Dileptons in heavy-ion-collisions

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1 Dileptons in heavy-ion-collisions Hendrik van Hees Goethe University Frankfurt and FIAS January 11, 018 Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

2 Outline 1 Heavy-ion collisions on one slide Electromagnetic probes Chiral symmetry and QCD phase diagram Electromagnetic radiation from hot/dense QCD matter Hadronic many-body theory 3 Bulk-medium evolution with transport and coarse graining coarse-graining in UrQMD 4 Dileptons in heavy-ion collisions Dielectrons (SIS/HADES) Dimuons (SPS/NA60) Dielectrons at RHIC Dielectrons at FAIR/RHIC-BES 5 Signatures of the QCD-phase structure? 6 Conclusions and Outlook Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, 018 / 46

Heavy-Ion collisions in a Nutshell theory of strong interactions: Quantum Chromo Dynamics, QCD GSI SIS: pp, dp, pa, AA collisions at low energies (E kin = 1.5-3.

3 Heavy-Ion collisions in a Nutshell theory of strong interactions: Quantum Chromo Dynamics, QCD GSI SIS: pp, dp, pa, AA collisions at low energies (E kin = GeV) Dielectrons from HADES CERN SPS: AA collisions with E kin = 158 GeV per nucleon on a fixed target (center-mass energy: s N N = 17.3 GeV) dileptons (particularly µ + µ in In-In collisions from NA60) BNL RHIC: Au Au collisions with center-mass energy of s N N = 00 GeV; beam-energy scan s N N = GeV dileptons from STAR and PHENIX; direct photons from PHENIX CERN LHC: Pb-Pb collisions at s =.76 TeV per nucleon direct photons from ALICE future experiments at CBM/FAIR and NICA: high µ B Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

4 Electromagnetic probes theory perspective Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

5 Vacuum Baseline: e + e hadrons u, d, s 3 loop pqcd Naive quark model R 1 1 Sum of exclusive Inclusive measurements measurements s(gev) R := σ e + e hadrons σ e +e µ + µ probes all hadrons with quantum numbers of γ R QM = N c f =u,d,s Q f = 3 [(/3) + ( 1/3) + ( 1/3) ] = Our aim pp l + l, pa l + l, AA l + l (l = e,µ) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

6 Hadron phenomenology and chiral symmetry QCD in light-quark sector (u, d, (s)): chiral symmetry in vacuum: Spontaneous breaking of chiral symmetry because q q 0 mass splitting of chiral partners qq-excitations of the QCD vacuum Energy (MeV) f1 (140) a1(160) f1(185) φ(0) f0( ) ρ (770) ω (78) P-S, V-A splitting in the physical vacuum π (140) Im Π V,A /(πs) [dim. less] V [τ > nπ ν τ ] A [τ > (n+1)π ν τ ] ρ(770) + cont. a 1 (160) + cont s [GeV ] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

7 The QCD-phase diagram hot and dense matter: quarks and gluons close together highly energetic collisions deconfinement quarks and gluons relevant dof quark-gluon plasma still strongly interacting fast thermalization! T [GeV] 0.5 quark-gluon plasma 0.0 RHIC qq = qq = 0 SPS 0.15 crit. point AGS hadron gas qq 0 SIS nuclei 0.0 µ N 1 st order qq 0 Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

The QCD-phase diagram at high temperature/density: restoration of chiral symmetry lattice QCD: T χ c T deconf c Mass mechanism of chiral restoration?

8 The QCD-phase diagram at high temperature/density: restoration of chiral symmetry lattice QCD: T χ c T deconf c Mass mechanism of chiral restoration? two main theoretical ideas dropping masses : m had ψψ melting resonances : broadening of spectra through medium effects More theoretical question: realization of chiral symmetry in nature? Spectral Function Spectral Function "ρ" "ρ" Dropping Masses? Melting Resonances? "a 1 " "a 1 " pert. QCD pert. QCD Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

