Charm couplings and form factors in QCD sum rules

Abstract

We review the calculations of form factors and coupling constants in vertices with charm mesons in the framework of QCD sum rules. We first discuss the motivation for this work, describing possible applications of these form factors to heavy ion collisions and to B decays. We then present an introduction to the method of QCD sum rules and describe how to work with the three-point function. We give special attention to the procedure employed to extrapolate results obtained in the deep euclidean region to the poles of the particles, located in the time-like region. We present a table of ready-to-use parametrizations of all the form factors, which are relevant for the processes mentioned in the introduction. We discuss the uncertainties in our results. We also give the coupling constants and compare them with estimates obtained with other methods. Finally we apply our results to the calculation of the cross section of the reaction $J/\psi + \pi \rightarrow D + \bar{D^*}$.Comment: 43 pages, 26 figures, 10 table

The decay width of the $$Z_c(3900)$$Zc(3900) as an axialvector tetraquark state in solid quark–hadron duality

“…, which differ from the QCD sum rules for the three-meson hadronic coupling constants greatly [32]. It is difficult to obtain T 2 2 independent regions in the present three QCD sum rules, as no other terms to stabilize the QCD sum rules.…”

Decay widths of the spin-2 partners of the X(3872)

“…(28) is arbitrary, because the phase convention used in [51] and in this work for the heavy meson fields is different.) The g D * D * ρ coupling is set to 2.52 in [51], while it is estimated to be 4.7 ± 0.2 in [53,56] (QCDSR). On the other hand, there exist some partial cancellations in the loop integral in this case, and it turns out to be at least a factor of 5 smaller than that calculated for the pion driven contribution.…”

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