On properties of the exotic hadrons from QCD sum rules

TL;DR

This paper examines how QCD sum rules can be used to determine properties of exotic hadrons like tetraquarks and pentaquarks, highlighting the importance of radiative corrections for accurate decay width calculations.

Contribution

It reveals that unlike ordinary hadrons, exotic hadrons require specific radiative corrections for proper property extraction using QCD sum rules.

Findings

Disconnected diagrams do not relate to tetraquark properties.

Radiative corrections are essential for decay width calculations.

One-loop correlation functions are insufficient for exotic hadrons.

Abstract

We discuss the specific features of extracting properties of the exotic polyquark hadrons (tetraquarks, pentaquarks) compared to the usual hadrons by the QCD sum-rule approach. In the case of the ordinary hadrons, already the one-loop leading-order correlation functions provide the bulk of the hadron observables, e.g., of the form factor; inclusion of radiative corrections modifies already nonzero one-loop contributions. In the case of an exotic hadron, the situation is qualitatively different: discussing strong decays of an exotic tetraquark meson, which provide the main contribution to its width, we show that the disconnected leading-order diagrams are not related to the tetraquark properties. For a proper description of the tetraquark decay width, it is mandatory to calculate specific radiative corrections which generate the connected diagrams.