Cosmological Strangeness Abundance

Abstract

We investigate the strange particle composition of the early Universe in the hadron epoch $T_h\approx 150\ge T\ge 10$\,MeV. We study strangeness yield in thermal and chemical equilibrium constrained by prescribed entropy per baryon in a charge neutral and strangeness neutral $⟨s-\bar{s}⟩$ Universe. Turning to kinetic processes in a Hubble expanding Universe, we determine conditions at which individual strangeness producing reactions fall out of detailed balance between decay and back-reaction strangeness production rates in presence of decreasing temperature $T$; we allow for weak, electromagnetic, and strong interaction processes. The weak interaction ${\mu }^{\pm }+{\nu }_{\mu }\to K^{\pm }$ freezeout is at $T_f^{K^{\pm }}=33.8\mathrm{MeV}$; the electromagnetic process $l^{-}+l^{+}\to \varphi$ freezeout is at $T_f^{\varphi }=23\sim 25\mathrm{MeV}$; and the hadronic reaction $\pi +\pi \to K$ freezeout is at $T_f^K=19.8\mathrm{MeV}$.

7 pages, 6 figures

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