Hunting the elusive $X17$ in CE$\nu$NS at the ESS

Joakim Cederkäll, Yaşar Hiçyılmaz, Else Lytken +2

The so-called $X17$ particle has been proposed in order to explain a very significant resonant behaviour (in both the angular separation and invariant mass) of $e^{+}{e}^{-}$ pairs produ…