@ brookhaven national laboratory april 2008 spectral functions of one, two, and three quark...

@ 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