Searching for η-mesic Helium with WASA-at-COSY facility

Abstract

The search for the 4He-η and 3He-η bound states was performed with the WASA-at-COSY facility using a ramped beam technique in 2008, 2010 and 2014, respectively. The 2008 and 2010 data analyses has already been completed and resulted in the upper limits for the total cross sections for the η-mesic 4He production in dd → 3Henπ0 and dd → 3Hepπ− processes. No narrow structure which could be interpreted as a bound state was observed. The experiment carried out in 2014 collected the largest data sample for 3He-η in the world. The data analysis is in progress. This article presents results of the 2010 data analysis and preliminary results of the 2014 data analysis.