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J. Ruppert Hot Quarks 2006, May 2006
What does the rho? Lessons from NA60's di-muon measurement.
Jörg RuppertNuclear Theory, Department of Physics,
Duke University, Durham, NC, USA
In collaboration with:
Thorsten RenkDepartment of Physics,
University of Jyväskylä, Jyväskylä, Finland
J. Ruppert Hot Quarks 2006, May 2006
Outline
1. Introduction: EM Probes of strongly interacting matter
2. Dynamical Evolution3. NA60’s 158 AGeV In-In di-muon
spectra 4. From In-In to Pb-Pb5. Conclusions
J. Ruppert Hot Quarks 2006, May 2006
EM Probes of strongly interacting matter
EM Probes of strongly interacting matter
Focus on dileptons in this talk
J. Ruppert Hot Quarks 2006, May 2006
Dilepton emission from URHICDilepton emission from URHIC
URHIC produce a hot and dense medium - but it is by all means not static!
J. Ruppert Hot Quarks 2006, May 2006
Dilepton spectra in HICsDilepton spectra in HICs
Focus on low andintermediate massregion in this talk
J. Ruppert Hot Quarks 2006, May 2006
Theory of dilepton emissionTheory of dilepton emission
(modulus factor including lepton masses)
In-medium effects and the fireball evolution as input are needed!
Averaged in-medium photon spectral function(EM correlator)
On top of that non-thermal sources (hadron decays, Drell-Yan, open charm etc.)
J. Ruppert Hot Quarks 2006, May 2006
E. M. correlator in vacuumE. M. correlator in vacuum
Continuum
V
Vector meson dominance
Rho-meson dominant!
Compilation from Rapp, Wambach,
Adv.Nucl.Phys.25:1,2000
J. Ruppert Hot Quarks 2006, May 2006
Chiral symmetry breakingChiral symmetry breaking
Chiral symmetry spontanously broken in vacuum! Chiral partners in the hadronic spectrum split. Hot and dense matter excites the vacuum:Gradual restoration of chiral symmetry => Chiral partners become degenerate!
J. Ruppert Hot Quarks 2006, May 2006
Chiral symmetry restorationChiral symmetry restoration
Barate et al, ALEPH, Eur. Phys. J. C4, 409 (1998), Compilation from Rapp, Wambach,
Adv.Nucl.Phys.25:1,2000
Vacuum
Brown, Rho, Phys. Rev.
Lett., (1991)
In-Medium rho and a1In-medium chiral mixing(leading order, M large)
Broadening e. g. from hadronic many-body calculations
Compilation from Rapp, Wambach,
Adv.Nucl.Phys.25:1,2000
Dey, Eltsky, Ioffe, Phys. Lett. B252 (1990) 620
Krippa Phys. Lett. B427 (1998) 13.
J. Ruppert Hot Quarks 2006, May 2006
SU(3) chiral model at finite densities
and temperature
SU(3) chiral model at finite densities
and temperature
J. Ruppert Hot Quarks 2006, May 2006
Hot meson gas: Pion/Rho system treated in Phi - functional
approach
Hot meson gas: Pion/Rho system treated in Phi - functional
approachPhi-Functional approach [Baym, Luttinger, Ward, Cornwall, Jackiw, Tomboulis]
Systematic resummation scheme of certain classes of diagrams:Many-Body calculation that includes non-perturbative broadening effects due toa finite width of the pion. Ruppert, Renk, Phys.Rev.C71:064903,2005
approximation Self-energies
• Included: finite broadening• Not-included: mass shifts (disregard changes in the real part of the self-energy)
J. Ruppert Hot Quarks 2006, May 2006
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Dynamical evolution model for URHIC!
Dynamical evolution model for URHIC!
Reliable dynamical evolution modelabsolutely necessary!
J. Ruppert Hot Quarks 2006, May 2006
CERES dataCERES data
Compilation of calculations for the dilepton spectrum at CERES for different models of in-medium modifications. One fireball evolution model for all spectral functions Renk,Ruppert, Phys.Rev.C71:064903,2005.
Klingl, Kaiser, Weise, Nucl.Phys.A624:527-563,1997,
Renk, Schneider, Weise, Phys.Rev. C66:014902,2002,
Renk, Mishra, Phys.Rev.C69:054905,2004
J. Ruppert Hot Quarks 2006, May 2006
Rescaling for 158 AGeV In-In collisions
Rescaling for 158 AGeV In-In collisions
Since no freeze-out analysis is available the Pb-Pb collisionmodel is rescaled!The choice of the decoupling temperature TF=130 MeV is not strongly restricted. This translates primarily into an uncertainty in the normalization of the final result.
J. Ruppert Hot Quarks 2006, May 2006
Comparison with NA60Comparison with NA60
pt>1 GeVpt<0.5 GeV
Pt integrated
J. Ruppert Hot Quarks 2006, May 2006
From In-In to Pb-Pb!From In-In to Pb-Pb!
pt<0.5 GeV
Pt integrated
pt>1 GeV
J. Ruppert Hot Quarks 2006, May 2006
What dominates M>1 GeV? QGP vs. low T
four pion annihilation?
What dominates M>1 GeV? QGP vs. low T
four pion annihilation?
van Hees, Rapp, hep-ph/0603084
Low T contributions would be significant due to fugacity !
Is such a description valid down to Tf?
Is chiral mixing effective at low T?Can low T contributions account for NA60’s pt cuts (next slide)?
?
?
J. Ruppert Hot Quarks 2006, May 2006
QGP vs. low T four pion: pt-dependence
QGP vs. low T four pion: pt-dependence
Significant QGP contribution (high T, insignificant flow)
High T => exponentialSpectrum in pt
Significant low T chiral mixing contribution (significant flow)
Flow pushes to higher pt =>exponential spectrum withshoulder in pt Different evolution models (different T, different flow) can
lead to similar spectra either at low pt or high pt at given M but not at both..
J. Ruppert Hot Quarks 2006, May 2006
Comparison I: Integrated pt Comparison I: Integrated pt
van Hees, RappRenk, Ruppert, hep-ph/0605130
J. Ruppert Hot Quarks 2006, May 2006
Comparison II: pt<0.5 GeVComparison II: pt<0.5 GeV
van Hees, RappRenk, Ruppert, hep-ph/0605130
J. Ruppert Hot Quarks 2006, May 2006
Comparison III: pt>1 GeVComparison III: pt>1 GeV
van Hees, RappRenk, Ruppert, hep-ph/0605130
J. Ruppert Hot Quarks 2006, May 2006
ConclusionsConclusions