticle approximation (i.e. beyond standard on-shell models)the quasiparticle approximation (i.e. beyond standard on-shell models)
The off-shell spectral functions change their properties dynamically The off-shell spectral functions change their properties dynamically by propagation through the medium and become on-shell in the vacuumby propagation through the medium and become on-shell in the vacuum
W. Cassing et al., NPA 665 (2000) 377; W. Cassing et al., NPA 665 (2000) 377; 672 (2000) 417; 677 (2000) 445672 (2000) 417; 677 (2000) 445
E. Bratkovskaya, NPA 686 (2001), E. Bratkovskaya, NPA 686 (2001), E. Bratkovskaya & W. Cassing, NPA 807 (2008) 214E. Bratkovskaya & W. Cassing, NPA 807 (2008) 214
Dileptons are an Dileptons are an ideal probeideal probe for vector meson spectroscopy in the for vector meson spectroscopy in the nuclear nuclear mediummedium and for the nuclear dynamics ! and for the nuclear dynamics !
• In-medium effects can be observed at In-medium effects can be observed at all energiesall energies from SIS to RHIC from SIS to RHIC
• The The shapeshape of the theoretical dilepton yield depends on the of the theoretical dilepton yield depends on the actual modelactual model for the in-medium spectral function for the in-medium spectral function => => Energy / system scan will allow to distinguish in-medium scenariosEnergy / system scan will allow to distinguish in-medium scenarios
FAIR energiesFAIR energies
J. Randrup et al., CBM Physics Book; J. Randrup et al., CBM Physics Book; PPRRC75C75 (2007) (2007) 034902034902
Modelling of in-medium spectral functions for Modelling of in-medium spectral functions for vector mesonsvector mesons
In-medium scenarios:In-medium scenarios:
dropping mass collisional broadening dropping mass + coll. broad.dropping mass collisional broadening dropping mass + coll. broad.
• Note:Note: for a consistent off-shell transport one needs not only in-medium spectral functions for a consistent off-shell transport one needs not only in-medium spectral functions but also but also in-medium transition ratesin-medium transition rates for all channels with vector mesons, i.e. the full for all channels with vector mesons, i.e. the full knowledge of knowledge of in-medium off-shell cross sections in-medium off-shell cross sections (s,(s,))
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HSD: Dalitz Dalitz Dalitz Dalitz Brems. NN Brems. N All
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HSD: Dileptons from C+C at 1 and 2 A GeV - HADESHSD: Dileptons from C+C at 1 and 2 A GeV - HADES
• HADES data show exponentially decreasing mass spectra HADES data show exponentially decreasing mass spectra • Data are Data are better described by in-medium scenarios with collisional broadening better described by in-medium scenarios with collisional broadening • In-medium effects are more pronounced for In-medium effects are more pronounced for heavy systemsheavy systems such as Au+Au such as Au+Au
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• NA60 data are better described byNA60 data are better described by in-medium scenario with collisional broadening in-medium scenario with collisional broadening
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HSD: free s. f. coll. broad. dropp. mass
+ coll. broad.
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E. Bratkovskaya, W. Cassing, O. Linnyk, PLB 670 (2009) 428E. Bratkovskaya, W. Cassing, O. Linnyk, PLB 670 (2009) 428
High M tail not High M tail not reproduced in HSDreproduced in HSD
|||| Non-hadronicNon-hadronic
origin? origin?
Dileptons at SPS: CERESDileptons at SPS: CERES
CERESCERES data aredata are better describedbetter described by an in-medium scenario withby an in-medium scenario with
E. Bratkovskaya, W. Cassing, O. Linnyk, PLB 670 (2009) 428E. Bratkovskaya, W. Cassing, O. Linnyk, PLB 670 (2009) 428
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: free s.f. : coll. broad. total yield (coll. broad.)
