EM Radiation + Heavy Flavor in Heavy-Ion Collisions 7/19/2018 Ralf Rapp Cyclotron Institute + Dept of Phys & Astro Texas A&M University College Station, USA EMMI Workshop on “Prospects + Challenges for Future Experiments in HICs” GSI (Darmstadt, Germany), 15.+16.02.13

1.) Intro: EM Radiation + HQ Transport e+e- → hadrons: Im Pem(M) / M2 Heavy-Quark Potential V [½GeV] M [GeV] r [½fm] Im Πem(M,q;mB,T) in-medium transport coefficients Modifications of light resonances: transition to QGP? Basic QCD force in QGP + at hadronization? Q e+ e- r well-defined baselines

2.1 EM Radiation and Chiral Phase Transition ≈ qq / qq0 - - Tpcc ~155MeV [Fodor et al ’10] [Gerber+Leutwyler ‘89, Karsch,Redlich+Tawfik ‘05] hadron resonance gas chiral restoration in “hadronic phase”? (low-mass dileptons!)

2.2 Chiral Condensate + r-Meson Broadening qq / qq0 - - effective hadronic theory h = mq h|qq|h > 0 contains quark core + pion cloud = Shcore + Shcloud ~ + + matches spectral medium effects: resonances + pion cloud resonances + chiral mixing drive r-SF toward chiral restoration Sp > - r

2.3 QCD + Weinberg Sum Rules in Medium [Hatsuda+Lee’91, Asakawa+Ko ’93, Klingl et al ’97, Leupold et al ’98, Kämpfer et al ‘03, Ruppert et al ’05] [Weinberg ’67, Das et al ’67; Kapusta+Shuryak ‘94] T [GeV] melting scenario quantitatively compatible with chiral restoration microscopic calculation of in-medium axialvector to be done [Hohler et al ‘12] s [GeV2] rV,A/s Vacuum T=140MeV T=170MeV

2.4 Dilepton Spectro-Thermo-Meter at SPS Invariant Rate vs. M-Spectra Transverse-Momentum Spectra cont. Tc=160MeV Tc=190MeV r Low mass: radiation from around T ~ Tpcc ~ 150MeV Intermediate mass: T ~ 170 MeV and higher Consistent with pT slopes: Teff ~ T + M (bflow)2

2.5 e+e- Excitation Function: SPS - RHIC Pb-Au(8.8GeV) Au-Au (20-200GeV) QM12 Pb-Au(17.3GeV) no apparent change of the excess emission source suggests “universal” medium effect around Tpc caveat: PHENIX central; FAIR,LHC? [cf. also Bratkovskaya et al, Alam et al, Bleicher et al …]

2.6.1 Direct Photons at RHIC Spectra Elliptic Flow ← excess radiation total [van Hees, Gale+RR ’11] Teffexcess = (220±25) MeV flow blue-shift: Teff ~ T √(1+b)/(1-b) , b~0.3: T ~ 220/1.35 ~ 160 MeV small slope + large v2 suggest main emission around Tpc

2.6.2 Direct Photons at LHC Spectra Elliptic Flow ● ALICE [van Hees et al in prep] similar to RHIC results (not enough v2) larger (non-pert.) photon emission rates around Tpc? other explanations…?

3.) Heavy Flavor in Medium Large scale mQ >> T, LQCD , coupled to non-perturbative environment Open Heavy Flavor: Hadronization: mQ >> Tpc - heavy flavor individually conserved through transition - hadron formation with light-quark content of QGP - (pre-) resonant Qq correlations above Tpc Diffusion - same interaction operative as in hadronization - dominated by elastic scattering → friction + diffusion coefficients D c

3.1 Heavy-Quark Transport and Spectral Function p2 ~ mQ T >> k2 ~ T2  Brownian Motion: Q Fokker Planck Eq. thermalization rate diffusion coefficient Scattering amplitude (non-pert. driving kernel!) Scattering rate (self-energy) → spectral function (propagator)

3.2 Heavy Quarkonia in Medium Field-theoretic potential approach effective propagator: Coulomb + string fit to lattice-QCD free energy [Megias et al ‘07] In-Medium Q-Q T-Matrix: - - Q-Q propagator:

3.3 Quarkonium Spectral Functions + Correlators [Aarts et al ‘07] limiting cases: assume V=U or F [Satz et al ’01+’08, Mocsy+Petreczky ’05+’08, Wong ’06, Cabrera,Riek+RR ’06+’10, Beraudo et al ’06, Lee et al ’09, …]

