Hidden Local Field Theory and Dileptons in Relativistic Heavy Ion Collisions

Abstract

The notion of "hadronic freedom" is introduced based on the vector manifestation of hidden local symmetry and is used to suggest that the dileptons measured in relativistic heavy-ion collisions do not provide direct information on the spontaneous breaking of chiral symmetry and hence on the mechanism for mass generation of light-quark hadrons. We give arguments how the dileptons emitted from those vector mesons whose masses are shiftedà la Brown-Rho (BR) scaling by the vacuum change in temperature -as in heavy-ion collisions -and/or density -as in cold compressed matter -could be strongly suppressed in the hadronic free region between the chiral restoration point and the "flash point" at which the vector mesons recover ∼ > 90% of their free-space on-shell masses and the full strong coupling strength. It may seem ironical that the very mechanism i.e., the vector manifestation in hidden local symmetry, that is to make the mass drop and modify the spectral function is in turn responsible for the dilepton suppression. A possible falsification of this drastic prediction will be indicated. We also briefly discuss the potential role played by the holographic dimension intrinsic in gravity-gauge duality that provides a unified field theory description of hadrons -both mesons and baryons -under extreme conditions. Baryons arise as coherent states of pions and vector mesons of holographic QCD which define the ground state or the "vacuum" on which mesonic excitations could undergo BR scaling.

Conformal anomaly and the vector coupling in dense matter

“…7 The is absorbed into the HLS gauge boson through the Higgs mechanism and the gauge boson acquires its mass. F and F are the decay constants of the associated particles.…”

“…The same question was raised for high temperature, particularly, in connection with dilepton productions in heavy-ion collisions in[7].…”

Rare signals from dense baryonic matter

“…By now, there is convincing evidence that the observation of "mass shifts" might not be possible due to a too strong broadening of mesonic states in the medium. The connection of in-medium modifications to a partial restoration of the spontaneously broken symmetry is not straight forward, if not impossible [15]. Mesonic excitations in a baryon dense medium can only exist in the close vicinity of baryonic states and, as such, have to be interpreted as excitations of the baryonic virtual meson clouds.…”

Baryons and Vector Dominance in Holographic Dual QCD

“…Note that the photon-ρ coupling vanishes as g → 0, which can be interpreted as the ρ wave function vanishing at the origin when the ρ mass vanishes. 7) When one probes vector-meson properties with the dilepton as a snap-shot, one is looking at the first term of (3 . 5).…”