Can the X ( 3872 ) be a 1 ++ four-quark state?

By R. Matheus, S. Narison, M. Nielsen, J. Richard. 2006

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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 J{sup PC}=1{sup ++}. For definiteness, we work with the diquark-antidiquark current proposed recently, at leading order in {alpha}{sub s}, consider the contributions of higher dimension condensates and keep terms which are linear in the light quark mass m{sub q}. We find M{sub X}=(3925{+-}127) MeV which is compatible, within the errors, with the experimental candidate X(3872), while the SU(3) breaking-terms lead to an unusual mass-splitting M{sub X{sup s}}-M{sub X}=-(61{+-}30) MeV. The mass-difference between the neutral states due to isospin violation is about (2.6{approx}3.9) MeV. For the b-quark, we predict M{sub X{sub b}}=(10144{+-}106) MeV for the X{sub b}(bbqq), which is much below the BB* threshold, and for the X{sub b}{sup s}(bbss), a mass-splitting M{sub X{sub b}{sup s}}-M{sub X{sub b}}=-(121{+-}182) MeV. Our analysis also indicates that the mass-splitting between the ground state and the radial excitation of about (225{approx}250) MeV is much smaller than in the case of ordinary mesons and is (within the errors) flavor-independent. We also extract the decay constants, analogous to f{sub {pi}}, of such mesons, which are useful for further studies of their leptonic and hadronicmore » decay widths. The uncertainties of our estimates are mainly due to the ones from the c and b quark masses.« less

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7acb123cf1e4185ba569c1ea9cb3cef3a115badc

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In Nuclear and High Energy Physics

  1. Alessandro Pilloni
  2. A. Esposito
  3. Alexander Zaitsev
  4. A. Polosa
  5. E. Klempt

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