相关论文: Form factors and photoproduction amplitudes
We show how the gauge-invariance formulation given by Haberzettl is implemented in practice for photoproduction amplitudes at the tree level with form factors describing composite nucleons. We demonstrate that, in contrast to Ohta's…
We compare the effects of several form factor recipes in fits to pseudoscalar meson photoproduction data. The specific examples of pion and kaon photoproduction are used to illustrate how different choices can alter the results of such…
We consider the problem of determining amplitudes from observables for the case of pseudoscalar meson photoproduction. We find a number of surprisingly simple constraints which give necessary conditions for a complete set of measurements.…
We investigate the properties of the amplitude induced by the anomaly. In a relatively high energy region those amplitudes are constructed by the vector meson poles and the anomaly terms, in which the anomaly terms can be essentially…
We discuss the problem of gauge invariance of the vector meson photoproduction at small $x$ within the two-gluon exchange model. It is found that the gauge invariance is fulfilled if one includes the graphs with higher Fock states in the…
The general gauge-invariant photoproduction formalism given by Haberzettl is applied to kaon photoproduction off the nucleon at the tree level, with form factors describing composite nucleons. We demonstrate that, in contrast to Ohta's…
A fully gauge-invariant (pseudoscalar) meson photoproduction amplitude off a nucleon including the final-state interaction is derived. The approach based on a comprehensive field-theoretical formalism developed earlier by one of the authors…
Tensor meson photoproduction is described as either a direct production process or a consequence of the final state \pi\pi interactions. We calculate the mass distributions for selected partial waves and confront our predictions with the…
We give an introduction to and a short overview of light meson form factors. We first discuss the classical picture and how it then fits in with amplitudes in quantum field theory. We give a short overview of the main theoretical methods…
A new approach to identify the independent amplitudes along with their partial wave multipole expansions, for photo and electro-production is suggested,which is generally applicable to mesons with arbitrary spin-parity. These amplitudes…
The general gauge-invariant photoproduction formalism given by Haberzettl is applied to kaon photoproduction off the nucleon at the tree level, with form factors describing composite nucleons. Numerical results show that this…
The meson-photon transition form factors $\gamma\gamma^*\to P$ ($P$ stands for $\pi$, $\eta$ and $\eta'$) provide strong constraints on the distribution amplitudes of the pseudoscalar mesons. In this paper, these transition form factors are…
We present a complete set of 4-point amplitudes in the constructive Standard Model at tree level. Any 4-point amplitude can be obtained from the results presented here by a suitable choice of masses, a permutation of the particles (by…
Form factors are quantities that involve both asymptotic on-shell states and gauge invariant operators. They provide a natural bridge between on-shell amplitudes and off-shell correlation functions of operators, thus allowing us to use…
We perform a systematic study of two-meson form factors of the scalar, vector, and anti-symmetric tensor types within the framework of the $U(3)$ resonance chiral theory. The complete perturbative form factors in both the…
We scrutinize recent findings on the charged-pion elastic form factor and the form factors entering in neutral-meson-to-photons transition amplitudes within the framework of QCD sum rules.
Assuming the proton's light-cone wave function to be dominated by small parton virtualities and small intrinsic transverse momenta, we show that the electroproduction amplitudes at large momentum transfer factorize into parton-level…
A prescription is presented to construct manifestly gauge invariant tree-level scattering amplitudes with one or two off-shell initial-state gluons for processes with arbitrary particles in the final state, which allows for calculations…
The form factors for the radiative transitions between charmonium mesons are investigated. We employ an anisotropic lattice using a Wilson gauge action, and domain-wall fermion action. We extrapolate the form factors to $Q^2 = 0$,…
Confronted with some surprising claims about experimentally measured or theoretically expected dependencies on the involved momentum transfer of various form factors of pseudoscalar mesons, we reassess the present status of these quantities…