Heavy Ion Theory Review Raju Venugopalan Brookhaven National Laboratory LHC week in Split, October 1-6, 2012
Dec 13, 2015
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 ?
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
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!
Jet probes of strongly correlated QGP
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
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. 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 ?
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 !!