相关论文: Dispersion relations and soft pion theorems for K …
We discuss the reactions $\pi p \to \pi p$ and $\pi p \to \pi p \gamma$ from a general quantum field theory (QFT) point of view, describing these reactions in QCD and lowest relevant order of electromagnetism. We consider the pion-proton…
We present here an extension of our model for the pion, which we used previously to calculate its diagonal structure function, to the off-forward case. The imaginary part of the off-forward gamma^* pi -> gamma^* pi scattering amplitude is…
We prove new soft pion theorem for the near threshold pion production by a hard electromagnetic probe. This theorem relates various near threshold pion production amplitudes to the nucleon distribution amplitudes. The new soft pion theorem…
Building upon our recent study arXiv:1709.04325, we investigate the feasibility of calculating the pion distribution amplitude from suitably chosen Euclidean correlation functions at large momentum. We demonstrate in this work the advantage…
We give predictions for the partial wave amplitudes of pion photoproduction near threshold by means of dispersion relations at fixed t. The free parameters of this approach are determined by a fit to experimental data in the energy range…
In the scaling regime, amplitudes for backward virtual Compton scattering and hadron annihilation into two photons depend on structure functions that describe the hadron-photon transition at the partonic level. We construct simple…
A pion distribution amplitude, derived from nonlocal QCD sum rules, has been employed to calculate $F_{\gamma^*\gamma\to\pi}(Q^2)$ using light-cone sum rules, and $F_{\pi}(Q^2)$ in NLO QCD perturbation theory. Predictions are presented for…
We investigate the photon emission in pion-pion and pion-proton scattering in the soft-photon limit where the photon energy $\omega \to 0$. The expansions of the $\pi^{-} \pi^{0} \to \pi^{-} \pi^{0} \gamma$ and the $\pi^{\pm} p \to…
The form factors of the light pseudoscalar mesons are investigated in a dispersive formalism based on hadronic unitarity, analyticity and the OPE expansion of the QCD Green functions. We propose generalizations of the original mathematical…
The pion structure function is investigated in a simple model, where the pion and its constituent quark fields are coupled through the simplest pseudoscalar coupling. The imaginary part of the forward gamma* pi -> gamma* pi scattering…
A dynamical model for S-- and P--wave correlated $2 \pi$ (and $K \bar K$) exchange between a kaon and a nucleon is presented, starting from corresponding $N \bar N \rightarrow K \bar K$ amplitudes in the pseudophysical region, which have…
We give a brief review of the theoretical description of low energy pion-pion scattering by the combined use of Chiral Perturbation Theory and Roy equations, an update of the Regge parametrization of $\pi\pi$ cross sections at high…
The implication of chiral symmetry for the pion-induced dissociation of the J/psi is examined in detail. It is shown how the low-energy dynamics of pions, constrained by chiral symmetry, affect the dissociation cross-section. The derived…
We point out that, in analogy with spin waves in antiferromagnets, all parameters describing the real-time propagation of soft pions at temperatures below the QCD chiral phase transition can be expressed in terms of static correlators. This…
We present and develop a general dispersive framework allowing us to construct representations of the amplitudes for the processes $P\pi\to\pi\pi$, $P=K,\eta$, valid at the two-loop level in the low-energy expansion. The construction…
We study the behavior of the pion dispersion relation in a pion medium at finite density and temperature. We introduce a pion chemical potential to describe the finite pion number density and argue that such description is valid during the…
An analysis of electromagnetic corrections to the (dominant) octet K -> pi pi hamiltonian using chiral perturbation theory is carried out. Relative shifts in amplitudes at the several per cent level are found.
Continuing our previous work(JHEP 0706:030,2007), large--$N_C$ techniques and partial wave dispersion relations are used to discuss $\pi\pi$ scattering amplitudes. We get a set of predictions for $O(p^6)$ low-energy chiral perturbation…
Consider the effective lagrangian for pions in the chiral limit, computed to leading order in an expansion about zero temperature. To describe the scattering of pions with small momenta, it is necessary to include not just the usual shift…
I discuss the absorption and dispersion of pions in hot matter. A two-loop calculation in the framework of chiral perturbation theory is presented and its result is compactly written in terms of the two- and three-particle forward $\pi \pi$…