Dark Matter in the Standard Model?

We critically reexamine two possible dark matter candidates within the Standard Model. First, we consider the uuddss hexaquark. Its QCD binding energy could be large enough to make it (quasi)stable. We show that the cosmological dark matter abundance is reproduced thermally if its mass is 1.2 GeV. However, we also find that such a mass is excluded by the stability of oxygen nuclei. Second, we consider the possibility that the instability in the Higgs potential leads to the formation of primordial black holes while avoiding vacuum decay during inflation. We show that the nonminimal Higgs coupling to gravity must be as small as allowed by quantum corrections, |ξH|