QCD sum rule Study of the $d^*(2380)$

TL;DR

This paper uses QCD sum rules with specially constructed six-quark currents to estimate the mass of the $d^*(2380)$ dibaryon, finding results consistent with experimental observations and establishing a lower mass bound.

Contribution

It introduces a systematic construction of six-quark interpolating currents and applies QCD sum rules to analyze the $d^*(2380)$, including effects of mixing with singlet dibaryon fields.

Findings

Estimated $d^*(2380)$ mass: 2.4 ± 0.2 GeV

Lower mass bound: > 2.25 GeV

Mixing effects do not significantly alter the results

Abstract

We systematically construct $I(J^P)=0(3^+)$ six-quark local interpolating currents without derivative operators. We discuss the best choice of operator, and select three $\Delta$-$\Delta$ like operators to perform QCD sum rule analyses to calculate the mass of the $d^*(2380)$. The mass extracted from this analysis is $M_{d^*} = 2.4\pm0.2$ GeV, consistent with the $d^*(2380)$ mass observed by the WASA detector at COSY. We also obtain a sum-rule lower mass bound $M_{d^*} > 2.25$ GeV. We also consider the effect of mixing of singlet dibaryon fields with the same quantum numbers, and perform the QCD sum rule analysis of the mixed interpolating current and extract the mass of the $d^*(2380)$ and its lower mass bound. With optimized mixing parameters, we find that the mixed current does not change the numerical result significantly.