Heavy Ion Theory Review Raju Venugopalan Brookhaven National Laboratory LHC week in Split, October 1-6, 2012

Heavy Ion Theory (Selective) Review Raju Venugopalan Brookhaven National Laboratory LHC week in Split, October 1-6, 2012

Some key questions in heavy ion physics How is entropy produced and what is the nature of the matter produced ? How does strongly correlated matter evolve ? How do hard probes (jets, Onia,…) interact with the matter ? What can we learn about how emergent features (topological, chiral) of QCD with varying T, μB and B ?

Some key questions in heavy ion physics How is entropy produced and what is the nature of the matter produced ? How does strongly correlated matter evolve ? How do hard probes (jets, Onia,…) interact with the matter ? What can we learn about how emergent features (topological, chiral) of QCD with varying T, μB and B ? Close analogies to key issues in strongly correlated electron systems, Bose-Einstein condensates, early universe cosmology (inflation and hot era), plasma physics, chaotic dynamical systems, classical and quantum gravity

Multi-particle production: saturated wave-functions Incoming nuclei are Color Glass Condensates: Highly occupied gluon states with maximal occupancy allowed in QCD

Multi-particle production: saturated wave-functions Dumitru,Jalilian-Marian,Lappi,Schenke,RV, PLB706 (2011)219 Energy evolution of multi-gluon correlators (on sat. scale ~ 1/QS ) test fundamental features of QCD in deeply non-linear regime

Gluon saturation and CGC: Strong hints i) Good agreement of saturation models with combined HERA data for x < 0.01 ii) Hadron correlations in deuteron-gold collisions at RHIC iii) Bulk features of LHC pp data iv) CMS “ridge” – di-hadron correlations in high multiplicity p+p Upcoming p+Pb at 5 TeV: possibly stringent tests from multiple final states

Gluon saturation and CGC: Strong hints Theory:Tribedy, RV, 1112.2445 Theory: Albacete et al. 1203.1043 HERA e+p cross-sections p+p Theory: Stasto,Xiao,Yuan, 1109.1817 Theory: Dusling, RV, 1201.2658 d-Au di-hadron to p+p ratio PHENIX, PRL107, 172301 (2011) CMS p+p ridge

Gluon saturation and CGC: p+Pb constraints Albacete,Dumitru,Fujii,Nara,1209.2001

The Glasma Glasma (\Glaahs-maa\): Noun: non-equilibrium matter between CGC and QGP Solutions of Yang-Mills equations produce (nearly) boost invariant gluon field configurations: “Glasma flux tubes” Lumpy gluon fields color screened over transverse distances ~ 1/QS - Convolution of NBD multiplicity distributions. Glue configurations very unstable to quantum fluctuations & grow exponentially -- important mechanism for early isotropization

Proof of concept: isotropization of longitudinally expanding fields in scalar Φ4 Dusling,Epelbaum,Gelis,RV, arXiv:1206.3336 (arb. lattice units) Decoherence EOS Isotropization

Proof of concept: isotropization of longitudinally expanding fields in scalar Φ4 Dusling,Epelbaum,Gelis,RV, arXiv:1206.3336 (arb. lattice units) Quantum fluctuations generate an anomalously low viscosity

Hydrodynamics from quantum fields: τ ~ 1/QS f(p) p ΛS Λ 1/αS τ >> 1/QS 1/αS p ΛS=Λ=QS f(p) Thermal on long time scales τ ≈(1/αS)2 1/QS : Λ =T, m2 = Λ ΛS (electric screening), ΛS = αST (magnetic screening) Isotropization (and hydrodynamics) can take place on very short time scales ~ 1/QS Interplay of isotropization vs thermalization: extract from photon spectra + flow, di-leptons for pT < M, long range rapidity corr. ?

