Dual superfield approach to supersymmetric mechanics with spin variables

We consider a reducible N = 4, d = 1 multiplet described by a real superfield as a coupling of the mirror (1,4,3) and ordinary (3,4,1) multiplets. Employing this so-called long multiplet , we construct a coupled system of dynamical and semi-dynamical multiplets. We show that the corresponding on-shell model reproduces the model of Fedoruk, Ivanov and Lechtenfeld presented in 2012. Furthermore, there is a hidden supersymmetry acting on the long multiplet that extends the full world-line supersymmetry to SU(2|2). In other words, the N = 4 long multiplet can be derived from an irreducible SU(2|2) multiplet.