相关论文: Existence of sigma meson in pi-pi scattering
The scattering length and effective range of the piSigma channel are studied in order to characterize the strangeness S=-1 meson-baryon scattering and the Lambda(1405) resonance. We examine various off-shell dependence of the amplitude in…
With the aim of generating new constraints on the OZI suppressed couplings of chiral perturbation theory a set of six equations of the Roy and Steiner type for the $S$- and $P$-waves of the $\pi K$ scattering amplitudes is derived. The…
We show that it makes sense to coarse grain hadronic interactions such as $\pi\pi$ and $\pi N$ reactions following previous work on NN scattering. Moreover, if the interaction is taken to be given by chiral dynamics at long distances above…
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 (light but not-so-light) strange quark may play a special role in the low-energy dynamics of QCD. The presence of strange quark pairs in the sea may have a significant impact of the pattern of chiral symmetry breaking : in particular…
We study the \eta' N interaction within a chiral unitary approach which includes \pi N, \eta N and related pseudoscalar meson-baryon coupled channels. Since the SU(3) singlet does not contribute to the standard interaction and the \eta' is…
The lightest QCD resonance, the sigma, has been recently fixed in the pi-pi scattering amplitude. The nature of this state remains nowadays one of the most intriguing and difficult issues in particle physics. Its coupling to photons is…
Complex poles of the unitarized pi-pi scattering amplitude in nuclear matter are studied. Partial restoration of chiral symmetry is modeled by the decrease of in-medium pion decay constant f*_{pi}. For large chiral restoration…
It is pointed out that the hadron spectroscopy should be a study of the structure of the QCD vacuum, low-energy elementary excitations on top of which are hadrons. Concentrating on the dynamical breaking of the chiral symmetry in the QCD…
We evaluate, within one-loop chiral perturbation theory, the two-pion exchange diagrams with single and double delta-isobar excitation contributing to elastic NN-scattering. We find that virtual $\Delta$-excitation processes (in the static…
Dispersive approaches provide model independent description of meson-meson scattering. We first review here the use of dispersion relations to obtain a model independent unitarization of Chiral Perturbation Theory amplitudes, that establish…
The trace anomaly term in the low energy chiral Lagrangian is established by deriving a low energy theorem for $\gamma \gamma \rightarrow \pi^0\pi^0$ scattering. It contributes to $\sigma(\gamma \gamma \rightarrow \pi^0\pi^0)$ in the same…
On the basis of a simultaneous description of the isoscalar s-wave channel of the $\pi\pi$ scattering (from the threshold up to 1.9 GeV) and of the $\pi\pi\to K\bar{K}$ process (from the threshold to $\sim$ 1.4 GeV) in the model-independent…
The riddle of the sigma is recast in a way that tries to differentiate fact from fiction as a basis for future/further discussion. By doing this, it is hoped that the role of the sigma as dominating the ubiquitous $\pi\pi$ interactions…
In this work we construct the $\pi\pi$ scattering amplitude $T^0_0$ with regular analytical properties in the $s$ complex plane, which describes simultaneously the data on the $\pi\pi$ scattering, $\phi\to\pi^0\pi^0\gamma$ decay, and…
Broken chiral symmetry has become the basis for a unified treatment of hadronic interactions at low energies. After reviewing mechanisms for spontaneous chiral symmetry breaking, I outline the construction of the low--energy effective field…
We study the dependence on the number of colors of the leading pi pi scattering amplitude in chiral dynamics. We demonstrate the existence of a critical number of colors for and above which the low energy pi pi scattering amplitude computed…
We use a nonperturbative approach which combines coupled channel Lippmann Schwinger equations with meson-meson potentials provided by the lowest order chiral Lagrangians. By means of one parameter, a cut off in the momentum of the loop…
A theoretical study of Goldstone boson scattering based on the chiral Lagrangian with vector meson fields is presented. In application of a recently developed novel approach we extrapolate subthreshold partial-wave amplitudes into the…
Precise measurement of the $\pi\pi$-phase shift $\delta^0_0(E)$ at very low energies would provide, for the first time, the experimental evidence in favour of or against the existence of a large quark condensate in the QCD vacuum, which is…