9 Electromagnetic probes in heavy-ion collisions γ,l ± : no strong interactions reflect whole history of collision: from pre-equilibrium phase from thermalized medium QGP and hot hadron gas from VM decays after thermal freezeout dn ee / dydm π o,η Dalitz-decays ρ,ω Φ DD J/Ψ Ψ l π,... ρ/ω γ e e + Drell-Yan Low- Intermediate- High-Mass Region > fm > 1 fm < 0.1 fm mass [GeV/c ] Fig. by A. Drees γ Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

10 Electromagnetic probes from thermal source photon and dilepton thermal emission rates given by same electromagnetic-current-correlation function (J µ = f Q f ψ f γ µ ψ f ) McLerran-Toimela formula [MT85, GK91] q 0 dn γ d 4 x d 3 q = α em π g µν Im Π (ret) µν (q, u) f B (q u) q 0 = q dn e +e d 4 x d 4 q = g µν α Im 3q Π(ret) π3 µν (q, u) f B (q u) q =M e +e Lorentz covariant (dependent on four-velocity of fluid cell, u) q u = E cm : Doppler blue shift of q T spectra! to lowest order in α: 4παΠ µν Σ (γ) µν vector-meson dominance model: Σ γ µν = l + l -inv.-mass spectra in-med. spectral functions of vector mesons (ρ, ω, φ)! G ρ Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, 018 / 46

11 Radiation from thermal QGP: q q annihilation General: McLerran-Toimela formula dn (MT) l + l d 4 x d 4 q = α L(M ) g 3π 3 M µν Im Π µν em,i (M, q )f B (q u) i enumerates partonic/hadronic sources of em. currents in-medium em. current-current correlation function Π µν em,i = i d 4 x exp(iq x )Θ(x 0 ) j µ em,i (x ), j ν em,i (0) i in QGP phase: q q annihilation hard-thermal-loop improved em. current-current correlator q γ γ iπ em,qgp = q Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

12 Radiation from thermal sources: ρ decays model assumption: vector-meson dominance ρ γ l dn (MT) ρ l + l d 4 x d 4 q = M q 0 Γ ρ l + l (M ) dn ρ d 3 x d 4 q 4 mρ M = α 3π 3 L(M ) g ρ l + g µν ImD µν ρ (M, q )f B special case of McLerran-Toimela (MT) formula q u µπ (t ) T (t ) M = q : invariant mass, M, of dilepton pair L(M ) = (1 + m l /M ) 1 4m l /M : dilepton phase-space factor D µν ρ (M, q ): (four-transverse part of) in-medium ρ propagator at given T (t ), µ meson/baryon (t ) analogous for ω and φ Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

13 Transition form factors: ρ mesons via VMD π l l + γ V N l γ γ l l + γ P, S l + vector mesons have vacuum spectral shapes propagated as on-shell particles of finite lifetime and variable mass Dalitz decay: 1 particle 3 particles V : ω π + γ π + l + + l P, S: π,η γ + γ γ + l + + l R : Baryon resonances,n N + V N + γ N + l + + l vector-meson dominance model for hadron em. trans. FF R γ γ V hadronic hadronic Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

GiBUU: ρ meson in pp production through hadron resonances N N N R N N ρ, N N N N N πρ plots: J. Weil et al [WHM1, ABB + 14] VMD model em. transition form factors of baryon resonances!

14 GiBUU: ρ meson in pp production through hadron resonances N N N R N N ρ, N N N N N πρ plots: J. Weil et al [WHM1, ABB + 14] VMD model em. transition form factors of baryon resonances! ρ -line shape modified already in elementary hadronic reactions due to production mechanism via resonances Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

15 Hadronic many-body theory hadronic many-body theory (HMBT) for vector mesons [Ko et al, Chanfray et al, Herrmann et al, Rapp et al,...] ππ interactions and baryonic excitations effective hadronic models, implementing symmetries parameters fixed from phenomenology (photon absorption at nucleons and nuclei, πn ρn ) evaluated at finite temperature and density self-energies mass shift and broadening in the medium ρ π B *, a 1, K 1,... ρ ρ ρ π N, K, π,... Baryons important, even at low net baryon density n B n B reason: n B +n B relevant (CP inv. of strong interactions) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