→ ← - 3.4 Quarkonium Transport J/y + q,g c + c + X - D J/y c Rate Equation for J/y + q,g c + c + X J/y D - c reaction rate equilibrium limit (y -width) in-med properties: spectral function, encodes screening/dissociation formation sensitive to HQ distributions [cf. also Andronic et al, Zhuang et al, Ferreiro et al, …]

3.5 Back to Open Heavy Flavor - heavy-light T-matrix → HQ transport “Feshbach” resonances (hadronization!) c-q Thermalization Rate gc [1/fm] factor 3-4 faster than pert. QCD marked 3-momentum dependence

3.6 Charm + Bottom Transport at RHIC +LHC Min Bias Pb-Pb 2.76TeV B-meson (non-prompt J/y) ■ CMS preliminary strangeness enhancement exhibits HQ interactions [He et al ’12] [see also van Hees et al, Gossiaux et al, Uphoff et al,…]

4.) Conclusions Low-mass dileptons (+photons) probe the matter formed in URHICs around Tpc (mass shape+slopes, excitation fct, photon-v2) Theory studies combining chiral hadronic models + sum rules Heavy flavors probe QGP diffusion + hadronization, possibly dominated by same non-perturbative interaction Self-consistent / unified approach to HQ + quarkonium transport EM Radiation + Heavy-Flavor remain premier tools to study non-perturbative properties of QCD matter at future HI facilities

Outline 2.) Spectral Function + Emission Temperature 7/19/2018 2.) Spectral Function + Emission Temperature  In-Medium r + Dilepton Rates  Dilepton Mass Spectra + Slopes  Excitation Function + Elliptic Flow 3.) Chiral Symmetry Restoration  Chiral Condensate  Weinberg + QCD Sum Rules  Euclidean Correlators 4.) Conclusions

3.4 Vector Correlator in Thermal Lattice QCD Euclidean Correlation fct. Lattice (quenched) [Ding et al ‘10] Hadronic Many-Body [RR ‘02] “Parton-Hadron Duality” of lattice and in-medium hadronic?

4.2 Low-Mass e+e- at RHIC: PHENIX vs. STAR PHENIX enhancement (central!) not accounted for by theory STAR data ok with theory (charm?!)

2.3 QCD Sum Rules: r and a1 in Vacuum dispersion relation: [Shifman,Vainshtein+Zakharov ’79] lhs: hadronic spectral fct. rhs: operator product expansion 4-quark + gluon condensate dominant vector axialvector

2.3 Dilepton Rates vs. Exp.: NA60 “Spectrometer” Evolve rates over fireball expansion: Acc.-corrected m+m- Excess Spectra In-In(17.3GeV) [NA60 ‘09] [van Hees+RR ’08] Mmm [GeV] invariant-mass spectrum directly reflects thermal emission rate!

4.5 QGP Barometer: Blue Shift vs. Temperature SPS RHIC QGP-flow driven increase of Teff ~ T + M (bflow)2 at RHIC high pt: high T wins over high-flow r’s → minimum (opposite to SPS!) saturates at “true” early temperature T0 (no flow)

4.3.2 Revisit Ingredients Emission Rates Fireball Evolution Hadron - QGP continuity! conservative estimates… multi-strange hadrons at “Tc” v2bulk fully built up at hadronization chemical potentials for p, K, … [Turbide et al ’04] [van Hees et al ’11]

4.1.3 Mass Spectra as Thermometer Emp. scatt. ampl. + T-r approximation Hadronic many-body Chiral virial expansion Thermometer [NA60, CERN Courier Nov. 2009] Overall slope T~150-200MeV (true T, no blue shift!)

4.1.2 Sensitivity to Spectral Function In-Medium r-Meson Width Mmm [GeV] avg. Gr (T~150MeV) ~ 370 MeV  Gr (T~Tc) ≈ 600 MeV → mr driven by (anti-) baryons

5.2 Chiral Restoration Window at LHC low-mass spectral shape in chiral restoration window: ~60% of thermal low-mass yield in “chiral transition region” (T=125-180MeV) enrich with (low-) pt cuts

4.3 Dimuon pt-Spectra and Slopes: Barometer Effective Slopes Teff theo. slopes originally too soft increase fireball acceleration, e.g. a┴ = 0.085/fm → 0.1/fm insensitive to Tc=160-190MeV

