@ brookhaven national laboratory april 2008 spectral functions of one, two, and three quark...
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@ Brookhaven National Laboratory@ Brookhaven National LaboratoryApril 2008April 2008
Spectral Functions of
One, Two, and Three Quark Operators
in the Quark-Gluon Plasma
Spectral Functions of
One, Two, and Three Quark Operators
in the Quark-Gluon Plasma
Masayuki ASAKAWAMasayuki ASAKAWA
Department of Physics, Osaka UniversityDepartment of Physics, Osaka University
M. Asakawa (Osaka University)
QCD Phase Diagram
CSC (color superconductivity)
QGPQGP ((quark-gluon plasmaquark-gluon plasma))
Hadron Phase
T
B
• chiral symmetry breaking• confinement
order ?
1st order
crossover
CEP(critical end point)160-190 MeV
5-100
100MeV ~ 1012 K
RHIC
LHC
M. Asakawa (Osaka University)
Microscopic Understanding of QGP
In condensed matter physics, common to start from one particle states, then proceed to two, three, ... particle states (correlations)
Importance of Microscopic Properties of matter,in addition to Bulk Properties
Spectral Functions:
One Quark
Two Quarks
mesons
color singlet
• octet
diquarks
Three Quarks
baryons
......
need to fix gauge
need to fix gauge
need to fix gauge
Kitazawa’s talk
M. Asakawa (Osaka University)
Spectral Function Definition of Spectral Function (SPF)
0( ) /
0 / 43
,
( , )0 0 (1 ) ( )
(2 )
( )
0 :
n n
mn
E N TP T
mnn m
k k en J m m J n e k P
Z
J
: Boson(Fermion)
A Heisenberg Operator with some qua
n
mn m n
n P
P P P
ntum #
: Eigenstate with 4-momentum
• SPF is peaked at particle mass and takes a broad form for a resonance
Information on• Dilepton production• Photon Production• J/ suppression...etc. : encoded in SPF
M. Asakawa (Osaka University)
Photon and Dilepton production rates
Dilepton production rate
Photon production rate
3
3
( , )
exp( ) 1Td R p p
d p T
4 2
4 2 2
(2 )( , )
3 exp( ) 1l l T L
d R p
d p p T
(for massless leptons)
where T and L are given by
: QCD EM current spectral function
( , ) ( , )( ) ( , )( )T T L Lp p P p P
2 1 1
3 3 3emJ j u u d d s s
0 0 0( , ) ( , ) ( , )T T L Lk k k k P k k P
M. Asakawa (Osaka University)
Lattice calculation of spectral functions
3
3
( , )
exp( ) 1Td R p p
d p T
No calculation yet for finite momentum light quark spectral functions
LQGP collaboration, in progress
Calculation for zero momentum light quark spectral functions by two groups
4 2
4 2 2
(2 )( , )
3 exp( ) 1l l T L
d R p
d p p T
T = L @ zero momentum
Since the spectral function is a real time quantity, necessary to use MEM (Maximum Entropy Method)
So far, only pQCD spectral function has been usedSo far, only pQCD spectral function has been used
M. Asakawa (Osaka University)
QGP is strongly coupled, but...
D’Enterria, LHC workshop @CERN 2007
M. Asakawa (Osaka University)
Lattice calculation of spectral functions
3
3
( , )
exp( ) 1Td R p p
d p T
No calculation yet for finite momentum light quark spectral functions
LQGP collaboration, in progress
Calculation for zero momentum light quark spectral functions by two groups
4 2
4 2 2
(2 )( , )
3 exp( ) 1l l T L
d R p
d p p T
T = L @ zero momentum
Since the spectral function is a real time quantity, necessary to use MEM (Maximum Entropy Method)
So far, only pQCD spectral function has been usedSo far, only pQCD spectral function has been used
M. Asakawa (Osaka University)
Spectral Functions above Tc
Asakawa, Nakahara & Hatsuda [hep-lat/0208059]
m~ms
at T/Tc= 1.4ss-channel
(ω
)/ω
2
Lattice Artifact
peak structure
spe
ctra
l fu
nct
ion
s
M. Asakawa (Osaka University)
Another calculation
dile
pto
n p
rodu
ctio
n ra
te
Karsch et al., 2003
~2 GeV @1.5Tc
massless quarks
How about for heavy quarks?
smaller lattice
log scale!
In almost all dilepton calculations from QGP, pQCD expression has been used
M. Asakawa (Osaka University)
J/non-dissociation above Tc
J/ (p 0) disappearsbetween 1.62Tc and 1.70Tc
Lattice Artifact
Lattice Artifact
Asakawa and Hatsuda, PRL 2004
2( ) /
M. Asakawa (Osaka University)
Result for PS channel (c) at Finite T
c (p 0) also disappears
between 1.62Tc and 1.70Tc
A() 2()
Asakawa and Hatsuda, PRL 2004
M. Asakawa (Osaka University)
Statistical and Systematic Error Analyses in MEM
The Larger the Number of Data Pointsand the Lower the Noise Level
The closer the result isto the original image
Generally,
Need to do the following:
• Put Error Bars and Make Sure Observed Structures are Statistically Significant
• Change the Number of Data Points and Make Sure the Result does not Change
Statistical
Systematic
in any MEM analysis
M. Asakawa (Osaka University)
Statistical Significance Analysis for J/
Statistical Significance Analysis = Statistical Error Putting
T = 1.62Tc
T = 1.70Tc
Ave.