16 Meson contributions 70 Im Σ ρ /m ρ [MeV] T=150MeV q=0.3gev ω sum a 1 K 1 h 1 π 0 f 1 30 sum Re Σ ρ /m ρ [MeV] 0 0 ω K 1 a M [GeV] [RG99] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

17 In-medium spectral functions and baryon effects [RW99] baryon effects important large contribution to broadening of the peak responsible for most of the strength at small M Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

18 Dilepton rates: Hadron gas QGP in-medium hadron gas matches with QGP similar results also for γ rates quark-hadron duality? [Rap13] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

19 Bulk-medium evolution Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

20 Bulk evolution with transport and coarse graining established transport models for bulk evolution e.g., UrQMD, GiBUU, BAMPS, (p)hsd,... solve Boltzmann equation for hadrons and/or partons dilemma: need medium-modified dilepton/photon emission rates usually available only in equilibrium QFT calculations ways out: use (ideal) hydrodynamics local thermal equilibrium use equilibrium rates use transport-hydro hybrid model: treat early stage with transport, then coarse grain switch to hydro switch back to transport (Cooper-Frye particlization ) here: UrQMD transport for entire bulk evolution use coarse graining in space-time cells extract T, µ B, µ π,... use equilibrium rates locally Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

21 Coarse-grained UrQMD (CGUrQMD) problem with medium modifications of spectral functions/interactions only available in equilibrium many-body QFT models use in-medium cross sections naively: double counting?!? way out: map transport to local-equilibrium fluid use ensemble of UrQMD runs with an equation of state space-time grid with t = 0. fm/c, x = 0.8 fm fit temperature, chemical potentials, flow-velocity field from anisotropic energy-momentum tensor [FMRS13] T µν = (ε + P )u µ u ν P g µν (P P )V µ V ν thermal rates from partonic/hadronic QFT become applicable here: extrapolated lattice QGP and Rapp-Wambach HMBT caveat: consistency between EoS, matter content of QFT model/urqmd! Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

22 Coarse-grained UrQMD (CGUrQMD) Temperature [MeV] T c = 170 MeV; T > T c lattice EoS; T < T c HRG EoS Lattice EoS (T =170 MeV) c Hadron Gas EoS (for µ =0) B Energy density ε/ε Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, 018 / 46 0

23 Coarse-grained UrQMD (CGUrQMD) pressure anisotropy (for SPS; NA60) 158 AGeV <dn ch /dη>=10 Central cell (x=y=z=0) 3 ) P P (GeV/fm Anisotropy parameter x Relaxation function r(x) Time t [fm] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

24 Dielectrons (SIS/HADES) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

25 CGUrQMD: Ar+KCl (1.76 AGeV) (SIS/HADES) coarse-graining method works at low energies! UrQMD-medium evolution + RW-QFT rates -1 ] dn/dm [GeV/c 1/N(π 0 ) Ar AGeV HADES acceptance, 0.1 < p < 1.1 GeV/c e (a) Coarse-Graining Medium ρ Medium ω Multi π UrQMD π η φ ρ ω fo fo M [GeV/c ] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

26 CGUrQMD: Ar+KCl (1.76 AGeV) (SIS/HADES) dielectron spectra from Ar + KCl(1.76 AGeV) e + e (SIS/HADES) m t spectra M ee < 0.13 GeV UrQMD (a) Ar AGeV πη /5 ] t [GeV/c dn/dm t ) 3/ )m Coarse-Graining Medium ρ Medium ω Multi π φ ρ ω fo fo < 0.13 GeV/c M ee 1/(N(π [GeV/c m t ] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

27 CGUrQMD: Ar+KCl (1.76 AGeV) (SIS/HADES) dielectron spectra from Ar + KCl(1.76 AGeV) e + e (SIS/HADES) m t spectra 0.13 GeVM ee < 0.3 GeV /5 t ] [GeV/c < M ee < 0.30 GeV/c -3 (b) dn/dm t ) 3/ )m 0 1/(N(π [GeV/c m t ] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

