Search for eta-mesic helium using the WASA-AT-COSY detector

TL;DR

This paper reports on a search for eta-mesic helium nuclei using the WASA-AT-COSY detector, involving measurements of the dd->3Heppi- reaction to identify potential bound states.

Contribution

The study presents the first experimental search for 4He-eta bound states with a detailed measurement setup and data analysis at COSY.

Findings

Data collection is complete and under analysis.

No definitive signal of eta-mesic helium observed yet.

Method demonstrates the feasibility of such searches.

Abstract

We conduct a search for the 4He-eta bound state with the WASA-at-COSY facility via the measurement of the excitation function for the reaction dd->3Heppi-. In first experiment performed in June 2008, we used COSY deuteron beam with a slowly ramped beam momentum corresponding to a variation of the excess energy for the 4He-eta system from -51.4 MeV to 22 MeV. Here we report on the status of the measurement and the data evaluation.