Search for the η mesic He 3 in the pd→dpπ0 reaction with the WASA-at-COSY facility

Abstract

The excitation function for the pd→dpπ0 reaction has been measured by WASA-at-COSY experiment with the aim of searching for He3-η mesic nuclei. The measurement in the vicinity of η meson production was performed using a ramped proton beam. The data analysis and interpretation was carried out with the assumption that the η mesic helium decays via the formation of an intermediate N∗(1535) resonance. No direct signal of the η mesic nucleus is observed in the excitation function. We determine a new improved upper limit for the total cross section for the bound state production and decay in the pd→(He-3η)bound→dpπ0 process. It varies between 13 nb to 24 nb for the bound state with width in the range Γ(5,50) MeV. © 2020 American Physical Society.