出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati

摘要：We study the manifestly exotic tetraquark D
s0 cus¯d¯ and the scalar tetraquark f0udu¯d¯ in
SU(3)c anisotropic quenched lattice QCD. We adopt the Oa-improved Wilson (clover) fermion
at β 575 on 12396 with renormalized anisotropy asat 4, and investigate the correlator of
the four-quark (4Q) system, cus¯d¯, with various quark masses including the idealized SU(4) f case.
For f0udu¯d¯ etc., we only consider connected diagrams at the quenched level, i.e., the tetraquark
f0udu¯d¯ is identical with D
s0 cus¯d¯ in the idealized SU(4) f case. First, for comparison, we
study the lowest qq¯ scalar meson, and find that it has a large mass of about 1.37GeV after chiral
extrapolation, which corresponds to f 01370. Second, we investigate the lowest 4Q state in the
spatial periodic boundary condition, and find that it is just a scattering state of two pseudoscalar
mesons, as is expected. Third, to extract spatially-localized 4Q resonances, we use the Hybrid
Boundary Condition (HBC) method, where anti-periodic and periodic boundary conditions are
imposed on quarks (c,u) and antiquarks (s¯,d¯), respectively. By applying the HBC on a finitevolume
lattice, the threshold of the two-meson scattering state is raised up, while the mass of a
compact 4Q resonance is almost unchanged. In HBC, we find a nontrivial 4Q resonance state
about 100 MeV below the two-meson threshold in some quark-mass region. Its chiral behavior
largely differs from a two-meson scattering state. The scalar tetraquark f0udu¯d¯ is found to have
the mass of about 1.1GeV after chiral extrapolation, and seems to correspond to f 0980. Then,
the manifestly exotic tetraquark D
s0 cus¯d¯ would exist around 1GeV in the idealized SU(4) f
chiral limit. Finally, MEM analysis is applied to obtain the spectral function of the 4Q system.