ultrarelativistic heavyion collisions O bservables at RHIC and LHC elliptic flow jets heavy quarks D ynamical description micro or transport dynamics T ransport properties ID: 790074
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Slide1
Parton cascade description of ultrarelativistic heavy-ion collisions
Observables at RHIC and LHC (elliptic flow, jets, heavy quarks) Dynamical description: “micro” or transport dynamics Transport properties of the QGP IS: Gluon Thermalization with Bose-Einstein Condensation
Carsten
Greiner
IS2014, Napa Valley, December
7
th
, 2014
Slide2Heavy-ion c
ollisions are complex !No model can describe
all aspects of the QGP evolution
Glauber
Gluon
saturation
E
arly
thermalisation
D
ynamical
bulk
description
QGP
Energy
loss
jet
quenching
and
recovery
Slide3Transport dynamics via Boltzmann equation
BAMPS: Boltzmann Approach to Multi-Parton Scatterings3+1 dimensional, fully dynamic parton transport modelBoltzmann equations for on-shell partons with pQCD interactions
Z. Xu & CG, Phys. Rev. C71 (2005)Phys. Rev. C76 (2007)PYTHIA-Glauber
noneq
.
QGP
Slide4Elastic collisions
Leading-order pQCD cross sectionsDivergences screened by Debye massRunning coupling
Bethke et al. 2006
Slide5Inelastic radiative collisions
Improved Gunion-Bertsch matrix element:Fochler, Uphoff, Xu, CG Phys. Rev. D88 (2013)
Effective QCD LPM effect:Mean free pathGluon formation timeImproved Gunion Bertsch (GB) approximation
Slide6LPM cut-off
Mean free pathFormation time Independent scatterings(forbids too many interactions)Allows effectively some interference effects
No LPM effect2 → 3 process only allowed if mean free path of jet larger than formation time of radiated gluon
Slide7O. Fochler et al
,
J. Phys. G 38 (2011)
Slide8Nuclear modification factor
RAA Hadronization of high partons with AKK fragmentation functions
LPM parameter fixed by comparison to RHIC dataRealistic suppression both for RHIC and LHC Uphoff et al, arXiv:1401.1364
Slide9Heavy flavor and
charged hadron RAA at LHC
Slide10Reconstructed jets
Momentum imbalanceSenzel et al, arXiv:1309.1657
Slide11Reconstructed jets
Momentum imbalanceSenzel et al, arXiv:1309.1657
Slide12Elliptic flow v2
Same pQCD interactions lead to a sizeable elliptic flow for bulk mediumN
o hadronization for bulk medium → no hadronic after-burnerUphoff et al, arXiv:1401.1364
Slide13Shear viscosity as
QGP transport parameterReason for large elliptic flow:Small shear viscosity to entropy density ratio
From parameters to calculations:Uphoff et al, arXiv:1401.1364
Slide14Microscopic transport theory …gives QGP transport coefficients
Shear viscosity η bulk viscosity ζ heat conductivity κ - electric
conductivity σOther coefficients of interest: Heavy quark diffusion constants, susceptibilites,…
Green-Kubo relation
:
C.
Wesp
et al
Slide15… electric conductivity
Green-Kubo relation
: Lattice theory versus transport theory … and learn about the (strongly) interacting QGP Greif, Bouras, Xu, CG, PRD90 (2014) 9, 094014
Slide16In a nutshell: Gluon
Thermalization
with Bose-Einstein CondensationFrom to
New (early)
phase
:
Emergence of
Bose-Einstein
Condensation
Z.
Xu et al
,
arXiv:1410.5616
Slide17Transport Equation for BEC
Boltzmann Equation
:
gas particle
:
condensate particle
Included
Not included
Slide18For gas particles
:
Transport Equation for BEC
Slide19Transport Equation for BEC
For condensate particles
:
A small phase space volume competes a
function
.
Slide20BEC results
Onset of BEC
: without
(BUT, there are still particles
with
energy smaller than
.)
The distribution is
f
rozen out at
4
fm
/c
(onset of BEC
happens earlier)andis far from theequilibrium one.
