Constraints on Composite - Models Effective

We give a brief review of the existing bounds on effective couplings for excited states (e * , ν * , u * , d *) of the ordinary quarks and leptons arising from a composite model scenario. We then explore the phenomenological implications of the hypothesis that the excited neutrino ν * might be of Majorana type. Recent bounds on the half-life of the ∆L = 2 neutrinoless double beta decay (0νββ) are used to constraint the compositeness effective couplings. We show that the bounds so obtained are roughly of the same order of magnitude as those available from high energy experiments.