HSD 'cocktail' : dropp. mass + coll. broad.
x 10-6
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<dN
e+ e-(tot
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Olena Linnyk
right hand side picture (Pb+Au) has arial font in it that my comp does not have
Dileptons at SIS-100Dileptons at SIS-100
For in-medium scenarios For in-medium scenarios with with collisional broadening + dropping collisional broadening + dropping mass:mass:strong broadening of strong broadening of -meson -meson spectraspectra reduction of the yield at the reduction of the yield at the ‚free‘ pole mass ‚free‘ pole mass
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Au+Au, 10 A GeV, b=0.5 fmmedium effects: CB+DM HSD:
Dalitz Dalitz Dalitz Dalitz All
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HSD: free coll. broad. coll. broad. + drop. mass.
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Dileptons at SIS-100Dileptons at SIS-100
Dileptons at SIS-100 : Dileptons at SIS-100 : ‚free‘ vs. ‚in-medium‘ scenarios (‚free‘ vs. ‚in-medium‘ scenarios (collisional broadeningcollisional broadening , ,collisional broadening +dropping masscollisional broadening +dropping mass)) for vector mesons for vector mesons
enhancement enhancement of dilepton yield for 0.2<M<0.7 GeV and of dilepton yield for 0.2<M<0.7 GeV and reductionreduction at M~m at M~m
for all SIS-100 energies!for all SIS-100 energies!
Ratio = dN/dM(in-medium) / dN/dM(free)Ratio = dN/dM(in-medium) / dN/dM(free)
enhancement enhancement of dilepton yield for 0.2<M<0.7 GeV and of dilepton yield for 0.2<M<0.7 GeV and reduction reduction at M~mat M~m for all SIS-100 energies from 2 to 14 A GeV! for all SIS-100 energies from 2 to 14 A GeV!
Our ultimate goals:Our ultimate goals:
• Study of the Study of the phase phase transitiontransition from from
hadronic to partonic hadronic to partonic matter – matter –
Quark-Gluon-PlasmaQuark-Gluon-Plasma
• Search for the Search for the critical pointcritical point
• Study of the Study of the in-mediumin-medium properties of hadrons properties of hadrons at high baryon density and temperature at high baryon density and temperature
The phase diagram of QCDThe phase diagram of QCD
SIS 100SIS 100
From hadrons to partonsFrom hadrons to partons
In order to study of the In order to study of the phase transitionphase transition from from hadronic to partonic matter – hadronic to partonic matter – Quark-Gluon-PlasmaQuark-Gluon-Plasma – – we we need need a a consistent transport model withconsistent transport model withexplicit explicit parton-parton interactionsparton-parton interactions (i.e. between quarks and gluons) (i.e. between quarks and gluons) outside strings!outside strings!explicit explicit phase transitionphase transition from hadronic to partonic degrees of freedom from hadronic to partonic degrees of freedomlQCD EoS lQCD EoS for partonic phase => for partonic phase => phase transition is always a cross-overphase transition is always a cross-over
Transport theoryTransport theory: off-shell Kadanoff-Baym equations for the : off-shell Kadanoff-Baym equations for the Green-functions GGreen-functions G<<
hh(x,p) in phase-space representation; (x,p) in phase-space representation;
with thewith the partonic partonic andand hadronic phase hadronic phase
W. Cassing, E. Bratkovskaya, PRC 78 (2008) 034919W. Cassing, E. Bratkovskaya, PRC 78 (2008) 034919W. Cassing, W. Cassing, EEPJ ST PJ ST 168168 (2009) (2009) 33
PHSD: Rapidity distributions at top SPSPHSD: Rapidity distributions at top SPS
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bin NA49 PHSD 1 2 3 4 5 6
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proton stoppingproton stopping
looks not bad !looks not bad !
pion and kaon dN/dypion and kaon dN/dybecome more narrow !become more narrow !
