A Hidden Local Symmetry Theory of Dileptons in Relativistic Heavy Ion Collisions

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A Hidden Local Symmetry Theory of Dileptons in
Relativistic Heavy Ion Collisions
Gerry Brown
State University of New York
G. E. Brown, M. Harada, J. W. Holt, M. Rho, C.
Sasaki http//www.arXiv.org/abs/0804.3196
4/25/08
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Brown-Rho scaling in normal nuclei
J. W. Holt et al., PRL 100 (2008) 062501
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Melting of Soft Glue and the Flash Temperature
D. Miller, Phys. Rept. 443 (2007) 55
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Mesons at and above Tc

• Degenerate SU(4) above Tc

M. Asakawa et al., NPA 715 (2003) 863c

• Massless at Tc

H.-J. Park et al., NPA 774 (2006) 889
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STAR 2004 Experiment
J. Adams et al, PRL 92 (2004) 092301
peripheral at
Assuming equilibrium at freezeout
P. Braun-Munzinger et al., nucl-th/0304013

• Standard scenario many generations

• HLS prediction one generation

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HBT

• Between Tc and Tflash hadrons propagate
  relatively freely

defined as temperature at which mesons go back
on-shell

• Stefan-Boltzmann law of radiation for massless
  bosons at Tc

?s
?s

• Energy density at Tequal

• 1 fm to equilibrate

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Hadronic Freedom
(between Tc and Tflash)
G. Brown et al, PRC 74 (2006) 024906
32 SU(4) Multiplet (massless at Tc)
?(18),a0(4),a1(27),?(3),?(2), ?f1285(12)
66 pions result at flash point
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NA60 Dileptons
Claim
Brown-Rho scaling ruled out
S. Damjanovic, NA60
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Dileptons as a probe for Brown-Rho scaling
Not a good probe
(1) Hadronic freedom mass-shifted ? mesons dont
decay until after Tflash, where most mass regained
(2) Violation of vector dominance near Tc ?
dileptons produced independent of ?
(3) Wave function suppression
(4) Phase space suppression
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Blue shifted hadrons

• ? mass shifted most

• Teff(?) ? 300 MeV

S. Damjanovic, NA60
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NA60 reconstruction of on-shell ?
Tfreezeout 110 MeV

• Most ?s seen are just the on-shell vacuum ones

S. Damjanovic, NA60
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Role of the a1

• a1 goes on-shell at Tflash

• Number of on-shell ?s doubled at flash point

• Off-shell cut down by factor ¼

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Low mass pion pairs
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Summary
(1) Violation of vector dominance ¼ suppression
(2) Kinematical factor ½ that
for off-shell ?s compared to on-shell ones
(3) Number of on-shell ?s doubled at flash point
from decay of a1

• Mass shifted off-shell ?s suppressed by a
  factor of 1/10 compared to on-shell ?s