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

Heavy Ion Theory Review

Raju VenugopalanBrookhaven National Laboratory

LHC week in Split, October 1-6, 2012

Heavy Ion Theory (Selective) Review

Raju VenugopalanBrookhaven 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 ?




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

Energy evolution of multi-gluon correlators (on sat. scale ~ 1/QS ) test fundamental features of QCD in deeply non-linear regime

Dumitru,Jalilian-Marian,Lappi,Schenke,RV, PLB706 (2011)219

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

p+pHERA e+p cross-sections

PHENIX, PRL107, 172301 (2011)

d-Au

di-h

adro

n to

p+p

ratio

Theory: Albacete et al. 1203.1043 Theory:Tribedy, RV, 1112.2445

Theory: Dusling, RV, 1201.2658

Theory: Stasto,Xiao,Yuan, 1109.1817

CMS p+p ridge

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

The GlasmaGlasma (\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

1/αS

pΛS=Λ=QS

τ >> 1/QS

f(p)

pΛS Λ

1/αS

Thermal on long time scales τ ≈(1/αS)2 1/QS : Λ =T, m2 = Λ ΛS (electric screening), ΛS = αST (magnetic screening)

f(p)

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

Gauge invariant Gaussian spectrum of quantum fluctuations

From solutions of B-JIMWLK

3+1-D solutions of Yang-Mills equations

Also correlators of Tμν

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

2+1-D Yang-Mills2+1-D Yang-Mills + 2+1-D Viscous hydro

IP-Glasma model: match event-by-event Yang-Mills to viscous hydro

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

+

IP-Glasma model

Gale,Jeon,Schenke,Tribedy,RV, 1209.6330

II) Harmonic flow moments (2+1-D CYM + viscous hydro a la MUSIC)

+-

MUSIC:Schenke,Jeon,Gale (2011)

IP-Glasma modelTemperature dependent η/s Niemi et al PRL106 (2011)

RHIC and LHC have ~ 70% different η/s

Heavy Ion phenomenology: IP-Glasma modelGale,Jeon,Schenke,Tribedy,RV, 1209.6330

+

Event-by-event flow distributions

vn distributions track eccentricities εn

spatial fluctuations

efficiency => perfect fluidity

momentum anisotropies

ISMD Hiroshima, Japan: September, 2011

P

WMAPHIC-ALICE

Credit: NASA

The Universe HIC

QGP phasequark and gluon degrees of freedom

hadronization

kineticfreeze-out

lumpy initial energy density

distributions and correlations of

produced particles

Flow moments: analogy with the Early Universe

Δφ

Δρ/√ρref

Mishra et al; Mocsy- Sorensen

Jet probes of strongly correlated QGPJ. Milhano, QM12 talk

Radiative energy loss Broadening due to multiple Scattering & El. Scat. Energy loss Modification of color correlations

Jet probes of strongly correlated QGPJ. Milhano, QM12 talk

is a measure of the transport properties of the medium

In kinetic theory, Independent measurements of l.h.s & r.h.s test simple quasi-particle pictures

Majumder,Muller,Wang (2007)

Jet probes of strongly correlated QGP

Remarkable pattern of suppression up to 300 GeV!


pQCD

AdS/CFTTwo extremes for Jet-Medium interactions

At the LHC, jets retain shape but significant radiation outside cone

Fragmentation functions and differential jet shapes


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


Problem: medum modification of parton shower

Recent progress: in medium splitting has probabilistic interpretation Mehtar-Tani, Salgado,Tywoniuk, 1205. 5739Casalderrey-Solana,Iancu,1105.1760Blaizot,Dominguez,Iancu,Mehtar-Tani,1209.4585

Implement in MCs: HIJING,Q-PYTHIA,Q-HERWIG,JEWELL,YaJEM

Quarkonium probes of strongly correlated QGP

(1S)

(2S)

Rapp et al., QM2012

Onium regeneration models give good description of LHC data

Important ingredient: Im V(r) -- recent progress in NRQCD models -- AdS & Latt.models show similar trends

See, for eg., T. Hatsuda, QM12 plenary

Topology of excited vacuum: Chiral Magnetic Effect

Sphaleron transitions in external B field can lead to induced charge separation – Chiral Magnetic Effect

N

C

S

=

-2

-

1

0

1

2

Kharzeev,McLerran,Warringa, NPA (2008)

outin

RP

BaaBvv

,1,1

)cos(

Conventional explanations (charge conservation + v2) exist…Pratt,Schlichting

Topology of excited vacuum: Chiral Magnetic Effect

N

C

S

=

-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 decayShuryakRV

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 PointAlso 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 ?




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 !!

Documents

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