Search for η-mesic Helium with the WASA-at-COSY detector

¹ Institute of Physics, Jagiellonian University, Cracow, Poland
² Institut fur Kernphysik (IKP) and Jülich Center for Hadron Physics (JCHP), Forschungszentrum Jülich, Germany

^a e-mail: wojciech.krzemien@if.uj.edu.pl

Abstract

A search for the ⁴He − η bound state via exclusive measurement of the excitation function for the dd → ³Hepπ⁻ reaction, was performed at the Cooler Synchrotron COSY-Jülich with the WASA-at-COSY detection system. The data were taken during a slow acceleration of the beam from 2.185GeV/c to 2.400GeV/c crossing the kinematic threshold for the η production in the dd → ⁴He η reaction at 2.336 GeV/c. The corresponding excess energy in the ⁴He − η system varied from −51.4 MeV to 22 MeV. The shape of the excitation function for the dd → ³Hepπ⁻ was examined. No signal of the ⁴He − η bound state was observed in the excitation function.