Eta Meson Production in Proton-Deuteron Collisions

Since many years the strong final state interaction between η-mesons and light nuclei and the discussed possibility for the formation of η-mesic nuclei has attracted broad experimental and theoretical investigations. Prominent examples are production experiments on the 3He-η final state which present an unexpected strong total cross section enhancement at threshold, indicating the presence of a pole very close to threshold. Stimulated by these results new proton-deuteron collision experiments on the η meson production have been performed in the near-threshold region and at higher excess energies using both polarized and unpolarized beams. Recent results are presented and discussed in this contribution

Eta Meson Production in Proton-Deuteron Collisions

Abstract. Since many years the strong final state interaction between η-mesons and light nuclei and the discussed possibility for the formation of η-mesic nuclei has attracted broad experimental and theoretical investigations. Prominent examples are production experiments on the 3 He-η final state which present an unexpected strong total cross section enhancement at threshold, indicating the presence of a pole very close to threshold. Stimulated by these results new proton-deuteron collision experiments on the η meson production have been performed in the near-threshold region and at higher excess energies using both polarized and unpolarized beams. Recent results are presented and discussed in this contribution

η meson physics with WASA-at-COSY

In recent years, the η meson has been a focal point of research for the WASA experiment at the Cooler Synchrotron COSY of the Research Center Jülich. Production experiments using nucleon-nucleon and nucleon-nucleus collisions have been performed, studying the η − N interaction in various configurations. A better understanding of this interaction is a key aspect in the ongoing search for η-nuclear bound states. In addition, the η meson itself represents an ideal laboratory for precision studies of the strong and electromagnetic interactions as well as for searches for beyond Standard Model physics. Large datasets were assembled using the WASA experiment to enable studies on rare and forbidden decay modes. An overview over recent highlights of the WASA η meson physics programme was given

meson physics with WASA-at-COSY

In recent years, the η meson has been a focal point of research for the WASA experiment at the Cooler Synchrotron COSY of the Research Center Jülich. Production experiments using nucleon-nucleon and nucleon-nucleus collisions have been performed, studying the η − N interaction in various configurations. A better understanding of this interaction is a key aspect in the ongoing search for η-nuclear bound states. In addition, the η meson itself represents an ideal laboratory for precision studies of the strong and electromagnetic interactions as well as for searches for beyond Standard Model physics. Large datasets were assembled using the WASA experiment to enable studies on rare and forbidden decay modes. An overview over recent highlights of the WASA η meson physics programme was given

Search for the

TheWASA-at-COSY experiment is, besides meson production processes, dedicated to studies on rare and forbidden decays of light mesons. In extensive η-production beam times, a high-statistics data set have been collected by means of proton-proton scattering which opens the door to studies on forbidden decays like the C-parity violating process η → π0e+e−. In this article, an optimized detector calibration leading to a significantly improved missing mass resolution and a preliminary decay analysis are presented

Search for the C-violating meson decay η → π0e+e− with WASA-at-COSY

TheWASA-at-COSY experiment is, besides meson production processes, dedicated to studies on rare and forbidden decays of light mesons. In extensive η-production beam times, a high-statistics data set have been collected by means of proton-proton scattering which opens the door to studies on forbidden decays like the C-parity violating process η → π0e+e−. In this article, an optimized detector calibration leading to a significantly improved missing mass resolution and a preliminary decay analysis are presented

Near threshold production of η-mesons in proton neutron collisions at ANKE

The interaction between hadrons and η-mesons is an intensively studied topic. Due to its stength it might lead to the formation of η-mesic nuclei. In order to study the characteristics of this interaction a measurement of the reaction p + d → d + η + psp has been performed at the ANKE spectrometer at the COSY accelerator of the Forschungszentrum Jülich. The two different beam momenta (p1 = 2.09 GeV/c and p2 = 2.25 GeV/c) in combination with the Fermi motion inside the target deuteron grant access to the determination of total and differential cross sections in an excess energy range from threshold up to Q = 90 MeV. While the course of the total cross section, especially near threshold, will allow to extract the scattering length adη via an s-wave final state interaction ansatz, the differential cross sections permit to verify the legitimacy of the s-wave assumption