Related papers: Determination of Two-Loop $\pi\pi$ Scattering Ampl…
The phase variation of the sigma -> pi-pi amplitude is accurately determined as a function of mass from BES II data for J/Psi -> omega-pi-pi. The determination arises from interference with the strong b1(1235)-pi amplitude. The observed…
As the pion mass approaches a critical value $m_\pi^\star$ from below, an $S$-wave resonance crosses pion-baryon threshold and becomes a bound state with arbitrarily small binding energy, thus driving the scattering length to diverge. I…
Near threshold pion production experiments have been recently carried out and used to extract S--wave $\pi\pi$ scattering lengths. We emphasize here that at present these processes are related only at the tree level (and its first…
The isospin-2 pi pi system provides a useful testing ground for determining elastic hadron scattering parameters from finite-volume spectra obtained using lattice QCD computations. A reliable determination of the excited state spectrum of…
We present a determination of the pion-nucleon sigma-term based on a novel analysis of the $\pi N$ scattering amplitude in Lorentz covariant baryon chiral perturbation theory renormalized in the extended-on-mass-shell scheme. This…
I discuss the status of ongoing work to determine numerically the elastic $\pi\pi$ scattering amplitude at order $p^6$ in the framework of chiral perturbation theory.
The $\pi\pi$ interaction is studied at one loop order in the framework of Generalized Chiral Perturbation theory
We calculate the combination $2a_0^{(0)}-5a_0^{(2)}$ (the Olsson sum rule) and the scattering lengths and effective ranges $a_1$, $a_2^{(I)}$ and $b_1$, $b_2^{(I)}$ dispersively (with the Froissart--Gribov representation) using, at low…
In the context of chiral SU(2) perturbation theory, pion-kaon scattering is analysed near the threshold to fourth chiral order. The scattering amplitude is calculated both in the relativistic framework and by using an approach similar to…
I summarize the results of the complete one--loop chiral perturbation theory calculation performed recently. It is shown that it allows to accurately pin down the isospin two, S--wave $\pi \pi$ scattering length $a_0^2$. On the other hand,…
Using the method of asymptotic sum rules we estimated the size of $O(m_s p_\pi^4)$ and $O(m_s^2 p_\pi^2)$ corrections to $\pi K$ scattering amplitude in large $N_c$ limit. These corrections arise from the sixth order effective chiral…
Medium and high energy absorptive parts contribute to dispersive expressions for D- wave scattering lengths, $a^0_2$ and $a^2_2$. For the model employed by Basdevant, Frogatt and Peterson we find the D- wave driving term contributions to…
In this work we provide simple and precise parameterizations of the existing $\pi K$ scattering data from threshold up to 1.6 GeV, which are constrained to satisfy forward dispersion relations as well as three additional threshold sum…
The infrared exponentiation properties of dimensionally-regularized multi-loop scattering amplitudes are typically hidden at the level of the integrand, materializing only after integral evaluation. We address this long-standing problem by…
The $I=2$ $\pi\pi$ elastic $s$-wave scattering phase shift is measured by lattice QCD with $N_f=3$ flavors of the Asqtad-improved staggered fermions. The lattice-calculated energy-eigenvalues of $\pi\pi$ systems at one center of mass frame…
Using rapidity evolution equations we study two-to-two gauge-theory scattering amplitudes in the Regge limit. We carry out explicit computations at next-to-next-to-leading logarithmic accuracy through four loops and present new results for…
The scalar-isoscalar, scalar-isotensor and vector-isovector pi-pi amplitudes are fitted simultaneously to experimental data and to Roy's equations. The resulting amplitudes are compared with those fitted only to experimental data. No…
We construct the generating functional of two flavor chiral perturbation theory including the effects of virtual photons in the one loop approximation. As an application, we calculate the electromagnetic corrections to the elastic $\pi\pi$…
In the large $N_c$ approximation to $QCD$, the leading $\pp$ scattering amplitude is expressed as the sum of an infinite number of tree diagrams. We investigate the possibility that an adequate approximation at energies up to somewhat more…
The most general structure of an elastic partial wave amplitude when the unphysical cuts are neglected is deduced in terms of the N/D method. This result is then matched to lowest order, ${\mathcal{O}}(p^2)$, Chiral Perturbation…