Asymmetric vector mesons produced in nuclear collisions

TL;DR

This paper explains the asymmetric shapes of vector mesons in nuclear collisions as Fano-Feshbach resonances, proposing a model involving Cherenkov gluons to account for observed deviations from traditional resonance shapes.

Contribution

It introduces a phenomenological model linking asymmetric meson mass distributions to Cherenkov gluons and Fano-Feshbach interference, providing a quantum mechanical explanation for experimental observations.

Findings

Mass distributions deviate from Breit-Wigner shape with low-mass excess.

Model parameters fit rho-meson data reasonably well.

Cherenkov gluons can explain the asymmetric resonance shapes.

Abstract

It is argued that the experimentally observed phenomenon of asymmetric shapes of vector mesons produced in nuclear media during high energy nucleus-nucleus collisions can be explained as Fano-Feshbach resonances. It has been observed that the mass distributions of lepton pairs created at meson decays decline from the traditional Breit-Wigner shape with some excess in the low-mass wing of the resonance. It is clear that the whole phenomenon is related to some interaction with the nuclear medium. Moreover, it can be further detalized in quantum mechanics as the interference of direct and continuum states in Fano-Feshbach effect. To reveal the nature of the interaction it is proposed to use a phenomenological model of the additional contribution due to Cherenkov gluons. They can be created because of the excess of the refractivity index over 1 just in the low-mass wing as required by the classical Cherenkov treatment. In quantum mechanics, this requirement is related to the positive real part of the interaction amplitude in this wing. The corresponding parameters are found from the comparison with $\rho $-meson data and admit reasonable explanation.