D*Dπ andB*B

Abstract

We calculate the D * Dπ and B * Bπ couplings using QCD sum rules on the lightcone. In this approach, the large-distance dynamics is incorporated in a set of pion wave functions. We take into account two-particle and three-particle wave functions of twist 2, 3 and 4. The resulting values of the coupling constants are g D * Dπ = 12.5 ± 1 and g B * Bπ = 29 ± 3. From this we predict the partial width Γ(D * + → D 0 π + ) = 32 ± 5 keV . We also discuss the soft-pion limit of the sum rules which is equivalent to the external axial field approach employed in earlier calculations. Furthermore, using g B * Bπ and g D * Dπ the pole dominance model for the B → π and D → π semileptonic form factors is compared with the direct calculation of these form factors in the same framework of light-cone sum rules.

Strong and radiative decays of theDs0*(2317)meson in theDK-molecule picture

“…The couplings g D * Dπ and g K * Kπ are fixed by data for the strong decay widths D * → Dπ and K * → Kπ. In particular, the strong two-body decay widths Γ(D * + → D 0 π + ) and Γ(K * + → K 0 π + ) are related to g D * Dπ [64,65] and g K * Kπ as…”

New a1(1420) state: Structure, mass, and width

“…The strong couplings will be computed in the framework of the QCD light-cone sum rule (LCSR) approach [32,33], which is one of the most reliable and universal nonperturbative methods to explore hadrons' spectroscopic parameters and their decay modes. We will study the decay a 1 → f 0 ð980Þπ by treating the f 0 ð980Þ meson as the diquarkantidiquark state and evaluate the strong coupling g a 1 f 0 π in the context of the full LCSR method.…”

Spectroscopic parameters and decays of the resonance $$Z_b(10610)$$ Z b ( 10610 )

“…(28). It is well known that the soft limit considerably simplifies the QCD side of light-cone sum rule expressions [40]. At the same time, in the limit q → 0 the phenomenological side of the sum rules gains contributions which are not suppressed relative to a main term.…”

“…The mathematical methods to handle the soft-meson limit were elaborated in Refs. [40,41] and were successfully applied to tetraquark vertices in our previous articles [42][43][44][45]. In the soft limit p = p and the relevant invariant amplitudes in the correlation function depend only on one variable: p 2 .…”

“…At the same time, in the limit q → 0 the phenomenological side of the sum rules gains contributions which are not suppressed relative to a main term. [40,41]. To this end, in accordance with elaborated recipes one has to act by the operator…”