Related papers: Delta --> N gamma in Large-Nc QCD
We determine the helicity amplitudes A_1/2 and radiative decay widths in the transition Lambda(1670) to gamma Y (Y=Lambda or Sigma^0). The Lambda(1670) is treated as a dynamically generated resonance in meson-baryon chiral dynamics. We…
This study examines the properties of heavy quarkonia $X$ by treating them as bound states of $Q$ and $\bar{Q}$ at the LO level within the NRQCD framework, where $Q$ represents either a charm or a bottom quark. The branching ratios for the…
According to Dijkgraaf and Vafa the effective glueball superpotential of the N=1 supersymmetric QCD coupled with an adjoint chiral multiplet is given by the planar amplitude in the 1/N expansion of a matrix model. It was shown that, when…
We present a strategy designed to separate several possible origins of the well-known enhancement of the Delta{I}=1/2 amplitude in non-leptonic kaon decays. In particular, we seek to disentangle the contribution of physics at the typical…
We examine the large-$N_c$ relations which express the electromagnetic $N$-to-$\Delta$ transition quantities in terms of the electromagnetic properties of the nucleon. These relations are based on the known large-$N_c$ relation between the…
Within fixed-t dispersion relations the results of new VPI partial-wave analysis for the multipole amplitudes $M_{1+}^{3/2},E_{1+}^{3/2}$ are successfuly described, and the resonance and nonresonance contributions into these amplitudes are…
The multipole amplitudes for the N - Delta electromagnetic transition are computed in the framework of the linear sigma model and the chiral chromodielectric model for small and moderate photon virtualities. The models include quark and…
Tetraquark properties are examined in the limit of large $N_c$ of color in QCD. The qualitative differences between molecular and compact tetraquarks are outlined. Consequences of the possible existence of compact tetraquarks are analyzed…
After presenting a survey of theoretical results concerning the structure of two-dimensional QCD, we present a numerical study related to the mass eigenstates and the decay amplitudes of higher mesonic states. We discuss in detail the fate…
We compute the one-loop QCD amplitudes for the decay of an off-shell vector boson with vector couplings into a quark-antiquark pair accompanied by two gluons keeping, for the first time, all orders in the number of colours. Together with…
The main goal of the paper is to show that we can treat the $1/N_c$ QCD corrections in the Pomeron calculus. We develop the one dimensional model which is a simplification of the QCD approach that includes $\pom \to 2 \pom$, $2 \pom \to…
We compute the leading contribution to the E2/M1 mixing ratio of the decay $\Delta\rightarrow N\gamma$ in heavy baryon chiral perturbation theory. We find the mixing ratio to be $4\% \ltap |\delta_{\rm E2/M1}| \ltap 11\%$, much larger than…
The factorization of the amplitude for the deeply virtual Compton scattering (DVCS) process gamma*(Q) gamma -> gamma gamma at high Q2 is demonstrated in two distinct kinematical domains, allowing to define the photon generalized parton…
We report results on $f_B$ and semi-leptonic $B$ decay form factors using NRQCD. We investigate $1/M$ scaling behavior of decay amplitudes. For $f_B$ Effect of higher order relativistic correction terms are also studied.
In this note, we present the result for the QCD corrections to the decay of the Higgs boson into two photons in the large-$\beta_0$ limit of QCD, providing the first two terms in the heavy-top expansion. From our results, one can easily…
We present covariant predictions of relativistic constituent quark models for pi and eta decay widths of N and Delta resonances. The results are calculated for a model decay operator within the point-form spectator approximation. It is…
We use the solutions to the recursion relations for double-off-shell fermion currents to compute helicity amplitudes for $n$-photon scattering and electron-positron annihilation to photons in the massless limit of QED. The form of these…
The D^+ --> omega + pi^+ decay is studied by decomposing its amplitude into a sum of factorizable and non-factorizable ones. Its rate is predicted as a function of mass and width of a hypothetical hybrid meson.
The nucleon-nucleon potential is analysed using the 1/N_c expansion of QCD. The NN potential is shown to have an expansion in 1/N_c^2, and the strengths of the leading order central, spin-orbit, tensor, and quadratic spin-orbit forces…
The role of the relativistic amplitudes for a number of ${\cal O}(k)$ processes usually neglected in potential model calculations of NN--bremsstrahlung is investigated. In particular, we consider the $\Delta$--excitation pole contributions…