Indication of a strange tribaryon S^+ from the ^4He(stopped K^-,n) reaction

TL;DR

This paper reports the experimental observation of a new strange tribaryon state, S^+(3140), formed in the ^4He(stopped K^-, n) reaction, with specific mass and width measurements indicating a novel hypernuclear state.

Contribution

The study provides the first evidence of the S^+(3140) tribaryon, expanding the understanding of strange baryonic matter and hypernuclear states.

Findings

Observation of a neutron spectrum enhancement indicating S^+(3140) formation

Measured mass of S^+(3140) at 3141 MeV/c^2 with a width less than 23 MeV/c^2

S^+(3140) is approximately 25 MeV/c^2 higher than the previously observed S^0(3115)

Abstract

We measured the neutron time-of-flight spectrum in the ^4He(stopped K^-, n) reaction by stopping negative kaons in a superfluid helium target. A clear enhancement was observed in the neutron spectrum, which indicates the formation of a strange tribaryon of charge +1 with a mass and width of M = 3141 +/- 3 (stat.) +4/-1 (sys.) MeV/c^2 and G < 23 MeV/c^2. This state, denoted as S^+(3140), is about 25 MeV/c^2 higher than the previously observed S^0(3115) T=1.