Microscopic study of the string breaking in QCD

TL;DR

This paper investigates the microscopic mechanisms of string breaking in QCD, showing that detailed decay vertices suppress virtual decay effects and alter decay matrix elements, impacting meson mass shifts and channel couplings.

Contribution

It introduces a microscopic decay vertex model in QCD that reduces virtual decay contributions and modifies decay matrix elements compared to phenomenological models.

Findings

String width coefficient suppresses virtual decay contributions.

Decay matrix elements differ significantly from constant gamma models.

Flattening potential can mimic decay channel effects.

Abstract

Theory of strong decays defines in addition to decay widths, also the channel coupling and the mass shifts of the levels above the decay thresholds. In the standard decay models of the 3P0 type the decay vertex is taken to be a phenomenological constant "gamma" and such a choice leads to large mass shifts of all meson levels due to real and virtual decays, the latter giving a divergent contribution. Here we show that taking the microscopic details of decay vertex into account, one obtains new string width coefficient, which strongly suppresses virtual decay contribution. In addition for a realistic space structure of the decay vertex of highly excited states, the decay matrix elements appear to be strongly different from those, where the constant "gamma" is used. From our analysis also follows that so-called flattening potential can imitate the effects of intermediate decay channels.