QCD in the nuclear medium and effects due to Cherenkov gluons

TL;DR

This paper develops in-medium gluodynamics equations, predicts Cherenkov gluon emission in nuclear media, and connects these phenomena to experimental data from RHIC, SPS, and cosmic rays, with implications for LHC.

Contribution

It introduces a classical solution for in-medium gluodynamics showing Cherenkov gluon emission and relates it to experimental observations, proposing a new mechanism for resonance asymmetries.

Findings

Cherenkov gluons explain double-humped jet structures at RHIC.

Nuclear permittivity values fitted from experimental data.

Predicted asymmetry in dilepton spectra near rho-meson.

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.