28 CGUrQMD: Ar+KCl (1.76 AGeV) (SIS/HADES) dielectron spectra from Ar + KCl(1.76 AGeV) e + e (SIS/HADES) m t spectra 0.3 GeVM ee < 0.45 GeV /5 ] t [GeV/c < M ee < 0.45 GeV/c -4 (c) dn/dm t ) 3/ )m 0 1/(N(π [GeV/c m t ] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

29 CGUrQMD: Ar+KCl (1.76 AGeV) (SIS/HADES) dielectron spectra from Ar + KCl(1.76 AGeV) e + e (SIS/HADES) m t spectra 0.45 GeVM ee < 0.65 GeV /5 ] t [GeV/c < M ee < 0.65 GeV/c -5 (d) dn/dm t ) 3/ )m 0 1/(N(π [GeV/c m t ] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

30 CGUrQMD: Ar+KCl (1.76 AGeV) (SIS/HADES) dielectron spectra from Ar + KCl(1.76 AGeV) e + e (SIS/HADES) m t spectra M ee > 0.65 GeV /5 ] t [GeV/c -4 M ee > 0.65 GeV/c -5 (e) dn/dm t ) 3/ )m 0 1/(N(π [GeV/c m t ] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

31 CGUrQMD: Ar+KCl (1.76 AGeV) (SIS/HADES) dielectron spectra from Ar + KCl(1.76 AGeV) e + e (SIS/HADES) m t spectra rapidity spectrum (M ee < 0.13 GeV) ) dn/dy 0 1/N(π (f) < 0.13 GeV/c M ee Radpidity y Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

32 CGUrQMD: Au+Au (1.3 AGeV) (SIS/HADES) [T. Galtyuk, Quark Matter 017 talk] good agreement between models and data consistency between two independent coarse-grained-urqmd simulations based on same Rapp-Wambach in-medium rates Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

33 Dimuons (SPS/NA60) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

34 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) ] -1 /dη) [0 MeV /dmdη)/(dn ch AGeV <dn ch /dη>=10, p > 0 GeV T HG-EoS + Lattice EoS In-medium ρ Non-thermal ρ QGP (Lattice) Multi π Sum (a) For comparison: Thermal ρ (no baryons) Perturb. qq µµ (dn M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

35 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) higher IMR: provides averaged true temperature T 1.5 GeV M.4 GeV = MeV clearly above T c MeV (no blueshifts in the invariant-mass spectra!) ] -1 /dη) [0 MeV /dmdη)/(dn ch (b) µµ (dn M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

36 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) p T < 0. GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (a) 158 AGeV <dn ch /dη>=10 < 0. GeV In-medium ρ Non-thermal ρ QGP (Lattice) Multi π Sum Invariant Mass M [GeV] p T Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

37 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 0. GeV < p T < 0.4 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (b) 0. < p T < 0.4 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

38 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 0.4 GeV < p T < 0.6 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (c) 0.4 < p T < 0.6 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

39 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 0.6 GeV < p T < 0.8 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (d) 0.6 < p T < 0.8 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

40 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 0.8 GeV < p T < 1.0 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (e) 0.8 < p T < 1.0 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

41 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 1.0 GeV < p T < 1. GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (f) 1.0 < p T < 1. GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

42 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 1. GeV < p T < 1.4 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (a) 1. < p T < 1.4 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

43 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 1.4 GeV < p T < 1.6 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (b) 1.4 < p T < 1.6 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

44 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 1.6 GeV < p T < 1.8 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (c) 1.6 < p T < 1.8 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

45 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) 1.8 GeV < p T <.0 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (d) 1.8 < p T <.0 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

46 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10).0 GeV < p T <. GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (e).0 < p T <. GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

47 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10). GeV < p T <.4 GeV ] -1 /dη) [0 MeV /dmdη)/(dn ch µµ (dn (f). < p T <.4 GeV Invariant Mass M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

48 t CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) ] t - /dη) [GeV dη)/(dn /dm ch (a) 158 AGeV HG-EoS + Lattice EoS <dn ch /dη>=10 0. < M < 0.4 GeV In-medium ρ Non-thermal ρ QGP (Lattice) Multi π Sum µµ )(dn (1/m m t -M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

