相关论文: Determination of Chiral Perturbarion Theory low en…
Chiral perturbation theory, the low energy effective theory of the strong interactions for the light pseudoscalar degrees of freedom, is based on effective Lagrangian techniques and is an expansion in the powers of the external momenta and…
We present a detailed analysis of S-wave Kpi scattering up to 2 GeV, making use of the resonance chiral Lagrangian predictions together with a suitable unitarisation method. Our approach incorporates known theoretical constraints at low and…
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…
A complete calculation of the corrections to pion-deuteron scattering length up to order $\chi^{3/2}$ with $\chi=m_{\pi}/M_{N}$ is performed. The calculation includes the dispersive contributions and corrections due to the explicit…
Weinberg's theorem for \pi-\pi scattering, including the Adler zero at threshold in the chiral limit, is analytically proved for microscopic quark models that preserve chiral symmetry. Implementing Ward-Takahashi identities, the isospin 0…
We set up a general framework to describe $\pi\pi$ scattering below 1 GeV based on chiral low-energy expansion with possible spin-0 and 1 resonances. Partial wave amplitudes are obtained with the $N/D$ method, which satisfy unitarity,…
We obtain reliable $\pi\pi$ scattering amplitudes consistent with experimental data, both at low and high energies, and fulfilling appropriate analyticity properties. We do this by first fitting experimental low energy ($s^{1/2}\leq1.42…
We analyze the Roy equations for the lowest partial waves of elastic pi pi scattering and demonstrate that the two S-wave scattering lengths a_0^0 and a_0^2 are the essential parameters in the low energy region: Once these are known, the…
The CP conserving amplitudes for the decays $K\to3\pi$ are calculated in Chiral Perturbation Theory at the next-to-leading order. We present the expressions in a compact form with single parameter functions only. These expressions are then…
The Khuri-Treiman formalism models the partial-wave expansion of a scattering amplitude as a sum of three individual truncated series, capturing the low-energy dynamics of the direct and cross channels. We cast this formalism into…
We review two manifestations of chiral symmetry breaking in the pion sector. First, we examine the $\pi\pi$ scattering amplitude at threshold, which is completely determined by the chiral symmetry breaking part of the strong interaction,…
It is shown that the linear correlation relates the S-wave phase shifts from the threshold up to dipion mass 900 MeV. By using this correlation at the solution of the Roy equations, the accuracy of determination of S-wave lengths is…
First it is shown that the tree amplitude for pion pion scattering in the minimal linear sigma model has an exact expression which is proportional to a geometric series in the quantity (s-$m_\pi^2$)/($m_B^2-m_\pi^2$), where $m_B$ is the…
The $\gamma\gamma \to \pi^0 \pi^0 \pi^0$ and $\gamma\gamma \to \pi^+ \pi^- \pi^0$ amplitudes are discussed in the general context of Chiral Perturbation Theory (ChPT) to $O(p^6)$. Chiral loops are found to play a major role. This makes…
We consider the $\pi\pi$ scattering amplitude obtained by Colangelo, Gasser and Leutwyler (CGL), using dispersion relations and chiral perturbation theory to two loops. We point out that the input used by CGL for energies above 1.42 GeV is…
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…
Chiral symmetry breaking may exhibit significantly different patterns in two chiral limits: N_f=2 massless flavours (m_u=m_d=0, m_s physical) and N_f=3 massless flavours (m_u=m_d=0=m_s=0). Such a difference may arise due to vacuum…
A representation of the two-loop contribution to the pion decay constant in $SU(3)$ chiral perturbation theory is presented. The result is analytic upto the contribution of the three (different) mass sunset integrals, for which an expansion…
The next-to-leading order chiral pion-nucleon Lagrangian contains seven finite low-energy constants. Two can be fixed from the nucleon anomalous magnetic moments and another one from the quark mass contribution to the neutron-proton mass…
We evaluate the amplitude for $\gamma \gamma \rightarrow \pi^0 \pi^0$ to two loops in chiral perturbation theory. The three new counterterms which enter at this order in the low-energy expansion are estimated with resonance saturation. We…