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  • 标题:Lattice QCD Evidence for Exotic Tetraquark Resonance
  • 本地全文:下载
  • 作者:H. Suganuma ; K. Tsumura ; N. Ishii,F.,Okiharu
  • 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.
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