Related papers: Pion polarizabilities: Theory vs Experiment
Recent attempts to determine the pion polarizability by dispersion relations yield values that disagree with the predictions of chiral perturbation theory. These dispersion relations are based on specific forms for the absorptive part of…
The electric alpha and magnetic beta pion Compton polarizabilities characterize the pion's deformation in the electromagnetic field of the gamma during gamma-pi Compton scattering. The pion polarizabilities are key observables, and provide…
The COMPASS collaboration at CERN has investigated pion Compton scattering, $\pi^-\gamma\rightarrow \pi^-\gamma$, at centre-of-mass energy below 3.5 pion masses. The process is embedded in the reaction…
Using the fact that the contribution of the states with isospin I=0 in the difference of the amplitudes of the processes \gamma \gamma->\pi^+\pi^- and \gamma\gamma->\pi^0\pi^0 is very small, we have analyzed the dispersion sum rules for the…
We carry out the semi--model analysis of existing data on the angular distributions of the $\gamma\gamma\rightarrow\pi^+ \pi^- ,\ \pi^0 \pi^0$ reactions with purpose to obtain S-wave cross section and D-wave's parameters. In the first time…
We study in various chiral models the pion charge radius, $\pi_{e3}$ form factor ratio, $\pi^\circ \to \gamma \gamma$ amplitude, charge pion polarizabilities, $\gamma\gamma \to \pi^\circ \pi^\circ$ amplitude at low energies and the $\pi\pi$…
An experiment on the radiative pi^+ meson photoproduction from the proton (gamma p->gamma pi^+ n) was carried out at the Mainz Microtron MAMI in the kinematic region 537 MeV <E_{gamma}<817 MeV, 140^o<theta_{gamma-gamma'}^cm<180^o. The pi^+…
We present the results for the pion electromagnetic quadrupole polarizabilities, calculated within the Nambu--Jona-Lasinio model. We obtain the sign and magnitude in agreement with the respective experimental analysis based on the…
The cross section for $\gamma\gamma\to\pi^0\pi^0$ and the pion polarizabilities are computed, within generalized chiral perturbation theory, in the full one loop approximation, {\it i.e.} up to and including order $O({p^5})$. The result…
CERN COMPASS plans measurements of gamma-pi and gamma-K interactions using 50-280 GeV pion (kaon) beams and a virtual photon target. Pion (kaon) polarizabilities and radiative transitions will be measured via Primakoff effect reactions such…
Chiral perturbation theory is the effective field theory of the strong interactions at low energies. We will give a short introduction to chiral perturbation theory for mesons and will discuss, as an example, the electromagnetic…
The electric ($\alpha_\pi$) and magnetic ($\beta_\pi$) Compton polarizabilities of both the charged and the neutral pion are of fundamental interest in the low-energy sector of quantum chromodynamics (QCD). Pion polarizabilities affect the…
We update the predictions of the SU(2) baryon chiral perturbation theory for the dipole polarisabilities of the proton, $\{\alpha_{E1},\,\beta_{M1}\}_p=\{11.2(0.7),\,3.9(0.7)\}\times10^{-4}$fm$^3$, and obtain the corresponding predictions…
The electromagnetic dipole and quadrupole polarizabilities of the neutral and charged pions are calculated in the Nambu--Jona-Lasinio model. Our results agree with the recent experimental analysis of these quantities based on Dispersion Sum…
Fermilab E781 plans measurements of gamma-Sigma and $\gamma$-pion interactions using a 600 GeV beam of Sigmas and pions, and a virtual photon target. Pion polarizabilities and radiative transitions will be measured in this experiment. The…
We compute the charged pion loop contribution to the muon anomalous magnetic moment $a_\mu$, taking into account the effect of the charged pion polarizability, $(\alpha_1-\beta_1)_{\pi^+}$. We evaluate this contribution using two different…
We reply to the Comment by Fil'kov and Kashevarov, arXiv:0805.4486 [hep-ph]. We show that the discrepancies between ChPT and dispersion theory, reported for the polarizability of the pion, result from applying dispersion theory to…
Electromagnetic polarizabilities are important parameters for understanding the interaction between photons and hadrons. For pions these quantities are poorly constrained experimentally since they can only be measured indirectly. New…
The status of the experimental and theoretical investigations on the polarizabilities of the nucleon is presented. This includes a confirmation of the validity of the previously introduced recommended values of the polarizabilities [1,2].…
A brief discussion of the elastic pion-pion scattering amplitude to two loops in chiral perturbation theory is given. Some technical details of the evaluation of two-loop diagrams are addressed, and results relevant for the pionium decay…