Workshop on Quark-gluon Thermalization Vienna, August 10-12, 2005
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Transcript of Workshop on Quark-gluon Thermalization Vienna, August 10-12, 2005
Workshop on Quark-gluon Thermalization Vienna, August 10-12, 2005
In collaboration with Zuo-tang Liang
Xin-Nian Wang/LBNL
Thermalization and Globally Polarized QGP in Non-central Heavy-ion Collisions
Instability and Cerenkov Radiation
Phys. Rev. Lett. 94 (2005)102301
Direct Signs for Thermalization
<pT> from away jets
<pT> from medium decay
Leadinghadrons
Medium
Fuqiang Wang
Global Orbital Angular Momentum
xz
y
Low-energy nuclear collisions:
Stiff EOSP~ E
Rotationand deformed nuclei
xz
y
p
A
0-2 2-4 4
Global Orbital Angular Momentum
xz
y
xz
y
High-energy Nuclear Collisions
Nuclei Are Spherical !
3D distribution of multiplicity and
Momentum
Heinz & Kolb’04Adil & Gyulassy’5
Transverse Gradient of Shear Velocity
,P TpartdN
dx
Distribution of number of participant projectile ortarget nucleons
( , )2
( )
Ppart
Pp
Tpart
Tpartart
z
dN
dxd
ds
p x bN
N
dxdN
dxxs
dc
Collectivelongitudinalmomentumper producedparton
x
zb
Local Orbital Angular Momentum
(x-b
/2)/
RA
zz
dpp x
dx
2 zy z
dpL x p x
dx 0 0.34 GeV/fm
2 ( ) A
dp s
dx c s R
x
Quark Scattering with fixed Ly
, ( ) ( ) ( ) ( )2i iT f T
igM q u p A q u p
E
02 2
1( )T
T
A qq
2 2
2
2 2 2 2 2,
1 1( )
(2 ) 2 ( )i
TT T
d gM q C
d q q
Screened static potential model:
20 0 ( ) ( )( ) ( ) 1
2 2 ( )T T
T Tq
g q k n pI A q A k i
E E m
: final quark spin
xT
p
n
pf
2 2( ) †
, ,2 2 2
1( ) ( )
(2 ) (2 ) 2T T T
i i
i
i k q xT TT T T
T
d d q d kC e M q M k
d x
I
Quark Polarization
2 202 2 2
4 ( )T s TT T T
d d dC K x
d x d x d x
4 ( )qq
pP
E E m
Unpolarized cross section:
20 12 2 2
ˆ( )4 ( ) ( )
( )T
T s T TT T T q
d d d p x nC K x K x
d x d x d x E E m
Polarized cross section:
0 0.34 GeV/fm2 ( ) A
dp s
dx c s R
( ) 45 at RHICc s 1
0.5 GeVx
0. 3qP
Semi-central: b=RA
xT
p
n
pf
A New Picture of A+A
Spin-orbital coupling
2
nonrelativistic limit: ( , )
8
q
m p
pP
m
4 ( )qq
pP
E E m
02
1
LSq
dVE L s
dr r m
200
1,
dV pE L
r dr
0
LSq
EP
E
xT
p
n
pf
Consequences
Single-spin asymmetry:
Polarized thermal dilepton, J/Hyperons and vector mesons
Directed flow?
Enhanced /, /pratio
Constituent Quark Recombination
sP P 2
2
4 3
3 4q s s q
q s q
P P P PP
P P P
2
2
4 3
3 4s q q s
q s s
P P P PP
P P P
2
2
5
3(1 )s
ss
PP P
P
Polarization of valence quarks + relative orbital angular momentum
Polarization of constituent quarks
0
0
1/ 2
1/ 6 2
1/ 6 2
u d u d s
s s u s s s s u
u d s u d u d s
Constituent quark model:
(l=0, color anti-symmetric)
Features of Global Hyperon Polarization
• Hyperons & anti-hyperons are similarly polarized
• PH=0 in central and increases with b
• Pq 0 for pT>> p0z, PH finite for moderate pT due to hard-soft recombination
• Contribution from directed flow at large y
Other effects
1( ) (( () () ) )
2f fM u p kS q V qk u p
P>0 P<0
Hadronic scattering:
Thoughts for the Brave…
N1
N2
N2> N1
v2 in p+A collisions?
Summary
• Shear velocity gradient leads to global polarization if there is interaction across transverse direction due to thermalization
• A new picture of QGP structure in heavy-ion collisions:– Hyperon polarization, vector meson spin
alignment, contribution to v2
• Future work: – Quantitative evaluation of hadronic interaction – Spin transport: spintronics of strong interaction