We calculate the in-medium D meson self-energies in a hot pion gas induced by resonance interactions with pions. The appropriate resonances in the s, p and d waves of the D meson-pion pair are represented by low lying scalar, vector and tensor D∗ mesons. At temperatures around 200 MeV the D-meson mass drops by 30 MeV and the scattering width grows up to 60 MeV. Similar medium effects are found ...

A general expression resembling Breit-Wigner formulae is derived for the description of resonances which appear in meson-meson scattering. Starting point is a unitarised meson model, but reduced to a simpler form and freed from the specific assumption about the confining force. The parameters of the resulting “Resonance-Spectrum Expansion” are directly related to the confinement spectrum and th...

Proton Compton scattering and photoproduction of vector mesons at high energies are studied in terms of the quark model. It is shown that under the vector meson dominance hypothesis the quark model gives the rP total hadronic cross section in good agreement with the experimental data. The real-to-imaginary ratio of forward proton Compton scattering is related to the total cross sections and the...

A bstract We present positivity bounds, derived from the principles of analyticity, unitarity and crossing symmetry, that constrain low-energy constants chiral perturbation theory. Bounds are produced for 2, 3 or more flavours in meson-meson scattering with equal meson masses, up to including next-to-next-to-leading order (NNLO), using second higher derivatives amplitude. enhance bounds by most...

An exciting aspect of hadron physics is the question how a hadron changes its properties once it is put in a strongly interacting environment. Here, the vector mesons deserve special attention as they couple directly to (virtual) photons. The latter can decay into dileptons which leave the strongly interacting system untouched. Via that process information about possible in-medium modifications...

We study how the scalar f0(980) and a0(980) states are produced in the two-photon collisions and radiative decays of the φ meson through unitarized Born amplitudes with the charged pion and kaon loops followed by S-wave meson-meson scattering amplitudes. We found in a previous paper that f0(980) is generated as the bound state resonance, but a0(980) as the cusp, and find here that the nature of...

The recently observed D sJ(2317) + meson is explained as a scalar cs̄ system which appears as a bound state pole, below threshold, in the DK scattering amplitude. The standard cs̄ charmed scalar Ds0 is found at about 2.9 GeV, with a width of some 150 MeV. For the scattering length of DK in S wave we predict 5± 1 GeV−1.

The strange-quark vector current ρ-to-π meson transition form factor is computed at one-loop order using strange meson intermediate states. A comparison is made with a φ-meson dominance model estimate. We find that one-loop contributions are comparable in magnitude to those predicted by φ-meson dominance. It is possible that the one-loop contribution can make the matrix element as large as thos...