Related papers: pi-pi scattering amplitudes constrained by Roy's e…
We present an exploratory calculation of the $I=2$ $\pi-\pi$ scattering amplitude at threshold using Wilson fermions in the quenched approximation, including all the required contractions. We find good agreement with the predictions of…
Peculiarities of obtaining parameters for broad multi-channel resonances from data are discussed analyzing the experimental data on processes $\pi\pi\to\pi\pi,K\bar{K}$ in the $I^GJ^{PC}=0^+0^{++}$ channel in a model-independent approach…
The multichannel S- and P-wave amplitudes for the pion-pion scattering, constructed requiring analyticity and unitarity of the S-matrix and using the uniformization procedure, are elaborated using the dispersion relations with imposed…
Suggested by Au, Morgan, Pennington (AMP) S-wave isospin I=0 $\pi\pi$, $KK$ scattering amplitude is good enough to describe experimental data for the moment. Still it has two disadvantages for use in multiparticle partial wave analysis…
The near-threshold expansion of the $\pi \pi$ amplitude is developed using the crossing-covariant independent variables. The independent threshold parameters entering the real part of the amplitude in an explicitly Lorentz-invariant way are…
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…
We present our study of $\pi-N$ scattering in the iso-spin $I=3/2$ channel for the first time at the physical point. The calculation is performed using $N_f=2+1+1$ flavors of twisted mass fermions with clover improvement at physical pion…
The low-energy $\pi\pi$ amplitude is computed explicitly to two-loop accuracy in the chiral expansion. It depends only on six independent (combinations of) low-energy constants which are not fixed by chiral symmetry. Four of these constants…
Phase shifts for $s$-wave $\pi\pi$ scattering in both the $I=0$ and $I=2$ channels are determined from a lattice QCD calculation performed on 741 gauge configurations obeying G-parity boundary conditions with a physical pion mass and…
The CP violating parameter epsilon'/epsilon is computed using the low-energy dynamics of a chiral theory supplemented by vector resonances. The divergent contributions coming from strong pi-pi scattering are tamed by vector-meson exchange…
Starting from hyperbolic dispersion relations, we present a system of Roy--Steiner equations for pion Compton scattering that respects analyticity and unitarity requirements, gauge invariance, as well as crossing symmetry, and thus all…
The pion-pion scattering amplitudes provided by second-order chiral perturbation theory are confronted with known rigorous constraints derived from the axioms of quantum field theory. We mainly test constraints restricting the…
Pion-kaon ($\pi K$) pairs occur frequently as final states in heavy-particle decays. A consistent treatment of $\pi K$ scattering and production amplitudes over a wide energy range is therefore mandatory for multiple applications: in…
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…
A set of well known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel $S$ ($\pi\pi$, $K \bar K$, and $\eta\eta$) and $P$ ($\pi\pi$, $\rho 2\pi$, and $\rho\sigma$) wave…
The results of the recent experiments on the reaction $\pi^-p\to\pi^0\pi^0n$ performed at KEK, BNL, IHEP, and CERN are analyzed in detail. For the I=0 $\pi\pi$ S wave phase shift $\delta^0_0$ and inelasticity $\eta^0_0$ a new set of data is…
We present a preliminary analysis of $I=1$ $\pi\,\pi$ scattering at the physical point. We make use of the stochastic variant of the distillation framework (also known as sLapH) to compute the relevant two-point correlation matrices using a…
The evidences for sigma(600) and kappa(900) observed in our analyses on the pi pi and K pi scattering phase shift data are described, briefly. The analysis have been performed by the interfering amplitude method, which satisfies the…
We demonstrate that near the threshold, the pi pi scattering amplitude contains a pole with the quantum numbers of the vacuum - commonly referred to as the sigma - and determine its mass and width within small uncertainties. Our derivation…
This work presents the results of a revised analysis of the low-energy (pion laboratory kinetic energy T(sub pi) < 100 MeV) pi+ p data using recently obtained electromagnetic corrections. The measurements are analyzed assuming extended…