2.3.2 NA60 Mass Spectra: pt Dependence Mmm [GeV] more involved at pT>1.5GeV: Drell-Yan, primordial/freezeout r , …

3.4.2 Back to Spectral Function suggests approach to chiral restoration + deconfinement

4.4 Elliptic Flow of Dileptons at RHIC maximum structure due to late r decays [He et al ‘12] [Chatterjee et al ‘07, Zhuang et al ‘09]

4.2 Low-Mass Dileptons: Chronometer In-In Nch>30 first “explicit” measurement of interacting-fireball lifetime: tFB ≈ (7±1) fm/c

4.1 Quantitative Bulk-Medium Evolution initial conditions (compact, initial flow?) EoS: lattice (QGP, Tc~170MeV) + chemically frozen hadronic phase spectra + elliptic flow: multistrange at Tch ~ 160MeV p, K, p, L, … at Tfo ~ 110MeV v2 saturates at Tch, good light-/strange-hadron phenomenology [He et al ’11]

4.4.3 Origin of the Low-Mass Excess in PHENIX? QGP radiation insufficient: space-time , lattice QGP rate + resum. pert. rates too small must be of long-lived hadronic origin Disoriented Chiral Condensate (DCC)? Lumps of self-bound pion liquid? Challenge: consistency with hadronic data, NA60 spectra! [Bjorken et al ’93, Rajagopal+Wilczek ’93] - “baked Alaska” ↔ small T - rapid quench+large domains ↔ central A-A - ptherm + pDCC → e+ e- ↔ M~0.3GeV, small pt [Z.Huang+X.N.Wang ’96 Kluger,Koch,Randrup ‘98]

4.7.2 Light Vector Mesons at RHIC + LHC baryon effects important even at rB,tot= 0 : sensitive to rBtot= rB + rB (r-N and r-N interactions identical) w also melts, f more robust ↔ OZI - -

5.3 Intermediate Mass Emission: “Chiral Mixing” [Dey, Eletsky +Ioffe ’90] low-energy pion interactions fixed by chiral symmetry = mixing parameter degeneracy with perturbative spectral fct. down to M~1GeV physical processes at M≥ 1GeV: pa1 → e+e- etc. (“4p annihilation”)

3.2 Dimuon pt-Spectra and Slopes: Barometer pions: Tch=175MeV a┴ =0.085/fm pions: Tch=160MeV a┴ =0.1/fm modify fireball evolution: e.g. a┴ = 0.085/fm → 0.1/fm both large and small Tc compatible with excess dilepton slopes

2.3.3 Spectrometer III: Before Acceptance Correction emp. ampl. + “hard” fireball hadr. many-body + fireball schem. broad./drop. + HSD transport chiral virial + hydro Discrimination power much reduced can compensate spectral “deficit” by larger flow: lift pairs into acceptance

4.1 Nuclear Photoproduction: r Meson in Cold Matter g + A → e+e- X extracted “in-med” r-width Gr ≈ 220 MeV e+ e- Eg≈1.5-3 GeV g r [CLAS+GiBUU ‘08] Microscopic Approach: Fe - Ti g N r product. amplitude in-med. r spectral fct. + M [GeV] [Riek et al ’08, ‘10] full calculation fix density 0.4r0 r-broadening reduced at high 3-momentum; need low momentum cut!

3.5 Summary: Criteria for Chiral Restoration Vector (r) – Axialvector (a1) degenerate [Weinberg ’67, Das et al ’67] pQCD QCD sum rules: medium modifications ↔ vanishing of condensates Agreement with thermal lattice-QCD Approach to perturbative rate (QGP)

2.2 Dilepton Rates: Hadronic - Lattice - Perturbative dRee /dM2 ~ ∫d3q f B(q0;T) Im Pem continuous rate through Tpc 3-fold “degeneracy” toward ~Tpc - [qq→ee] [HTL] [Ding et al ’10] dRee/d4q 1.4Tc (quenched) q=0 [RR,Wambach et al ’99]

3.2 Spectral Functions + Weinberg Sum Rules Quantify chiral symmetry breaking via observable spectral functions Vector (r) - Axialvector (a1) spectral splitting [Weinberg ’67, Das et al ’67; Kapusta+Shuryak ‘93] t→(2n+1)p pQCD Updated “fit”: [Hohler+RR ‘12] r + a1 resonance, excited states (r’+ a1’), universal continuum (pQCD!) t→(2n)p [ALEPH ’98,OPAL ‘99] rV/s rA/s