Heavy hadrons of 4th family hidden in our Universe and close to detection?

Metastable quarks of 4th generation are predicted in the framework of heterotic string phenomenology. Their presence in heavy stable hadrons is usually strongly constrained; however, their hidden compositions in heavy doubly charged baryons (considered here) are found to be still allowable: we have studied their primordial quark production in the early Universe, their freezing into cosmic heavy hadrons, their later annihilation into cosmic ray as well as their relic presence in our Universe and among us on Earth. If the lightest quarks and antiquarks of the 4th family are stored in doubly charged baryons and neutral mesons, their lifetime can exceed the age of the Universe; the existence of such stable particles may escape present experimental limits while being close to present and future experimental tests. On the contrary, a primordial abundance of lightest hadrons of the 4th generation with charge +1 cannot decrease below the experimental upper limits on anomalous hydrogen and therefore (if stable) it is excluded. In both cases their possible search is a challenge to present or future accelerators