Searches for Branons at LEP

Branons are natural dark-matter candidates predicted by theories with extra dimensions. They correspond to the fluctuation of a three-dimensional brane along the extra dimensions and could be the first manifestation of this new physics in scenarios where gravitons are not accessible at high-energy colliders. Two searches performed with the L3 detector at LEP for branon production in the single-Z and single-photon channels are discussed. Their results allow to derive the most stringent limits on the possible existence of branons.