The Y(2175) State in the QCD Sum Rule

TL;DR

This paper investigates the mass of the Y(2175) state using QCD sum rules, constructing different currents and finding results consistent with experimental observations, supporting its interpretation as a tetraquark.

Contribution

The study constructs and compares diquark-antidiquark and meson-meson currents in QCD sum rules, providing mass estimates for Y(2175) and analyzing its possible tetraquark nature.

Findings

Mass around 2.3±0.4 GeV consistent with observed Y(2175)

Small coupling to lower states like φ(1020)

Supports tetraquark interpretation of Y(2175)

Abstract

We study the mass of the state Y(2175) of J^{PC} = 1^{--} in the QCD sum rule. We construct both the diquark-antidiquark currents (ss)(s_bar s_bar) and the meson-meson currents (s_bar s)(s_bar s). We find that there are two independent currents for both cases, and derive the relations between them. The OPE convergence of these two currents is sufficiently fast, which enables us to perform good sum rule analysis. Both the SVZ sum rule and the finite energy sum rule lead to a mass around 2.3+-0.4 GeV, which is consistent with the observed mass within the uncertainties of the present QCD sum rule. The coupling of the four-quark currents to lower lying states such as \phi(1020) turns out to be rather small. We also discuss possible decay properties of Y(2175) if it is a tetraquark state.