Speaker
Gernot Eichmann
Description
I will present results for tetraquark masses in the covariant Dyson-Schwinger/Bethe-Salpeter approach. We study two setups: in the first one, the system is simplified to a coupled diquark/antidiquark-meson/meson equation. In the second case we solve a genuine four-body equation where quarks interact via gluon exchange. In both cases we find a light scalar-isoscalar state in the ~500 MeV region. The second approach is especially interesting because no meson or diquark ingredients appear in the equation. However, one can exploit the properties of the permutation group S4 to isolate the phase space domains that are influenced by pion poles in unphysical regions. If these kinematic domains are excluded by hand, the mass goes up to 1.5-2 GeV, as one might expect for a four-quark state without further non-trivial dynamics. These results suggest that the sigma/f0(500) is a four-quark bound state that is strongly dominated by pion-pion components. The masses of the remaining multiplet members, kappa and a0/f0, behave similarly.
Primary author
Co-authors
Christian Fischer
(R)
Walter Heupel
(urn:Google)
