Measuring initial temperature through

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Measuring initial temperature through
Photon to dilepton ratio
VECC
Jajati K Nayak
Collaborators Jan-e Alam, Sourav Sarkar

Bikash Sinha
Variable Energy Cyclotron Centre, Kolkata, India.
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Outline of the talk
Introduction motivation
Photon and Dilepton productions
Ratio of thermal photons to dileptons
Summary and outlook
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Introduction
Feinberg,1976 McLerran Toimela,
1985 Weldon,1990 Gale Kapusta 1991
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Motivation
Focus of the present work Thermal radiation
EOS, Initial temperature (Ti), Freeze-out
condition (Tf), Nature of phase
transition, Transition temperature (TC),
Thermal yield depends on the input parameters
like
Not known unambiguously
To get rid of these uncertainties of model
parameters
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Thermal Photon and Dilepton productions
Photon productions at SPS, RHIC and LHC
Experiment measures
Hence estimation of thermal contribution is vital
Big Challenge
Again ,
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Thermal Photon productions
Invariant yield of thermal photons
1st order phase transition
Where Q,M,H are the QGP,MIX and Hadronic phase
respectively.
Static rate is convoluted over a dynamical
evolution and with an assumption of 1st order
phase transition.
Kapusta et. al,1991 Bair et. al, 1992 Aurenche
et. al,1998 Arnold et. al 2001
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Thermal Photon productions
Similarly,
H A D R MATTER O N I C
Kapusta et. al,1991 Sarkar et. al. 1992 Alam et.
al,2003,2005 Turbide et. al 2004
Neglected since contribution is less
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Hydro and initial conditions
The production rate of photons and dileptons are
evoluted through ideal and isentropic expansion.
Hydrodynamic equations are
From Isentropic expansion
The Initial energy density and velocity profiles
are given
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Thermal Photon productions
Hadron spectra
J Phys.G,34,871-882,2007
RHIC hadron spectra at c.m energy 200 GeV/A
measured by PHENIX expt.
Ti 400 MeV, Tf 120 MeV .
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Thermal Photon productions
PT spectra of photons
Photon RHIC (AuAu)
Photon SPS (PbPb)
(J. Phys. G 2007)
Phys. ReV. C,2001
With Ti400 and Tf120 MeV
With Ti200 ,Tf120 MeV
AuAu collision at c.m energy200 GeV/A
PbPb Collision at 158A GeV
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Thermal Dilepton productions
Invariant yield of thermal dileptons
Similar to photons dileptons also do not suffer
the final state interactions and retains the
maximum information of the initial state of the
hot fire ball. Measured dileptons contain the
contributions from all stages of the evolution
and from all possible interactions. For thermal
contribution
1. Drell-Yan processess. 2. Decays of the vector
mesons. 3. Hadronic decays after freezeout.
ThomaTraxler,1999 Ruskanen Altherr, 1992
Transverse momentum distribution is given as
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Thermal Dilepton productions
Dilepton production from Quark Hadronic Matter
The production of low mass dileptons in Quark
Matter phase has been calculated from photon
self energy, considered up to
QUARK MATTER
fV(V) coupling of electromagnetic current
to vector meson fields
HADRONIC MATTER
mV and GV 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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Thermal Dilepton productions
PT spectra of Dileptons
NA60 data on low mass dilepton Invariant mass
spectra of muon pairs in 158 A GeV InIn
collisions at CERN SPS experiment is explained
with this set of parameters.
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PT spectra of Dileptons
Thermal Dilepton productions
GeV
Also the same experimental data can be explained
by another set of input parameters. Hence the
model dependence of the input parameters needs
to be removed
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From hydro calculation the information we get is
tabularized
ltTgt GeV ltVfgt GeV
QGP 0.195    0.0005
MIX 0.192 0.01
HAD 0.1663  0.3656
M (GeV) 0.5 0.75 1.2
Slope-1 (GeV) 0.233 0.266 0.326
0.195
With flow developed at earlier stage (I.e, QGP)
QGP
HADRONIC
These slope-1 shows a fall like the slope-1
extracted by NA60 from the data.
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Photon and dilepton at SPS, RHIC and LHC energies
Photon pT spectra
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Photon and dilepton at SPS, RHIC and LHC energies
Photon pT spectra
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Ratio of thermal Photon to Dilepton
Studied the variation ratio Rem over pT for SPS,
RHIC and LHC energies. The ratio Rem reaches a
plateau after pT 1 GeV. Rem is of the order of
few hundred. Total Value increases if we move
from low initial temp. to high initial temp.
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Ratio of thermal Photon to Dilepton
Sensitivity of TC to the Ratio
RHIC energy density
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Ratio of thermal Photon to Dilepton
Sensitivity of EOS to the Ratio
RHIC energy density
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Ratio of thermal Photon to Dilepton
Sensitivity of Ti to the Ratio
Since it is sensitive to the initial temperature
we plot here, the Rem vs Ti for pT2 GeV.
RHIC energy density
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Sensitivity of the input parameters to individual
pT spectra and ratio, Rem
Sensitivity of TC
TC 192 MeV
TC 170 MeV
Photon less by 8.5 dilepton less by 13
Ratio, more by 5.0
Sensitivity of EOS
BAG-HRG EOS
Lattice EOS
Photon increases by 81 times Dilepton increases
by 96 times
Ratio, more by 16 only.
Sensitivity of medium effects
Mass modification and width modification
Individual spectra by 4-5 but Ratio by 1
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Summary and outlook
Explained
Dileptons SPS
In-In data.
Photons 1. WA98 PbPb data.
2. RHIC AuAu data.
Study the ratio of thermal photon to dilepton for
different energy densities with different
initial parameters and showed following the
results for RHIC experiment (c.m200 GeV/A)
But
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Summary and outlook
..It is sensitive to initial temperature Ti of
the strongly interacting System produced in the
Heavy-Ion experiment. The ratio for different Ti
is found as follows
Sensitive to Ti
So we do hope for a experimental photon to
dilepton ratio data in the coming experiments so
that some hydro initial parameters can be
constrained and the theory can be experimented.
Measure of Initial temperature
Thank you
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Back up.
The QGP phase calculation is done Resuming ladder
diagrams in the effective field theory for both
photons and dileptons.
Lagrangian for the photon emission rates in
Hadronic sector.
We have taken the following dipole form factor
for the photon production from Hadronic
channels at each vertex.
The average of the 4-momentum transfer in a
given t-channel exchange of meson X
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Dilepton from Quarkmatter
Up to order
Dilepton from hadronic vectors
Integration over mass range
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Ratio of thermal Photon to Dilepton
How the ratio is sensitive to invariant mass
range ?