PHSD: Transverse mass spectra at top SPSPHSD: Transverse mass spectra at top SPS
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Central Pb + Pb at top SPS energiesCentral Pb + Pb at top SPS energies
PHSD gives harder spectra and works better than HSD at top SPS energies PHSD gives harder spectra and works better than HSD at top SPS energies
However, at low SPS (and FAIR) energies the effect of the partonic phase is However, at low SPS (and FAIR) energies the effect of the partonic phase is NOT seen in rapidity distributions and mNOT seen in rapidity distributions and mTT spectra spectra
PHSD: Strange and antistrange baryons at 160 A GeVPHSD: Strange and antistrange baryons at 160 A GeV
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Slightly more Slightly more Λ and Ξ Λ and Ξ but much more Ώ‘s !! but much more Ώ‘s !!
Antibaryons (r.h.s,) are Antibaryons (r.h.s,) are substantially enhanced !substantially enhanced !
Note: present statisticspresent statisticsdrastically need drastically need improvement !improvement !
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Strange and anti-strange baryons at SIS-100Strange and anti-strange baryons at SIS-100
PHSD vs. HSD:PHSD vs. HSD:enhancement of strange antibaryons is seen at 10 A GeV enhancement of strange antibaryons is seen at 10 A GeV (within present statistics !!!!)(within present statistics !!!!)
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partonic energy fraction vs centrality and energypartonic energy fraction vs centrality and energy
Dramatic decrease of partonic phase Dramatic decrease of partonic phase with decreasing energy with decreasing energy and centrality and centrality very small effect on pion and kaon observables at FAIR very small effect on pion and kaon observables at FAIR energies!energies!
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What is the matter at SIS-100 ?!What is the matter at SIS-100 ?!
The phase trajectories ((t),(t)) for central Au+Au collisions:
huge energy and baryon densities are reached ( >crit=1 GeV/fm3) at FAIR energies (> 5 A GeV), however, the phase transition might be NOT a cross-over at FAIR!
J. Randrup et al., CBM Physics Book; J. Randrup et al., CBM Physics Book; PPRRC75C75 (2007) (2007) 034902034902
1st order phase transition with critical point?
co-existance of partonic and hadronic degrees of freedom (in a mixed phase)
reducedfree energy
reduced volume
Maxwell construction
The Gibbs mixed phase(spatially separated domains)
Mixed phase concept
Generalized mixed phase (homogeneous)
(Slide from V. Toneev)
PHSD: Expanding fireball PHSD: Expanding fireball
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Time-evolution of parton densityTime-evolution of parton density
Time-evolution of hadron densityTime-evolution of hadron density
PHSD: PHSD: spacial phase ‚co-existence‘spacial phase ‚co-existence‘ of partons and hadrons, but of partons and hadrons, but NO interactions between hadrons and partons (cross-over)NO interactions between hadrons and partons (cross-over)
Summary Summary
• SIS-100 is well situated to study in-medium effectsSIS-100 is well situated to study in-medium effects due to due to the high baryon densities and long reaction timesthe high baryon densities and long reaction times
• dilepton spectradilepton spectra - according to the HSD predictions - show - according to the HSD predictions - show sizeable changes due to the different in-medium scenarios (as sizeable changes due to the different in-medium scenarios (as collisional broadening and dropping mass) which can be collisional broadening and dropping mass) which can be observed experimentallyobserved experimentally
• fraction of the partonic phase is small at FAIR energiesfraction of the partonic phase is small at FAIR energies => PHSD gives practically the same results as HSD => PHSD gives practically the same results as HSD (except (except for multi-strange antibaryons)for multi-strange antibaryons) when the lQCD EoS (where when the lQCD EoS (where the phase transition is always a cross-over) is used the phase transition is always a cross-over) is used
• isis the matter at SIS-100 a ‚mixed phase‘ ?the matter at SIS-100 a ‚mixed phase‘ ?
Open problemsOpen problems
• How to describe a How to describe a first-order phase first-order phase transitiontransition in transport ? in transport ?
• How to describe How to describe parton-hadron interactions parton-hadron interactions in a ‚mixed‘ phasein a ‚mixed‘ phase??
