Related papers: Master Formula Approach to $\gamma\gamma \to \pi\p…
We investigate the transition to perturbative QCD in Compton processes, by concentrating on the specific reactions $\pi \gamma \to \pi \gamma$ and pion photoproduction at moderate energy scales. New sum rules for each of the helicities…
The neutron-neutron scattering length a_nn provides a sensitive probe of charge-symmetry breaking in the strong interaction. Here we summarize our recent efforts to use chiral perturbation theory in order to systematically relate a_nn to…
We report on recent progress on the chiral unitary approach, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV and…
We compute the large $N$ effective action of the $O(N+1)/O(N)$ non-linear sigma model including the effect of the pion mass to order $m^2_{\pi}/f_{\pi}^2$. This action is more complex than the one corresponding to the chiral limit not only…
I briefly review the current status of chiral perturbation theory in the meson sector. Emphasis is given on the quest for higher precision. I discuss two examples: one where it is difficult to make a good prediction (K_L -> pi^0 gamma…
We discuss $\pi\pi$ scattering in the framework of chiral perturbation theory. In particular, we recall the predictions made some time ago for the threshold parameters and for the phase shift difference $\delta_0^0-\delta_1^1$.
We discuss chiral symmetry breaking critical points from the perspective of PCAC, correlation length scaling and the chiral equation of state. A scaling theory for the ratio $R_\pi$ of the pion to sigma masses is presented. The Goldstone…
We reexamine the $\omega \to \pi^{0} \pi^{0} \gamma $ decay, adding the effect of $\omega-\rho$ mixing to the amplitude calculated with the aid of chiral perturbation theory and vector meson dominance. We predict the neutral decay to occur…
We perform a dispersive theoretical study of the reaction \gamma\gamma\to pi^0\pi^0 emphasizing the low energy region. The large source of theoretical uncertainty to calculate the \gamma\gamma\to\pi^0\pi^0 total cross section for…
We work out predictions of the Linear Sigma Model for the $\gamma \gamma \to\pi^0 \pi^0$ cross section. We consider the sigma width, which is introduced in a consistent way with chiral Ward identities. The results of Chiral Perturbation…
The lowest-lying resonance in the QCD spectrum is the $0^{++}$ isoscalar $\sigma$ meson, also known as the $f_0(500)$. We augment SU(2) chiral perturbation theory ($\chi$PT) by including the $\sigma$ meson as an additional explicit degree…
The data on the pi- p --> M0 n, with M0 = pi0 pi0 pi0 or pi0 pi0 eta obtained in the GAMS experiment may be useful to study the sigma(400--700) and a_1^chi (1000), which can be taken as chiral partners of pi and rho, respectively. A…
We calculate two-loop massive master integrals for $e^{+}e^{-}\rightarrow2\gamma$ in terms of generalized power series with respect to electron mass. The coefficients of this series are expressed via Goncharov's polylogarithms. Our approach…
The near-threshold n p -> d pi0 cross section is calculated in chiral perturbation theory to next-to-leading order in the expansion parameter sqrt{M m_pi}/Lambda_chi. At this order irreducible pion loops contribute to the relevant…
We report on our determination of the values of the one and two loop low energy constants appearing in the Chiral Perturbation Theory calculation of the pi-pi scattering amplitude. For this we use a precise sum rule determination of…
We study the production amplitude for the reaction $NN\to NN\pi$ up to next-to-leading order in chiral perturbation theory. We show that the irreducible chiral loops at this order exactly cancel those terms that arise from the off-shell…
We calculate the $00^{++}$-wave two-meson spectra for the reactions $\gamma\gamma\to\pi^0\pi^0$, $\gamma\gamma\to\pi^+\pi^-$, $\gamma\gamma\to K^0\bar K^0$ and $\gamma\gamma\to K^+ K^-$ on the basis of: (i) the results of the $K$-matrix…
We make a thermal analysis of the light scalar susceptibilities using SU(3)-Chiral Perturbation Theory to one loop taking into account the QCD source of isospin breaking (IB), i.e corrections coming from $m_u\neq m_d$. The value of the…
We evaluate the electric and magnetic polarizabilities of charged pions in the framework of chiral perturbation theory at next-to-leading order. This requires a two-loop evaluation of the Compton amplitude near threshold. We estimate the…
After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion-pion scattering to two-loop accuracy. In…