Width of exotics from QCD sum rules : tetraquarks or molecules?

TL;DR

This paper uses QCD sum rules to analyze the widths of charmonium-like resonances, finding that a molecular interpretation aligns better with the data than tetraquark models.

Contribution

It introduces the Breit-Wigner function into QCD sum rule analysis and demonstrates that molecular models provide more stable and consistent results for resonance properties.

Findings

Sum rules with molecular components yield stable Borel curves.

Results favor molecular over tetraquark interpretations.

Widths and masses of resonances are well extracted.

Abstract

We investigate the widths of the recently observed charmonium like resonances X(3872), Z(4430) and Z_2(4250) using QCD sum rules. Extending previous analyses regarding these states as diquark-antiquark states or molecules of D mesons, we introduce the Breit-Wigner function in the pole term. We find that introducing the width increases the mass at small Borel window region. Using the OPE up to dimension eight, we find that the sum rules based on interpolating current with molecular components give a stable Borel curve from which both the masses and widths of these resonances can be well obtained. Thus the QCD sum rule approach strongly favors the molecular description of these states.