HSD & PHSD Team
HSD & PHSD Team Wolfgang CassingWolfgang CassingOlena LinnykOlena LinnykVolodya KonchakovskiVolodya Konchakovski
Viatcheslav D. ToneevViatcheslav D. Toneev and the numerous experimental and the numerous experimental friends and collegues !friends and collegues !
Thanks Thanks
-- END ---- END --
The Dynamical QuasiParticle Model (DQPM)The Dynamical QuasiParticle Model (DQPM)
Interacting quasiparticles :Interacting quasiparticles : massive quarks and gluonsmassive quarks and gluons
with spectral functions with spectral functions
T = 1.053 TT = 1.053 Tcc T = 1.35 TT = 1.35 TccT = 3 TT = 3 Tcc
•DQPMDQPM well matches well matches lQCDlQCD
•DQPMDQPM provides provides mean-fields for gluons and quarksmean-fields for gluons and quarks as well as as well as effective effective 2-body interactions 2-body interactionsand gives and gives transition ratestransition rates for the formation of hadrons for the formation of hadrons PHSDPHSD
Initial A+A collisions – HSD: Initial A+A collisions – HSD: string formation and decay to pre-hadronsstring formation and decay to pre-hadrons
Fragmentation of pre-hadrons into quarks:Fragmentation of pre-hadrons into quarks: using the quark spectral functions from the Dynamical QuasiParticle ModelDynamical QuasiParticle Model ( (DQPM) approximation to QCD
Partonic phase: Partonic phase: quarks and gluons (= quarks and gluons (= ‚dynamical quasiparticles‘)‚dynamical quasiparticles‘) with with off-shell spectral functionsoff-shell spectral functions (width, mass) defined by DQPM (width, mass) defined by DQPM
elastic and inelastic parton-parton interactions:elastic and inelastic parton-parton interactions: using the effective cross sections from the DQPM q + qbar (flavor neutral) <=> gluon (colored) gluon + gluon <=> gluon (possible due to large spectral width) q + qbar (color neutral) <=> hadron resonances
Hadronization: Hadronization: based on DQPM - based on DQPM - massive, off-shell quarks and gluons massive, off-shell quarks and gluons with with broad spectralbroad spectral functions hadronize tofunctions hadronize to off-shell mesons and baryons:off-shell mesons and baryons:gluons gluons q + qbar; q + qbar; q + qbar q + qbar meson (or string); meson (or string); q + q +q q + q +q baryon baryon (or string)(or string) (strings act as ‚doorway states‘ for hadrons) (strings act as ‚doorway states‘ for hadrons)
Consequences:Consequences: Hadronization:Hadronization: q+qbar or 3q or 3qbar fuse to q+qbar or 3q or 3qbar fuse to a a color neutral hadrons (or strings)color neutral hadrons (or strings) which furtheron decay to hadrons which furtheron decay to hadrons in ain a microcanonical fashion, i.e.microcanonical fashion, i.e. obeying all conservation laws obeying all conservation laws (i.e. 4-(i.e. 4-momentum conservation, flavor current conservation)momentum conservation, flavor current conservation) in each eventin each event Hadronization Hadronization yieldsyields an increase in total entropy San increase in total entropy S and not a and not a decrease as in the simple recombination model !decrease as in the simple recombination model !
Off-shell parton transportOff-shell parton transport roughly leads a roughly leads a hydrodynamic evolutionhydrodynamic evolutionof the partonic systemof the partonic system
E.g.E.g. time evolution of thetime evolution of thepartonic fireballpartonic fireball at temperature at temperature 1.7 T1.7 Tcc with with initialized initialized at at qq=0=0
W. Cassing, E. Bratkovskaya, PRC 78 (2008) 034919W. Cassing, E. Bratkovskaya, PRC 78 (2008) 034919W. Cassing, W. Cassing, EEPJ ST PJ ST 168168 (2009) (2009) 33