49 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) t ] - t /dη) [GeV dη)/(dn /dm ch (b) 0.4 < M < 0.6 GeV µµ )(dn (1/m m t -M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

50 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) t ] - t /dη) [GeV dη)/(dn /dm ch (c) 0.6 < M < 0.9 GeV µµ )(dn (1/m m t -M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

51 CGUrQMD: In+In (158 AGeV) (SPS/NA60) dimuon spectra from In + In(158 AGeV) µ + µ (NA60) [EHWB15] min-bias data (dn ch /dy = 10) t ] - t /dη) [GeV dη)/(dn /dm ch (d) 1.0 < M < 1.4 GeV µµ )(dn (1/m m t -M [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

52 Dielectrons at RHIC Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

53 CGUrQMD: Au+Au ( s N N = 00 GeV) (RHIC/STAR) )] [1/(GeV/c dn/dm ee 1-1 e T e p > 0. GeV/c η < 1, y STAR data < 1 ee s = 00 AGeV (0-% centr.) Coarse-grained Rapp in-med ρ Rapp in-med ω Multi-pion QGP (Lattice) UrQMD π 0 η ω (fo) ρ (fo) φ [GeV/c ] M ee Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

54 CGUrQMD: Au+Au ( s N N = 00 GeV) (RHIC/PHENIX) )] in PHENIX acc. [1/(GeV/c s = 00 AGeV (0-% centr.) e p > 0. GeV/c Coarse-grained UrQMD T e y < 1, Θ ee > 0.1 rad Rapp in-med ρ π 0 PHENIX HBD data Rapp in-med ω η Multi-pion ω (fo) QGP (Lattice) ρ (fo) φ dn/dm ee [GeV/c ] M ee Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

55 Dielectrons at RHIC-BES/FAIR/NICA Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

56 CGUrQMD: Au+Au (E lab = -35 AGeV) NB: also photon spectra [EHB16b] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

57 Signatures of the QCD-phase structure? Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

58 QCD phase structure from em. probes? hadronic observables like p T spectra: snapshot of the stage after kinetic freezeout particle abundancies: chemical freezeout em. probes: emitted during the whole medium evolution life time of the medium four-volume of the fireball use CGUrQMD to study system-size dependence study AA collisions for different A [EHWB15] excitation functions : systematics of l + l (and γ) emission vs. beam energy [EHB16b, RH16] similar study in [GHR + 16] caveat: phase transition not really implemented!!! Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

59 Scaling behavior of thermal-dilepton yield central collisions from C+C to Au+Au at E kin = 1.76 AGeV 1 1 C C /Ratio AA Ratio thermal e e Yield 0. < M < 0.4 GeV 4/3 A + - thermal e e Yield 0. < M < 0.4 GeV thermal V thermal e e Yield 0. < M < 0.4 GeV thermal A t + - thermal e e Yield 0. < M < 0.4 GeV 4/3 N π 0 (b) Mass number A thermal-dilepton yield roughly V (4) therm A4/3 At therm N 4/3 π 0 at low(est) beam energies: lifetime of medium ˆ= time nuclei pass through each other Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

60 Mass-temperature relation in dilepton emission interplay between increasing volume and decreasing temperature of fireball in IMR (T < m φ < M l +l < m J /ψ) biased towards early hot stages only background : correlated D D decays, some Drell-Yan otherwise emission from thermal QGP and hadronic sources invariant-mass slope true invariant space-time averaged temperature no blueshift due to radial flow as in p t spectra (e.g., photons) ] -1 dn e + e -/dt [GeV AGeV (0-% centr.) [EHB16b, EHB16a] M < 0. GeV/c 0. < M < 0.6 GeV/c 0.6 < M < 0.9 GeV/c M > 1.1 GeV/c Temperature T [GeV] Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

61 Dilepton systematics in the beam-energy scan thermal-fireball model [RH16, EHB16a] invariant-mass slope in IMR true temperature! no blue shift from radial flow as in p T /m T spectra Central AA Collisions T (MeV) T s (M= GeV) T i T pc 0 s 1/ (GeV) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

