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Jozsó Zimányi (1931 – 2006)

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Jozsó ZimányiJozsó Zimányi I met Prof. Zimányi in India in 1984.I met Prof. Zimányi in India in 1984.

• Member, NA49 and PHENIX Collaborations• Nuclear Equation of State with derivative scalar

coupling.• ALCOR : A Dynamic model for hadronization.• Particle ratios in heavy ion collisions.• Charmed and strange hadron productions in heavy ion

collisions.• Exotic particles in heavy ion collisions.• Quark and hadro-chemistry.

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Photon and dilepton production Photon and dilepton production in heavy-ion collisionsin heavy-ion collisions

Bikash SinhaBikash Sinha

Saha Institute of Nuclear PhysicsSaha Institute of Nuclear Physicsandand

Variable Energy Cyclotron CentreVariable Energy Cyclotron Centre

BudapestJuly 2007

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Contemporary

Wisdom (Again?)

Lattice Calculation F.Karsch’95

No Quarks: Pure SU(N) gauge theories Phase transition Second order for N=2 1st order for N=3

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QCD nf light quarks

Phase transition 1st order nf 3

seems to be continuous for nf =2

Tc number of partonic degree of freedom in units of the string tension Tc /

Tc (nf =2) 150 MeV

Tc( nf =0) 160 MeV Glue balls

O(1GeV)

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QCD Phase Diagram

Quark Matter

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HOT DENSE HADRON MATTER

EQ of StateRadiative Properties of the

Sizzling HadronsChiral Properties

m*x

MELTING PROPERTIES ?

( Decay widths )Chiral Hadrodynamics

Mesons, Vector mesons, BaryonsNo Universal law of m*

x

Brown – RHO Scaling law does not seem to holdIe,

p

p

N

N

m

m

m

m

m

m***

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Medium effects : (Finite Temp Field th.)P. Roy, S. Sarkar, J. Alam, B.S., Nucl Physics A 653 (1999)S. Sarkar, P. Roy, J. Alam, B. S.Phys. Rev. C (1999) & Annals of Phys 2000

2/1

2

2***

1

co

o

v

v

v

v

T

T

f

f

m

m

fv Coupling between electromagnetic current & vector meson Field , ω0 Continuim ThresholdShould not

N

N

v

v

m

m

m

m **

J. AlamS. SarkarT. HatsudaT. NayakB. S. (2000)

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VARIATION OF VECTOR MESON MASS WITH TEMPERATURE

Sarkar et al. NPA 1998

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Photons

Hadronic matter Quark matter

qg->qqq->g

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B.S.PLB 1983

R / + - = const( , sq

q

Light from QGP

qq + -~ T4

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Dileptons

Hadronic matter Quark matter

e+e- qq->e+e-

e+e- qg -> q *

e+e- qq -> g *

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Space time evolution

• Relativistic hydrodynamics

∂T

Transverse expansion with boost invariance in the longitudinal direction

Equation of state : Bag model for QGP and resonance gas model for hadrons

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Isentropic expansion :

dy

dN

aRT

Aii

4)3(45

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ARri

e

r

1

),( 0

0; ),(v ri

Hydrodynamics takes care of the evolutionof the transverse motion.

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•Alam et al. PRC (2003) 054901•Data from: Aggarwal et al. (WA98 Collaboration) PRL (2000) 3595

Direct Photons at SPS

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J. Alam, S. Sarkar, T. Hatsuda, J. Phys. G (2004)

CERES

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Radiation at RHIC

J. Alam, J. Nayak, P.Roy, A. Dutt-Mazumder, B.S.: nucl-th/0508043 Jour. Phys. G (2007)

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Sometime ago it was noted that: “The ratio of the production rates (/+-) and ( o, /+-) from quark gluon plasma is independent of the space time evolution of the fireball”. Universal Signal :

Only a function of universal constants.

)( 424

TOxd

d

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)( T1nOxd

dss

(1)

(2)

ss nR 1 2

(3)

B.S.PLB 1983

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Invariant yield of thermal photons can be written as

Q QGP

M Mixed (coexisting phase of QGP and hadrons)

H Hadronic Phase

is the static rate of photon production convoluted

over the space time expansion.

xddypd

Rd

dypd

Nd

iHMQi i TT

4

,,2

2

2

2

iT dypd

Rd

2

2

0

2

2

022 *

yTyTem dypd

NddypdNdR

Thermal Photons

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Thermal photons from QGP :Thermal photons from QGP :

using hard thermal loop approximation. Again,

Resumming ladder diagrams in the effective theory

Thermal photons from hadrons :

(i) (ii) (with , , , and a1, in the intermediate state) (iii) (iv) , and &

Similarly from strange meson sector

gqq

gqgqqqqqqqqqgqgq & , ,

~s onAnnihilati &Compton

qqgqq

Collinear equation:

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Rather similar to photons, dileptons can be efficient probe for QGP – again not suffering from final state interactions.