The first fermi: a master formula increasing seed size 2500 Also correlators of Tμν From solutions of B-JIMWLK Gauge invariant Gaussian spectrum of quantum fluctuations 3+1-D solutions of Yang-Mills equations Expression computed recently-numerical evaluation in progress Dusling,Epelbaum,Gelis,RV This is what needs to be matched to viscous hydrodynamics, event-by-event All modeling of initial conditions for heavy ion collisions includes various degrees of over simplification relative to this “master” formula

IP-Glasma model: match event-by-event Yang-Mills to viscous hydro 2+1-D Yang-Mills + 2+1-D Viscous hydro 2+1-D Yang-Mills

Heavy Ion phenomenology: IP-Glasma model I) Multiplicity distributions Schenke,Tribedy,RV: PRL108 (2012), 252301; arXiv:1206.6805 +

IP-Glasma model II) Harmonic flow moments (2+1-D CYM + viscous hydro a la MUSIC) MUSIC:Schenke,Jeon,Gale (2011) + - Gale,Jeon,Schenke,Tribedy,RV, 1209.6330 + -

IP-Glasma model Temperature dependent η/s Niemi et al PRL106 (2011) RHIC and LHC have ~ 70% different η/s

Heavy Ion phenomenology: IP-Glasma model Gale,Jeon,Schenke,Tribedy,RV, 1209.6330 Event-by-event flow distributions vn distributions track eccentricities εn spatial fluctuations efficiency => perfect fluidity momentum anisotropies +

Flow moments: analogy with the Early Universe P Flow moments: analogy with the Early Universe Mishra et al; Mocsy- Sorensen The Universe HIC QGP phase quark and gluon degrees of freedom hadronization kinetic freeze-out lumpy initial energy density distributions and correlations of produced particles Credit: NASA Δρ/√ρref Δφ WMAP HIC-ALICE

Jet probes of strongly correlated QGP J. Milhano, QM12 talk Radiative energy loss Broadening due to multiple Scattering & El. Scat. Energy loss Modification of color correlations

Jet probes of strongly correlated QGP J. Milhano, QM12 talk is a measure of the transport properties of the medium In kinetic theory, Majumder,Muller,Wang (2007) Independent measurements of l.h.s & r.h.s test simple quasi-particle pictures

Jet probes of strongly correlated QGP Remarkable pattern of suppression up to 300 GeV!

Jet probes of strongly correlated QGP AdS/CFT Two extremes for Jet-Medium interactions pQCD Fragmentation functions and differential jet shapes At the LHC, jets retain shape but significant radiation outside cone

Jet probes of strongly correlated QGP Milhano Simple pQCD model based on soft gluons kicked out of shower by mult. scatt. consistent with di-jet data on x= pt1/pt2 and z

Jet probes of strongly correlated QGP Problem: medum modification of parton shower Recent progress: in medium splitting has probabilistic interpretation Mehtar-Tani, Salgado,Tywoniuk, 1205. 5739 Casalderrey-Solana,Iancu,1105.1760 Blaizot,Dominguez,Iancu,Mehtar-Tani,1209.4585 Implement in MCs: HIJING,Q-PYTHIA,Q-HERWIG,JEWELL,YaJEM

Quarkonium probes of strongly correlated QGP Onium regeneration models give good description of LHC data (2S) Important ingredient: Im V(r) -- recent progress in NRQCD models -- AdS & Latt.models show similar trends Rapp et al., QM2012 See, for eg., T. Hatsuda, QM12 plenary

Topology of excited vacuum: Chiral Magnetic Effect Kharzeev,McLerran,Warringa, NPA (2008) Sphaleron transitions in external B field can lead to induced charge separation – Chiral Magnetic Effect NCS = -2 -1 0 1 2 Conventional explanations (charge conservation + v2) exist… Pratt,Schlichting

Topology of excited vacuum: Chiral Magnetic Effect NCS = -2 -1 0 1 2 70-80% 0-1% spectator neutrons Effect disappears with B field… but v2 is 2.5% Very preliminary, but if confirmed would be spectacular… Corollary: isotropization may also proceed through sphaleron decay Shuryak RV

QCD at finite μB Chiral transition μB=0: Tc=154±9 / 157±6 MeV (hot QCD/ Wuppertal-Budapest) Some chiral models predict negative Kurtosis as signature of Critical End Point Also negative χ6 / χ2 Exciting potential of RHIC high statistics BES !

Recap: key questions in heavy ion physics How is entropy produced and what is the nature of the matter produced ? How does strongly correlated matter evolve ? How do hard probes (jets, Onia,…) interact with the matter ? What can we learn about how emergent features (topological, chiral) of QCD with varying T, μB and B ? We are making empirical progress on all these fronts, but… there’s a long way to go before we can claim to understand the complex collective dynamics of the only accessible non-Abelian Field Theory

In the meanwhile, Happy 75 birthday, Guy !!