Mesons In QCD Sum Rules Research Articles

Strong coupling constants of charmed and bottom mesons with light vector mesons in QCD sum rules

We estimate the strong coupling constants of charmed and bottom mesons $ D_{(s)}^* $, $ D_{(s)1} $, $ B_{(s)}^* $, and $ B_{(s)1} $ with light vector mesons $ \rho $, $ \omega $, $ K^* $, and $ \phi $ within the framework of light-cone QCD sum rules. We compare our estimations to the ones predicted by other approaches.

Strong decays of heavy tensor mesons in QCD sum rules

In this paper, the tensor–vector–pseudoscalar (TVP) type of vertices are analyzed with the QCD sum rules (QCDSR) and the local-QCD sum rules (SR) in the leading-order approximation and the hadronic coupling constants [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] together with the corresponding decay widths are then calculated. The results indicate that QCDSR as well as the local-QCDSR give a consistent description. The calculated strong decay widths and decay width ratios are compared with the available experimental and other theoretical values. Finally, the total widths [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] are discussed in detail. The results show that these total widths are underestimated, especially for the tensor [Formula: see text] and [Formula: see text] mesons where the obtained predictions are almost a factor of 2 lower than measured decay widths.

Strong coupling constant of $$h_{b}$$ h b vector to the pseudoscalar and vector $$B_{c}$$ B c mesons in QCD sum rules

The strong coupling constant g$_{h_{b}B_{c}^{PS}B_{c}^{V}}$ is calculated using the three-point QCD sum rules method. We use correlation functions to obtain these strong coupling constants with contributions of both B$_{c}^{PS} $ and B$_{c}^{V}$mesons as off-shell states. The contributions of two gluon condensates as a radiative correction are considered. The results show that g$_{h_{b}B_{c}^{PS}B_{c}^{V}}=8.80\pm 2.84 GeV^{-1}$and g$_{h_{b}B_{c}^{V} B_{c}^{PS}}=9.34\pm 3.12 GeV^{-1}$ in the $B_{c}^{PS}$ and $B_{c}^{V}$ off-shell state, respectively.

Light scalar mesons in QCD sum rules with inclusion of instantons

The light scalar meson nonet above 1 GeV (i.e., the ${a}_{0}$, ${K}_{0}^{*}$ and ${f}_{0}$) are studied within the framework of QCD sum rules. In conventional QCD sum rules, the calculated masses of this nonet are degenerate, and the mass of ${K}_{0}^{*}$ is always larger than the ${a}_{0}$ in contradiction with the observed spectrum. After improving the correlation function by including instanton effects, the masses are well separated from each other. In particular, our results show glueball content plays an important role in the underlying structure of ${f}_{0}(1500)$. The sensitivity of the results on the instanton density is also discussed.

Sigma meson in QCD sum rules using a two-quark current with derivatives

We study the $\sigma$ meson in QCD sum rules using a two quark interpolating field with derivatives. In the constituent quark model, the $\sigma$ meson is composed of a quark and an antiquark in the relative p-wave state and is thus expected to have a larger overlap with an interpolating field that measures the derivative of the relative quark wave-function. While the sum rule with a current without derivatives gives a pole mass of around 1 GeV, the present sum rule with a derivative current gives a mass of around 550 MeV and a width of 400 MeV, that could be identified with the $\sigma$ meson.

Mixings of four-quark components in light nonsinglet scalar mesons in QCD sum rules

Mixings of four-quark components in the nonsinglet scalar mesons are studied in the QCD sum rules. We propose a formulation to evaluate the cross correlators of $q\overline{q}$ and $qq\overline{q}\overline{q}$ operators and to define the mixings of different Fock states in the sum rule. It is applied to the nonsinglet scalar mesons, ${a}_{0}$ and ${K}_{0}^{*}$. It is found that the four-quark operators predict lower masses than the $q\overline{q}$ operators and that the four-quark states occupy about 70%--90% of the lowest mass states.

Magnetic moment of the ρ meson in QCD sum rules

The rho-meson magnetic moment is calculated in the framework of QCD sum rules in external fields. Bare loop calculations (parton model) give 2.0. The contribution of the operators of dimension 6 reduces this value to 1.5.

Some decay modes of the1−+hybrid meson in QCD sum rules reexamined

The pionic coupling constants in the decays of the ${1}^{\ensuremath{-}+}$ hybrid meson are calculated. The double Borel transformation is invoked and the continuum contribution is subtracted. The decay widths of the processes ${1}^{\ensuremath{-}+}\ensuremath{\rightarrow}\ensuremath{\rho}\ensuremath{\pi}{,f}_{1}\ensuremath{\pi},\ensuremath{\pi}\ensuremath{\gamma}$ are around 40, 100, 0.3 MeV, respectively. A comparison is made with previous calculations using three-point correlation functions.

The Second Moment of The Structure Function for Pseudoscalar Mesons in QCD Sum Rules

The Second Moment of The Structure Function for Pseudoscalar Mesons in QCD Sum Rules

Exotic mesons in QCD sum rules

On the basis of the QCD sum rule method, a description is given of exotic mesons consisting of a light quark, antiquark, and two gluons (qqGG). The sum rules are formulated and the characteristics are computed of resonances with I=0, 1 and JPC = 1−−(0+−) quantum numbers.

Arbitrary spin meson in QCD sum rules

To analyze the meson excitations in the framework of QCD sum rules, we consider as hadron sources the nonlocal gauge-invariant quark currents and calculate the contributions of the “bare” quark loop and the 〈 G 2〉-power correction to the corresponding correlator. Our formulae describe correctly the masses of resonances on Regge trajectories α p, α ω, α A2 and α f.

Old tensor mesons in QCD sum rules

The tensor mesons f, A 2 and A 3 are analysed within the frangework of QCD sum rules. We account for the effects of gluon and quark condensates phenomenologically, via the matrix elements 〈0|g 2|0〉 and 〈0| Ψψ|0〉 . The G 2 term in the sum rules is found with the help of a new computational technique developed recently. Our results for the masses of f, A 2, A 3 and their coupling constants agree with experiment.