Speaker
Description
This work focuses on investigating the first excited state ($J^{\pi} = 0^{+}$) of the $^{4}$He nucleus, the $\alpha$-particle. This excited state, probably associated with a four-body Efimov state, is found between the $p\,+\,^{3}$H and $n\,+\,^{3}$He thresholds, allowing for the use of coupled-channels formalism. It is thought to have a $3+1$ halo structure, making it suitable for investigation using a Halo effective field theory framework. This resonance may influence the $^{3}$H($p,e^{+}e^{-}$)$^{3}$He reaction and shed light on the ATOMKI anomaly reported by Krasznahorkay et al., where an excess of produced lepton pairs suggests the existence of a new boson, with an approximate mass of 17 MeV, and that can be a possible candidate for dark matter.
