13,076 research outputs found

    Radiative decay of the X(3872) as a mixed molecule-charmonium state in QCD Sum Rules

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    We use QCD sum rules to calculate the width of the radiative decay of the meson X(3872), assumed to be a mixture between charmonium and exotic molecular [cqˉ][qcˉ][c\bar{q}][q\bar{c}] states with JPC=1++J^{PC}=1^{++}. We find that in a small range for the values of the mixing angle, 50θ1305^0\leq\theta\leq13^0, we get the branching ratio Γ(XJ/ψγ)/Γ(XJ/ψπ+π)=0.19±0.13\Gamma(X\to J/\psi\gamma)/\Gamma(X\to J/\psi\pi^+\pi^-)=0.19\pm0.13, which is in agreement, with the experimental value. This result is compatible with the analysis of the mass and decay width of the mode J/ψ(nπ)J/\psi(n\pi) performed in the same approach.Comment: 7 pages, 9 figures; revised version accepted for publication in Phys. Rev.

    Production of the Y(4260) State in B Meson Decay

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    We calculate the branching ratio for the production of the meson Y(4260)Y(4260) in the decay BY(4260)KB^- \to Y(4260)K^-. We use QCD sum rules approach and we consider the Y(4260)Y(4260) to be a mixture between charmonium and exotic tetraquark, [cˉqˉ][qc][\bar{c}\bar{q}][qc], states with JPC=1J^{PC}=1^{--}. Using the value of the mixing angle determined previously as: θ=(53.0±0.5)\theta=(53.0\pm0.5)^\circ, we get the branching ratio B(BY(4260)K)=(1.34±0.47)×106\mathcal{B}(B\to Y(4260)K)=(1.34\pm0.47)\times10^{-6}, which allows us to estimate an interval on the branching fraction 3.0×108<BY<1.8×1063.0 \times 10^{-8} < {\mathcal B}_{_Y} < 1.8 \times 10^{-6} in agreement with the experimental upper limit reported by Babar Collaboration.Comment: 5 pages, 2 figures, 1 table. arXiv admin note: text overlap with arXiv:1105.134

    Y(4260) as a mixed charmonium-tetraquark state

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    Using the QCD sum rule approach we study the Y(4260) state assuming that it can be described by a mixed charmonium-tetraquark current with JPC=1J^{PC}=1^{--} quantum numbers. For the mixing angle around θ(53.0±0.5)0\theta \approx (53.0\pm 0.5)^{0}, we obtain a value for the mass which is in good agreement with the experimental mass of the Y(4260). However, for the decay width we find the value \Ga_Y \approx (1.0\pm 0.2) MeV which is not compatible with the experimental value \Ga \approx (88\pm 23) MeV. Therefore, we conclude that, although we can explain the mass of the Y(4260), this state cannot be described as a mixed charmonium-tetraquark state since, with this assumption, we can not explain its decay width.Comment: 9 pages, 6 figure

    The small xx behavior of the gluon structure function from total cross sections

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    Within a QCD-based eikonal model with a dynamical infrared gluon mass scale we discuss how the small xx behavior of the gluon distribution function at moderate Q2Q^{2} is directly related to the rise of total hadronic cross sections. In this model the rise of total cross sections is driven by gluon-gluon semihard scattering processes, where the behavior of the small xx gluon distribution function exhibits the power law xg(x,Q2)=h(Q2)xϵxg(x,Q^2)= h(Q^2)x^{-\epsilon}. Assuming that the Q2Q^{2} scale is proportional to the dynamical gluon mass one, we show that the values of h(Q2)h(Q^2) obtained in this model are compatible with an earlier result based on a specific nonperturbative Pomeron model. We discuss the implications of this picture for the behavior of input valence-like gluon distributions at low resolution scales.Comment: 19 pages, 3 figures; revised version; to appear in Int. J. Mod. Phys.

    A QCD sum rule calculation of the X±(5568)Bs0π±X^\pm(5568) \to B_{s}^0\pi^\pm decay width

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    To understand the nature of the X(5568)X(5568), recently observed in the mass spectrum of the Bs0π±B_{s}^0\pi^\pm system by the D0 Collaboration, we have investigated, in a previous work, a scalar tetraquark (diquak-antidiquark) structure for it, within the two-point QCD sum rules method. The result found for its mass agrees well with the experimental value. Encouraged by this finding we now extend our calculations to obtain the decay width of X(5568)X(5568) to Bs0π±B_{s}^0\pi^\pm using the three-point QCD sum rule. We obtain a value of (20.4\pm8.7)\MeV, which, on comparing with the experimental value of 21.9\pm6.4 (\mbox{sta})^{+5.0}_{-2.5}(\mbox{syst}) \MeV/c^2, reinforces the scalar four quark nature of X(5568)X(5568).Comment: Minor modifications made. Some new discussions and references adde
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