BBN catalysis by doubly charged particles

Abstract

We consider primordial nucleosynthesis in the presence of hypotheticalquasi-stable doubly charged particles. Existence of X –– withmacroscopic lifetimes will lead to the formation of its bound states with4He and otherlight elements, significantly facilitating the subsequentformation of lithium nuclei. From observational constraints on maximumallowable amount of lithium, that we update in this work, we derivestrong constraints on the abundance and lifetime of X ––. In alikely cosmological freeze-out scenario with temperatures initiallyexceeding the mass of X ––, the BBN constrains the lifetime of theseparticles to be less than about 100 seconds. For parametrically longlifetimes, lithium abundance data constrain X –– abundance to be lessthan 10-9relative to protons, regardless of whether these particlesdecay or remain stable. Stable particles could saturate the dark matterdensity only if their mass is comparable to or in excess of1010 GeV, and most of X –– will be found in bound states withberyllium nuclei, so that chemically they would appear as abnormallyheavy helium isotopes.