The quest for the holy Grail: from Glasma to Plasma Raju Venugopalan CATHIE-TECHQM workshop, Dec....
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Transcript of The quest for the holy Grail: from Glasma to Plasma Raju Venugopalan CATHIE-TECHQM workshop, Dec....
![Page 1: The quest for the holy Grail: from Glasma to Plasma Raju Venugopalan CATHIE-TECHQM workshop, Dec. 14-18, 2009 Color Glass Condensates Initial Singularity.](https://reader036.fdocuments.in/reader036/viewer/2022070411/56649f505503460f94c73856/html5/thumbnails/1.jpg)
The quest for the holy Grail: from Glasma to Plasma
Raju Venugopalan
CATHIE-TECHQM workshop, Dec. 14-18, 2009
Color Glass
Condensates
Initial
Singularity
Glasma sQGP - perfect fluid
Hadron Gas
t
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Nuclear wavefunction at high energies
At RHIC typical x ~ 0.01 . At the LHC, x ~ 5 * 10-4
PartonDensity
x= fraction of momentum of hadron carried by parton
Glue rules!
For glue, QS
2 = 1-1.4 GeV2 (RHIC)QS
2 = 2.6-4 GeV2 (LHC)
Kowalski,Lappi,RV, PRL (2008)
Nuclear wave function at high energies is a Color Glass Condensate
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CGC: effective degrees of freedom
Fields Sources
€
x 1
Time dilated, “frozen” random color charges with weight W[]
Dynamical gauge fields
Classical eqns: RG eqn. for x evolution of source dist.: resums Sln(1/x) and /kT
2 contributions in loop corrections
Saturation scale QS: Non.Pert. scale in W at x0 grows with x evol. of RG
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From CGC to Glasma
Multi-particle production from strong CGC fields:compute systematically properties of strongly correlated Glasma fields after collision
Consider T : At LO, can obtain from soln. of classical Yang-Mills eqns.
NLO terms are as large as LO for S ln(1/x) - resum to all ordersGelis,Lappi,RV (2008)
Glasma factorization => universal “density matrices W” calc. “matrix element”
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<T> in the GlasmaAt RHIC energies, in central A+A, evolution of W’s is not significant - local Gaussian dist. of sources with variance QS
2 ; at LHC, evolution is very significantKrasnitz,Nara,RV (2003)
System initially very far from equilibrium! (Tzz <0 for =0+ and ->0 for > 1/QS)
Lappi,McLerran (2006)
Initial gauge field configurations are longitudinal chromo-electric & magnetic fields localized in transverse plane
- generate Chern-Simons charges0Kharzeev,Krasnitz,RV (2002)
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Glasma flux tubes-IDumitru,Gelis,McLerran,RV (2008)
Conjecture based on pert. calculation:Glasma is a collection of “flux tubes” color screened on transverse distances ~ 1/QS
If conjecture is true, from geometry, must have
Non-perturbative (soln. of classical QCD!) computation of double inclusive gluon production in Glasma Lappi,Srednyak,RV:arXiv 0911.2068
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Glasma flux tubes-II
Three possible scales for color screening: 1/R, m (QCD), QS
For 2 =1, (0.5-2) QS2
Color screening radius ~ 0.7-1.4 QS
Quantum evolution of distributions will give additional screening
Results of non-pert. computation confirm Glasma flux tube conjecture
Flux tube size in same ball park as experiments. Some variation in value depending on observable
Iancu,Itakura,McLerran (2002)A.H.Mueller (2003)
Long range rapidity correlations -> see Dusling talkarXiv:0911.2720
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Matching Glasma dynamics to Hydro
Classical fieldClassical field / Particle Particle
f < 1
Current matching of LO Glasma YM computations to hydro - “CGC initial conditions”- assumes instantaneous thermalization
But T is far out of equilibrium in LO computations
No computations to date fully take into account NLO contributions that are as large as LO and should be resummed…
eccentricity
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Unstable quanta in the GlasmaRomatschke,RV (2006)
Boost non-invariant quantum fluctuations can grow rapidlyfor > 0
for
Strong disordering could lead to rapid isotropization, “anomalous transport”
Asakawa,Bass,Muller (2006)Dumitru,Nara,Schenke,Strikland (2008)These quantum corrections, albeit difficult to
evaluate, are no less a necessary partof early time dynamics…
3+1-D YM simulations
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Rapid isotropization in the Glasma
Resum - extend range of YM-dynamics
“Holy Grail” Spectrum of small fluctuations
Fukushima,Gelis,McLerran (2006)
Gelis,Lappi,RV (2008)
Can also compute event by event initial conditions to estimate flow fluctuations:
Similar in spirit to the event by event hydro code
NeXSPheRIO = NeXus + SPheRIO Grassi et al., arXiv:0912.0703
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Summary
The early time dynamics of HI collisions can be computed ab initio in a factorization framework
Early time Yang-Mills dynamics reveals structure of the Glasma as a collection of flux tubes color screened on distances ~ 1/QS
Quantum instabilities from the wave-function can lead to early isotropization; significant effects on final states
The factorization framework for n-point correlations is ideally suited to event-by-event analysis
Many interesting conceptual issues in understanding the Glasma -> sQGP transition