Search for the eta-mesic Helium bound state with the WASA-at-COSY facility

TL;DR

This study searches for eta-mesic helium nuclei using the WASA-at-COSY facility, employing a ramped beam technique to analyze specific reactions near the eta production threshold, aiming to identify bound states.

Contribution

It introduces an experimental approach with high statistics and acceptance to detect eta-mesic helium, providing preliminary data analysis results.

Findings

No definitive eta-mesic helium signal observed yet.

Established upper limits for eta-mesic helium production.

Demonstrated the effectiveness of the ramped beam technique.

Abstract

We performed a search for 4He-eta bound state with high statistics and high acceptance with the WASA-at-COSY facility using a ramped beam technique. The signature of eta-mesic nuclei is searched for in dd -> 3Henpi0 and dd -> 3Heppi- reactions by the measurement of the excitation functions in the vicinity of the {\eta} production threshold. This paper presents the experimental method and the preliminary results of the data analysis for dd -> 3Henpi0 process.