QCD in the nuclear medium and effects due to Cherenkov gluons

Abstract

The equations of in-medium gluodynamics are proposed. Their classical lowest order solution is explicitly shown for a color charge moving with constant speed. For nuclear permittivity larger than 1 it describes emission of Cherenkov gluons resembling results of classical electrodynamics. The values of the real and imaginary parts of the nuclear permittivity are obtained from the fits to experimental data on the double-humped structure around the away-side jet obtained at RHIC. The dispersion of the nuclear permittivity is predicted by comparing the RHIC, SPS and cosmic ray data. This is important for LHC experiments. Cherenkov gluons may be responsible for the asymmetry of dilepton mass spectra near rho-meson, observed in the SPS experiment with excess in the low-mass wing of the resonance. This feature is predicted to be common for all resonances. The "color rainbow" quantum effect might appear according to higher order terms of in-medium QCD if the nuclear permittivity depends on color.Comment: 29 p., 4 figs; for "Phys. Atom. Nucl." volume dedicated to 80th birthday of L.B. Okun; minor corrections on pp. 11 and 13 in v

Equations, chromopermittivity, and instabilities of the quark-gluon medium

“…Thus the terms with explicitly shown g in Eqs (10), (11) are of the order g 3 . The higher order corrections may be calculated (preliminary results are published in [5]) but we postpone their consideration for further publications. An impact of internal currents is phenomenologically taken into account by the chromopermittivity ǫ.…”

“…Surely, taking into account the hadronic channels of photon interactions at high energies one would come to the similar conclusions and the formula (17) will change 5. This contradicts to the requirement for Reǫ to be the even function of ω but can be considered as a purely phenomenological fit in some restricted region of ω.…”