±1
Both Persistence and Disappearanceof the peak are Statistically Significant
M. Asakawa (Osaka University)
Dependence on Data Point Number
N= 46 (T = 1.62Tc)V channel (J/)
Data Point # Dependence Analysis = Systematic Error Estimate
M. Asakawa (Osaka University)
Baryon Operators Nucleon current
5 5( ) ( ) ( ) ( ) ( ) ( ) ( )N abc a b c a b cJ x s u x Cd x u x t u x C d x u x
1s t Ioffe current
Euclidean correlation function at zero momentum
3( ,0) ( , ) (0,0)
( ,0) ( , ) ( )
D d x J x J
D K d
• On the lattice, used s = 0, t = 1, u(x) = d(x) = q(x), JN(x) → J(x)
1exp
2( , )
exp exp2 2
TT
K
T T
M. Asakawa (Osaka University)
Spectral Functions for Fermionic Operators3( ,0) ( , ) (0,0)
( ,0) ( , ) ( )
D d x J x J
D K d
( ) ( ( )) : neither even nor odd
Thus, need to and can carry out MEM analysis in [-max, max]
0 0
0
( ) ( ), ( ) ( )
( ) ( ) ( ) ( ) 0
s s
s
semi-positivity
00 0
0 0
( ) ( ) ( ) : ( ), ( )
( ) ( )
s s
independent
• For Meson currents, SPF is odd
5
( )( )
In the following, we analyze
M. Asakawa (Osaka University)
Lattice Parameters
1. Lattice Sizes
323 32 (T = 2.33Tc)
40 (T = 1.87Tc)
42 (T = 1.78Tc)
44 (T = 1.70Tc)
46 (T = 1.62Tc)
54 (T = 1.38Tc)
72 (T = 1.04Tc)
80 (T = 0.93Tc)
96 (T = 0.78Tc)
2. = 7.0, 0 = 3.5
= a/a = 4.0 (anisotropic)
3. a = 9.75 10-3 fm
L = 1.25 fm
4. Standard Plaquette Action
5. Wilson Fermion
6. Heatbath : Overrelaxation= 1 : 4
1000 sweeps between measurements
7. Quenched Approximation
8. Gauge Unfixed
9. p = 0 Projection
10. Machine: CP-PACS
M. Asakawa (Osaka University)
Analysis Details Default Model
At zero momentum,
5
4
1 5( ) ( ) sgn( )
1282
Espriu, Pascual, Tarrach, 1983
Relation between lattice and continuum currents
3/ 2
3/ 4 15/ 4 1 1( , ) ( , )
2LAT CON
O
J x a a J xZ
• In the following, lattice spectral functions are presented
• 1OZ is assumed
max = 45 GeV ~ 3/a3 quarks)
M. Asakawa (Osaka University)
Just In• No statistical or systematic analysis has been carried out, yet
parity +parity -
ccc baryon
M. Asakawa (Osaka University)
ccc baryon channel
parity +parity -
ccc baryon
M. Asakawa (Osaka University)
Scattering Term Scattering term at 0p
1m
2m
NJ
0p
1 1( , )p
2 1( , )p
2 1 2 10 m m
• This term is non-vanishing only for
• For J/ (m1=m2), this condition becomes
2 10 zero mode
a.k.a. Landau damping
cf. QCD SR (Hatsuda and Lee, 1992)
M. Asakawa (Osaka University)
Scattering Term (two body case)1m
2m
NJ
0p
1 1( , )p
2 1( , )p
2 1 2 10 m m • This term is non-vanishing only for
2 1m m0
1 2,T m m
1 0p
(Boson-Fermion case, e.g. Kitazawa et al., 2008)
2 1m m
M. Asakawa (Osaka University)
Scattering Term (three body case)
2 3 1m m m 0
1 2 3, ,T m m m
1 0p
1m
2m
NJ
0p
1 1( , )p
2 2( , )p
3 3( , )p 3m
2 3 1m m m
M. Asakawa (Osaka University)
Negative parity: a possible interpretation
1m
2m
NJ
0p
1 1( , )p
2 1( , )p
0L
then: parity
0if
1 2,T m m
1 0p
anti-quark: parity -
M. Asakawa (Osaka University)
sss baryon channel
parity +parity -
M. Asakawa (Osaka University)
QCD Phase Diagram
CSC (color superconductivity)
QGPQGP ((quark-gluon plasmaquark-gluon plasma))
Hadron Phase
T
B
• chiral symmetry breaking• confinement
order ?
1st order
crossover
CEP(critical end point)160-190 MeV
5-100
100MeV ~ 1012 K
RHIC
LHC
Diquark, Quark-antiquark correlations
M. Asakawa (Osaka University)
Summary It is important to know one, two, three...quark spectral functions for the understanding of QGP
Mesons and Baryons (new!) exist well above Tc
A sharp peak with negative parity is observed in baryonic SPF above Tc
This can be due to diquark-quark scattering term and imply the existence of diquark correlation above Tc
Direct measurement of SPF of one and two quark operators with MEM is desired