文章基本信息

标题：Lattice QCD Evidence for Exotic Tetraquark Resonance
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作者：H. Suganuma ; K. Tsumura ; N. Ishii,F.,Okiharu 等
期刊名称：PoS - Proceedings of Science
印刷版ISSN：1824-8039
出版年度：2005
卷号：2005
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 f0􀀀udu¯d¯ in SU(3)c anisotropic quenched lattice QCD. We adopt the O􀀀a-improved Wilson (clover) fermion at β 5􀀀75 on 123􀀀96 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 f0􀀀udu¯d¯ etc., we only consider connected diagrams at the quenched level, i.e., the tetraquark f0􀀀udu¯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 0􀀀1370. 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 f0􀀀udu¯d¯ is found to have the mass of about 1.1GeV after chiral extrapolation, and seems to correspond to f 0􀀀980. 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.