Slide21BEC results
Onset of BEC
: without
Slide22BEC results
p
erfectagreement !Thermlization with BE Condensation
Slide23BEC results
Thermlization with BE Condensation (
) for small p
The condensation
begins at
0.376
fm
/c
.
The distribution at
small p is increasing
u
ntil
0.5
fm
/c
.
Slide24BEC results
BEC completion
at The larger the density(larger ), the faster isthe completion of thegluon condensation,and the faster is thethermal equilibration.
Scaling behaviour
of BE condensation
Slide25BEC results
Scaling behaviour of
the time when BE condensation occurs due to numerical fluctuations
Slide26BEC results
Scaling behaviour of
effective temperature
Slide27Conclusions & Outlook
Strong collective behavior of the QGP is successfully described by fluid or transport dynamicsBoth at RHIC and the LHC, hard probes (high and heavy flavor) are quenched while traversing the QGPTransport coefficients allow a connection between dynamical models and lattice QCDOnset and full process of BE condensationFuture: Improvement (and sensitivity) on LPM effectFuture: Influence
of momentum anisotropy, 2<->3 processes, quarks, and expansion on BE condensation
Slide28Thank you for your attention.
Slide29Backup slides
Slide30J.F.Gunion, G.F.Bertsch
, PRD 25, 746(1982)
T.S.Biro at el., PRC 48, 1275 (1993)S.M.Wong, NPA 607, 442 (1996)screened partonic interactions in leading order pQCD
screening mass:
LPM
suppression
:
the formation time
L
g
: mean free path
radiative part
elastic part
suppressed!
Slide31LPM - cutoff
transport model: incoherent treatment of
ggggg processesparent gluon must not scatter during formation time of emitted gluondiscard all possible interference effects (Bethe-Heitler regime)
k
t
CM frame
p
1
p
2
lab frame
k
t
t
= 1 / k
t
total boost
O. Fochler
Slide32D
meson RAA and v2 at LHCALICE data, QM12Uphoff, Fochler, Xu, CG, Phys. Lett. B 717 (2012),Uphoff, Fochler, Xu, CG, arXiv: 1408.2964
Heavy flavor and simultaneously seems difficult
Slide33Hydro vs BAMPS in 1D
x=0: Israel-Stewart
x=3: third-order rel. diss. hydro
x=5/3: approximative ‘all-orders’
>
Resummation works at strong dissipation
(large Knudsen number!).
A. El, Z. Xu, C. Greiner, PRC 81 (2010) 041901
A. Jaiswal, Phys.Rev.C87:051901,2013
Slide34bottom-up scenario of thermalization
R.Baier, A.H.Mueller, D.Schiff and D.T.Son, PLB502(2001)51 Qs-1 << t << a-3/2 Qs
-1 Hard gluons with momenta about Qs are freedand phase space occupation becomes of order 1. a-3/2 Qs-1 << t << a-5/2 Qs-1 (h+h -> h+h+s)Hard gluons still outnumber soft ones, but soft gluons give most of theDebye screening. a-5/2 Qs-1 << t << a-13/5 Qs-1 (h+h -> h+h+s; s+s -> s+s; h+s ->
sh+sh+s)Soft gluons strongly outnumber hard gluons.Hard gluons loose their entire energy to the thermal bath.
After a-13/5 Qs
-1
the system is thermalized: T ~ t
-1/3
, T
0
~
a
2/5
Q
s
Slide35Initial condition with
Color Glass Condensateh: [-0.05:0.05] and xt < 1.5 fm
Slide36A.El
, Z. Xu and CG, Nucl.Phys.A806:287,2008. ggg gg !This 3-2 is missing in the Bottom-Up scenario(Baier, Dohkshitzer, Mueller, Son (2001)).
Initial conditions: Color Glass Condensate Qs=3 GeV; coupling as=0.3pT spectraBottom up is not working as advocated: no tremendous soft gluon production,soft modes do not thermalize before the hard modes
Slide37Evolution of temperature: T
initial= 2/9 QsTemperature increases initially due to ggg->gg.Not the full Bottom-Up story...
Andrej Elas=0.3
Slide38Particle number decreases in the very first moment
No net soft gluon production at early times!Evolution of Particle Number in bottom-up scenario