Journal
PHYSICAL REVIEW D
Volume 97, Issue 3, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevD.97.034506
Keywords
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Funding
- European Regional Development Fund
- Republic of Cyprus through the Research Promotion Foundation [Cy-Tera YPiODeltaOMH/SigmaTPATH/0308/31, cypro914]
- Helmholtz International Center for FAIR
- Emmy Noether Programme of the DFG (German Research Foundation) [WA 3000/1-1]
- State Ministry of Higher Education, Research and the Arts
- Theoretical Physics Department at CERN
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We investigate the quark content of the low-lying states in the I(J(P)) = 1(0(+)) sector, which are the quantum numbers of the a(0)(980) meson, using lattice QCD. To this end, we consider correlation functions of six different two-and four-quark interpolating fields. We evaluate all diagrams, including diagrams, where quarks propagate within a time slice, e.g. with closed quark loops. We demonstrate that diagrams containing such closed quark loops have a drastic effect on the final results and, thus, may not be neglected. Our analysis, which is carried out at unphysically heavy u and d quark mass corresponding to m(pi) = 296(3) MeV and in a single spatial volume of extent 2.9 fm, shows that in addition to the expected spectrum of two-meson scattering states there is an additional energy level around the two-particle thresholds of K + (K) over bar and eta + pi. This additional state, which is a candidate for the a(0)(980) meson, couples to a quark-antiquark as well as to a diquark-antidiquark interpolating field, indicating that it is a superposition of an ordinary (q) over barq and a tetraquark structure. The analysis is performed using AMIAS, a novel statistical method based on the sampling of all possible spectral decompositions of the considered correlation functions, as well as solving standard generalized eigenvalue problems.
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