62 Dilepton systematics in the beam-energy scan thermal-fireball model [RH16] beam-energy scan at RHIC and lower energies at FAIR and dilepton yield as fireball-lifetime clock 5 0 hadronic QGP sum sum (acc) 3.75 τ fb 0.3GeV < M < 0.7GeV 0 15 N l + l /Nch τfb(fm/c) 0 0 snn (GeV) 0 Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

63 Conclusions and Outlook General ideas em. probes in-medium em. current-correlation function dual rates around T c (compatible with χ symmetry restoration) medium modifications of ρ, ω, φ importance of baryon-resonance interactions Application to dileptons in HICs Outlook coarse-grained transport (here: CGUrQMD) allows use of thermal-qft spectral VM functions applicable also at low collision energies allows use of thermal-qft models for dilepton rates successful description from SIS to RHIC energies consistent description of M and m T spectra! effective slope of M spectra (1.5 GeV < M < M J /ψ ) provides T beam-energy scan at RHIC and FAIR signature of phase transition? signature of cross-over vs. 1st order (or even critical endpoint)??? challenge: phase transition in (coarse-grained) transport??? Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

64 Bibliography I [ABB + 14] [EHB16a] [EHB16b] G. Agakishiev, et al., Baryon resonance production and dielectron decays in proton-proton collisions at 3.5 GeV, Eur. Phys. J. A 50 (014) 8. S. Endres, H. van Hees, M. Bleicher, Energy, centrality and momentum dependence of dielectron production at collider energies in a coarse-grained transport approach, Phys. Rev. C 94 (016) S. Endres, H. van Hees, M. Bleicher, Photon and dilepton production at the Facility for Proton and Anti-Proton Research and beam-energy scan at the Relativistic Heavy-Ion Collider using coarse-grained microscopic transport simulations, Phys. Rev. C 93 (016) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

65 Bibliography II [EHWB15] S. Endres, H. van Hees, J. Weil, M. Bleicher, Dilepton production and reaction dynamics in heavy-ion collisions at SIS energies from coarse-grained transport simulations, Phys. Rev. C 9 (015) [FMRS13] [GHR + 16] [GK91] W. Florkowski, M. Martinez, R. Ryblewski, M. Strickland, Anisotropic hydrodynamics, Nucl. Phys. A (013) 803c. T. Galatyuk, P. M. Hohler, R. Rapp, F. Seck, J. Stroth, Thermal Dileptons from Coarse-Grained Transport as Fireball Probes at SIS Energies, Eur. Phys. J. A 5 (016) C. Gale, J. I. Kapusta, Vector dominance model at finite temperature, Nucl. Phys. B 357 (1991) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

66 Bibliography III [MT85] [Rap13] L. D. McLerran, T. Toimela, Photon and Dilepton Emission from the Quark-Gluon Plasma: Some General Considerations, Phys. Rev. D 31 (1985) R. Rapp, Dilepton Spectroscopy of QCD Matter at Collider Energies, Adv. High Energy Phys. 013 (013) [RG99] R. Rapp, C. Gale, ρ properties in a hot meson gas, Phys. Rev. C 60 (1999) [RH16] [RW99] R. Rapp, H. van Hees, Thermal Dileptons as Fireball Thermometer and Chronometer, Phys. Lett. B 753 (016) R. Rapp, J. Wambach, Low mass dileptons at the CERN-SPS: Evidence for chiral restoration?, Eur. Phys. J. A 6 (1999) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

67 Bibliography IV [WHM1] J. Weil, H. van Hees, U. Mosel, Dilepton production in proton-induced reactions at SIS energies with the GiBUU transport model, Eur. Phys. J. A 48 (01) Hendrik van Hees (GU Frankfurt/FIAS) Dileptons in HICs January 11, / 46

Dileptons with a coarse-grained transport approach

Dileptons with a coarse-grained transport approach Hendrik van Hees Goethe University Frankfurt and FIAS July 19, 017 in collaboration with S. Endres, J. Weil, M. Bleicher Hendrik van Hees (GU Frankfurt/FIAS)