Hadronic many-body theory predicts a strong broadening of the rho-meson spectral

function in hot and dense matter, leading to a melting of its resonance structure

as the pseudo-critical temperature is approached from below. Pertinent calculations

of thermal dilepton spectra in heavy-ion collisions, which additionally include

radiation from the quark-gluon plasma phase, are largely consistent with experimental

measurements which now cover a rather large range of collision energies, from SPS to

RHIC. The main part of this talk is devoted to analyzing the implications of this

scenario for the long-standing question of chiral symmetry restoration. Toward this

end, a combination of QCD and chiral Weinberg sum rules is utilized with inputs from

lattice-QCD for in-medium condensates and order parameters. Rather stringent

constraints on the a1(1260) spectral function - the chiral partner of the rho - are

deduced. Solutions are found which satisfy the temperature-dependent sum rules

accurately, thus suggesting that the rho melting scenario is compatible with chiral

restoration.

# From dileptons in heavy-ion collisions to chiral restoration at high temperature

Triangle Nuclear Theory Colloquium

Ralf Rapp (Texas A&M)

Tuesday, March 18, 2014 - 3:30pm

location:

Physics 298

contact:

Paul, Cristin

660-2491