One has to subtract out contributions from:

(a) Drell–Yan process,

(b) Decays of vector mesons within the life time of the fireball

(c) Hadronic decays occurring after the freeze out.

Invariant transverse momentum distribution of thermal dileptons (e+e- or virtual photons, *):

integrated over the invariant mass region:

xddMdydMpd

Rd

dypd

Nd

iHMQi i TT

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,,22

2

2

2 *

*

sqq 2*

GeVMm 05.12

Dileptons

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Dileptons from light vector mesons (, ) & (Hadronic Sector) :

])()(

[ 2

*

2222

2

3

2

22

2

VV

VVBE

T MmM

Mff

dypddM

Rd

)] (1 x )/)exp((1

1

8

1 s

Mwo

Consistent with e+e- V() data

fV(V) : coupling between electromagnetic current and vector meson fields

mV and V are the mass and width of the vector V and w0 are the continuum threshold above which the asymptotic freedom is restored.

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The number density as a function of temperature. Effect of mass modification and width modification is shown.

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Photons at SPS

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Photons at RHIC

J. Alam, J. Nayak, P.Roy, A. Dutt-Mazumder, B.S.: J. Phys. G 2007

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Di-electrons at RHIC

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RESULTS from the ratio:RESULTS from the ratio:

dypd

Rd

dypd

RdR

TTem 2

*2

2

2

• The variation of Rem (the ratio of the transverse momentum spectra of

photons and dileptons) has been studied for SPS, RHIC and LHC.

• Simultaneous measurements of this quantity will be very useful to

determine the value of the initial temperature of the system.

• Rem reaches a plateau beyond PT=1 GeV. The value of Rem in the

plateau region depends on Ti but largely independent of Tc, vo, Tf and the

EOS.

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2*

22

2

dypdRd

dypdRd

R TT

em

Ratio (Rem) at SPS

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2*

22

2

dypdRd

dypdRd

R TT

em

Ratio (Rem) at RHIC

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2*

22

2

dypdRd

dypdRd

R TT

em

Ratio (Rem) at LHC

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Ratio (Rem) for pQCD processes

FILTERING OUT pQCD PHOTONS

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2*

22

2

dypdRd

dypdRd

R TT

em

arXiv:0705.1591 [nucl.th]

Ratio (Rem) vs. Initial Temperature

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OBSERVATIONS:1. The medium effect on Rem is negligibly small

2. Hydrodynamic effects such as viscosity, flow get sort of erased

out by observing the ratio, Rem3. Equivalently, model dependent uncertainties also get cancelled out

through Rem4. Contributions from Quark Matter increase with the increase of the

initial temperature –

a) thermal photons mostly for hadronic phase at SPS

b) thermal photons from RHIC and more so from LHC originate

from QGP

5. Rem flattens out beyond pT ~ 0.5GeV

6. Rem increases with initial temperature and flattens out beyond T i ~

800MeV

7. In the plateau region: RemLHC > Rem

RHIC>RemLHC

8. EOS including quasi particle in the quark matter is being tackled.

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• The ratio, Rem seems to be insensitive to EOS, medium effects on hadrons, final state effects, Tc, flow. However, it is sensitive to Ti Rem can be used to estimate Ti.

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OBSERVATIONS, contd.WHY & HOW

Rem (in Born approx.) => )M(

T 4

2

2s2

S

At the end Rem still remains by far and large model independent:SPS => RHIC => LHC

Thus Rem is a universal signal of QGP,model independent and unique.

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We see that is a function of the universal constants and the temperature. Because of the slow (logarithmic) variation as with temperature, one can assume

T 2s

In an expanding system, however, Rem involves the superposition of results for all temperatures from Ti to Tf, so the effective (average) temperature, Teff will lie between Ti and Tf and T 2

effemR

This explains: SPSem

RHICem

LHCem RRR

It is also interesting to note that for s = 0.3, T=0.4GeV,(M)2 ~ 1 (Mmax=1.05, Mmin=0.28), we get: Rs~ 260.This is comparable to Rem obtained in the present calculation.

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2*

22

2

dypdRd

dypdRd

R TT

em

WHAT DO WE EXPECT at LHC

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Photons and di-electrons in the ALICE experiment

Photons

Electron-pairs

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Muon chambersPMD

Modules

PMDphotons

PMDphotons

MUON arm -pairs

MUON arm -pairs

ALICE Experiment at LHC

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/e+e- as well as

at the Large Hadron Collider

LOOKING FORWARD TO THE VERIFICATION OFTHE UNIVERSAL SIGNATURE:

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