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Background and Motivation Di-lepton spectra from HIC Sensitivity to EOS Summary and conclusion arXiv: 1009.3091. Di-lepton production in strongly coupled quark gluon plasma. Jian Deng ( 邓建 ) USTC with Qun Wang, Nu Xu , Pengfei Zhuang 2010-10-19 ATHIC2010 @CCNU. We want to know.

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di lepton production in strongly coupled quark gluon plasma

Background and Motivation

  • Di-lepton spectra fromHIC
  • Sensitivity to EOS
  • Summary and conclusion
  • arXiv:1009.3091

Di-lepton production in strongly coupled quark gluon plasma

JianDeng (邓建) USTC

with Qun Wang,Nu Xu, PengfeiZhuang

2010-10-19 ATHIC2010 @CCNU

we want to know
We want to know

Because of confinement, we saw no free quarks.

Can we observe QGP directly?

we know there is a cross-over from partonic phase to hadronic phase.

Electromagnetic signals have their advantages to probe the strongly coupled media.


Di-lepton signal in HIC

The dilepton signal is an excellent candidate of the electromagnetic probe.

some amazing results opened another window to understand strong interacting matter.

NA60 observed a significant excess of pairs above the yield expected from neutral meson decay

SPS NA60 96, 162302 (2006)

RHIC PHENIX arXiv:0711.2118

A strong broadening but essentially no shift in mass of rho meson spectrum is needed to explain this result


Effective temperature

Slope parameter T-eff (MeV)

T_eff gives the information of the random thermal motion and the collective flow of the thermal source.

The transition to a low-flow

region may signal a transition

from a hadronic source to

a partonic source

NA60, PRL100, 022302(2008)

Out work is try to understand this results and predict what we will get in higher energy collision such as RHIC.


Heavy Ion Collisions HIC


and Freeze-out

Initial high Q2


Partonic matter - QGP

- The hot-QCD

Initial conditions

Hard scattering production - QCD prediction

Interactions with medium - deconfinement/thermalization

Initial parton density

Initial condition in high-energy nuclear collisions - Color Glass Condensation

Cold-QCD-matter, small-x, high-parton density

- parton structures in nucleon / nucleus

S. Bass

By Richard. Heeks;

From: http://www.flickr.com/photos/11164709@N06/sets/72157607182199900/

ideal hydrodynamics eos
Ideal Hydrodynamics + EOS
  • Local conservation of net charge and energy-momentum
  • For perfect fluid
  • 4+1 equations, 5+1 unknown functions +EOS to complete
  • EOS is an input to define the relation between energy density, pressure and temperature.
  • describe: component, dof, interaction…
qgp eos


Equation Of State


Lattice EOS

Mix phase EOS

di lepton sources in hic
Di-lepton sources in HIC
  • Drell-Yan process at pre-equilibrium
  • Charmonium decay and open charm
  • Thermal quark anti-quark annihilation in QGP phase
  • Thermal charged pion annihilation in hadronic phase
  • Vector mesons, Dalitz decay, ……

Di-leptons are emitted inthe whole volume of the fireball, not from surface

dilepton from annihilation process
dileptonfrom annihilation process
  • Emission rate in thermal bath:

Parameter transformation

invariant mass distribution
Invariant mass distribution
  • HG EOS
  • Mix phase EOS
  • Lattice EOS
p t slope effective temperature
p_Tslope: Effective temperature
  • Two stage of evolution. Lattice
  • M<1 GeV: RHG .
  • small T large v
  • M>1 GeV: QGP.
  • large T small v
  • The decline near rho mass reveals a phase transition from partonicphase to hadronic phase.
  • Teff in the intermediate mass region shows the collectivity developed in the partonicstage.
eos dependence of slope parameter
EOS dependence of slope parameter

The magnitude of

T_efffitted at

large p_T is distinguishable for EOS with/out

partonic phase

T_eff~0.4Gev with partonic phase

T_eff~0.3Gev with hadronic phase only

Such behaviors of dileptons are expected to be measured and tested in future experiments

if emission from surface
If emission from surface

The behavior of Teff and v2 are similar to hadronic signals, no structure to manifest the phase transition

if switch off the radial flow
If switch off the radial flow

Moderate M,

sizeable collective flow is observable.

Large M,

no flow effect.

early emission

For small M, flow effect is dominant.

At small m_T, collective motion --> T_eff

At large m_T, harden the spectra from HG

summary and conclusion
Summary and Conclusion
  • Thermal dilepton production from sQGP in HIC at RHIC energy is investigated.
  • 2+1D ideal hydrodynamic model and different types of EOS are employed in our calculation.
  • Phase transition from HG to QGP leads to a rich structure for dilepton spectra.
  • Around M~1GeV, the slope parameter is found sensitive to the EOSand radial flow of the fireball.
  • Dilepton signals serve as clean probes to the hot and dense medium created in HIC.
eos dependence of v2 m
EOS dependence of v2(M)
  • HG EOS
  • Lattice EOS
  • Mix phase EOS
dilepton from phenix
Dilepton from PHENIX

Scaled by n_binary, without any medium modification;

1)suppress single lepton by melting D-mesons,

2)suppress pairs by switching off dynamics correlation