Heavy Ion Theory Review Raju Venugopalan Brookhaven National

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 ² How is entropy produced and what is the nature of the matter produced ? ² How does strongly correlated matter evolve ? ² How do hard probes (jets, Onia, …) interact with the matter ? ² 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 ² How is entropy produced and what is the nature of the matter produced ? ² How does strongly correlated matter evolve ? ² How do hard probes (jets, Onia, …) interact with the matter ? ² 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, PLB 706 (2011)219 Energy evolution of multi-gluon correlators (on sat. scale ~ 1/Q S ) 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 Te. V: possibly stringent tests from multiple final states

Gluon saturation and CGC: Strong hints Theory: Albacete et al. 1203. 1043 Theory: Tribedy, RV, 1112. 2445 d-Au di-hadron to p+p ratio HERA e+p cross-sections p+p Theory: Stasto, Xiao, Yuan, 1109. 1817 Theory: Dusling, RV, 1201. 2658 PHENIX, PRL 107, 172301 (2011) CMS p+p ridge

Gluon saturation and CGC: p+Pb constraints Albacete, Dumitru, Fujii, Nara, 1209. 2001

The 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 Φ 4 Dusling, Epelbaum, Gelis, RV, ar. Xiv: 1206. 3336 (arb. lattice units) Decoherence EOS Isotropization

Proof of concept: isotropization of longitudinally expanding fields in scalar Φ 4 Dusling, Epelbaum, Gelis, RV, ar. Xiv: 1206. 3336 (arb. lattice units) Quantum fluctuations generate an anomalously low viscosity

Hydrodynamics from quantum fields: 1/αS τ ~ 1/QS τ >> 1/QS 1/αS f(p) ΛS=Λ=QS p ΛS Λ Thermal on long time scales τ ≈(1/αS)2 1/QS : Λ =T, m 2 = 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 p. T < M, long range rapidity corr. ? p

The first fermi: a master formula Also correlators of Tμν ü From solutions of B-JIMWLK ² Gauge invariant Gaussian spectrum of quantum fluctuations ü 3+1 -D solutions of Yang-Mills equations ² Expression computed recently-numerical evaluation in progress Dusling, Epelbaum, Gelis, RV u This is what needs to be matched to viscous hydrodynamics, event-by-event u 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

Heavy Ion phenomenology: IP-Glasma model I) Multiplicity distributions + Schenke, Tribedy, RV: PRL 108 (2012), 252301; ar. Xiv: 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 RHIC and LHC have ~ 70% different η/s Niemi et al PRL 106 (2011)

Heavy Ion phenomenology: IP-Glasma model Event-by-event flow distributions vn distributions track eccentricities εn spatial fluctuations efficiency => perfect fluidity momentum anisotropies + Gale, Jeon, Schenke, Tribedy, RV, 1209. 6330

P Flow moments: analogy with the Early Universe Mishra et al; Mocsy- Sorensen HIC The Universe kinetic freeze-out lumpy initial energy density distributions and correlations of produced particles hadronization QGP phase quark and gluon degrees of freedom Credit: NASA Δρ/√ρref Δφ WMAP ISMD Hiroshima, Japan: September, 2011 HIC-ALICE

Jet probes of strongly correlated QGP J. Milhano, QM 12 talk Ø Radiative energy loss Ø Broadening due to multiple Scattering & El. Scat. Energy loss Ø Modification of color correlations

Jet probes of strongly correlated QGP J. Milhano, QM 12 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 Ge. V!

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

Jet probes of strongly correlated QGP Milhano Simple p. QCD model based on soft gluons kicked out of shower by mult. scatt. consistent with di-jet data on x= pt 1/pt 2 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, Ya. JEM

Quarkonium probes of strongly correlated QGP (1 S) Onium regeneration models give good description of LHC data Important ingredient: Im V(r) -- recent progress in NRQCD models -- Ad. S & Latt. models show similar trends See, for eg. , T. Hatsuda, QM 12 plenary (2 S) Rapp et al. , QM 2012

Topology of excited vacuum: Chiral Magnetic Effect Kharzeev, Mc. Lerran, Warringa, NPA (2008) Sphaleron transitions in external B field can lead to induced charge separation – Chiral Magnetic Effect N C S = 2 Conventional explanations (charge conservation + v 2) exist… - Pratt, Schlichting

Topology of excited vacuum: Chiral Magnetic Effect 70 -80% N C S = 0 -1% spectator neutrons Effect disappears with B field… but v 2 is 2. 5% 2 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 Me. V (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 ² How is entropy produced and what is the nature of the matter produced ? ² How does strongly correlated matter evolve ? ² How do hard probes (jets, Onia, …) interact with the matter ? ² 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 !!