2006/08/31 by R. D. Matheus, S. Narison, M. Nielsen +1 · 1 citation
Physics and Astronomy · #hep-ph #hep-ex #hep-lat #nucl-th
paper · pdf · doi:10.1103/physrevd.75.014005
published as Phys.Rev.D75:014005,2007 · 16 pages, 10 figures. Version to appear in Phys. Rev. D
arxiv created 2006/12/08 · arxiv updated 2009/12/01
We use QCD spectral sum rules to test the nature of the meson X(3872), assumed to be an exotic four-quark (ccqq) state with JPC=1++. For definiteness, we work with the current proposed recently by Maiani et al [1], at leading order in αs, consider the contributions of higher dimension condensates and keep terms which are linear in the light quark mass mq. We find MX=(3925+- 127) MeV which is compatible, within the errors, with he experimental candidate X(3872), while the SU(3) breaking-terms lead to an unusual mass-splitting MXs-MX=- (61+-30) MeV. The mass-difference between the neutral states due to isospin violation of about (2.6-3.9) MeV is much smaller than the value (8+-3) MeV proposed in [1]. For the b-quark, we predict MXb= (10144+-106) MeV for the Xb(bbq q), which is much below the BB* threshold in contrast to the BB* molecule prediction [2], and for the Xbs(bbs s), a mass-splitting M_Xsb-MXb=-(121+-182) MeV. Our analysis also indicates that the mass-splitting between the ground state and the radial excitation of about (225~250) MeV is much smaller than in the case of ordinary mesons and is (within the errors) flavour-independent. We also extract the decay constants, analogous to fπ, of such mesons, which are useful for further studies of their leptonic and hadronic decay widths. The uncertainties of our estimates are mainly due to the ones from the c and b quark masses.