A quick question:

Is the appearance of the cosmological constant the puzzling part, or the smallness of it compared to other typical scales (Higgs VEV for example).

Because given (semi-classical) gravity, it is necessary to introduce a constant term in the lagrangian, that may have a finite value.

Also, is there anyone who has calculated the flow of this constant given some particle content in the universe (say only the fermion sector with Dirac mass, or even the full SM) to maybe explain the smallness in a natural way?