arXiv subjects

F. P. Sassen

Publications and source records attributed to F. P. Sassen.

4 recordsLinked to original sources

arXiv2005

The K^- αscattering length and the reaction dd \to αK^+ K^-

We present predictions for the the K^- αscattering length obtained within the framework of the multiple scattering approach. Evaluating the pole position of the K^- αscattering amplitude within the zero range approximation, we find a loosely bound K^- αstate with a binding energy of E_R = -2 ... -7 MeV and a width Γ_R = 11 ... 18 MeV. We propose to measure the K^- αscattering length through the final state interaction between the αand K^- meson produced in the reaction dd \to αK^+ K^-. It is found that the K^-αinvariant mass distribution from this reaction at energies near the threshold provides a new tool to determine the s-wave K^- αscattering length.

nucl-th↗

arXiv2003

Meson model for f_0(980) production in peripheral pion-nucleon reactions

The Juelich model for pion-pion-scattering, based on an effective meson-meson Lagrangian is applied to the analysis of the S-wave production amplitudes derived from the BNL E852 experiment pi^- p -> pi^0 pi^0 n for a pion momentum of 18.3 GeV. The unexpected strong dependence of the S-wave partial wave amplitude on the momentum transfer between the proton and neutron in the vicinity of the f_0(980) resonance is explained in our analysis as interference effect between the correlated and uncorrelated pi^0 pi^0 pairs.

hep-ph↗

arXiv2003

Lifetime of Kaonium

The kaon--antikaon system is studied in both the atomic and the strongly interacting sector. We discuss the influence of the structures of the $f_0(980)$ and the $a_0(980)$ mesons on the lifetime of kaonium. The strong interactions are generated by vector meson exchange within the framework of the standard $SU(3)_V\times SU(3)_A$ invariant effective Lagrangian. In the atomic sector, the energy levels and decay widths of kaonium are determined by an eigenvalue equation of the Kudryavtsev--Popov type, with the strong interaction effects entering through the complex scattering length for $K\bar K$ scattering and annihilation. The presence of two scalar mesons, $f_0(980)$ and $a_0(980)$, leads to a ground state energy for the kaonium atom that is shifted above the point Coulomb value by a few hundred eV. The effect on the lifetime for the kaonium decay into two pions is much more dramatic. This lifetime is reduced by two orders of magnitude from $0.8\times 10^{-16}$ sec for annihilation in a pure Coulomb field down to $3.1\times 10^{-18}$ sec when the strong interactions are included. The analysis of the two photon decay width of the $f_0(980)$ suggests a generalization of the molecular picture which reduces the lifetime of kaonium still further to $1.1\times 10^{-18}\textrm{sec}$.

hep-ph↗

arXiv2003

Investigation of light scalar resonances at COSY

The $a_0$(980) and $f_0$(980) resonances are two well established states in the excited meson spectrum. We review the most prominent theoretical models which try to explain the structure of these states. It is discussed whether data from COSY on $a_0$ and $f_0$ production in $pp$, $pn$, $pd$ and $dd$ collisions allow to distinguish between the different approaches. Very promising in this respect seems to be the measurement of the reaction $dd \to (\mathrm{^4He} a_0^0 \to) \mathrm{^4He} π^0η$ which violates isospin conservation and can be related to $a_0$-$f_0$ mixing.

hep-ph↗