Towards a minimal natural standard model

Apart from neutrino masses and dark matter, the standard model matches most of the particle data. But it has a "naturalness" problem (and a hierarchy problem and a finetuning problem; I need to understand the nuances of their relations better).

When discussing minimalism, I mentioned the "new minimal standard model". The authors say explicitly that they will not care whether their parameters are finetuned, they will only care about matching the data.

In this era of absent supersymmetry, revisionist perspectives on naturalness and the hierarchy problem are gaining ground. But it's also true that finetuning can be eliminated without introducing the whole supersymmetric spectrum. All you need are "top partners" and maybe higgsinos.

In the discussion of Weniger's 130 GeV gamma ray line, the higgsino is one of the least popular candidates; nonetheless, there are a handful of papers trying to get dark matter, and the line, from higgsinos. So today's question is this: Can we construct a natural extension of a minimal beyond-standard-model theory, in which a higgsino-like particle both supplies the dark matter, and helps to stabilize the mass of the Higgs?

Partly interacting warm dark matter

Perhaps this is a better way to approach it: the dark matter is mostly "warm dark matter" with a keV-scale mass, but there is an interacting dark-matter subsector about as big as the baryonic sector, which is the source of all the GeV-scale signals.

Towards a 3+4 minimal model

I have a framework now: standard model, plus four right-handed neutrinos, plus a new scalar for inflation.

The four new neutrinos are there to provide dark matter on four scales: keV for the "warm dark matter" that may be the bulk of it, O(10) GeV for the CDMS signal (Dan Hooper also argues that there are galactic-center emissions consistent with a 10 GeV particle), O(100) GeV for the Fermi line, O(300) GeV for the PAMELA/AMS positron excess.

At this point I have little idea how well this will fare. I am especially unsure of whether GeV-mass sterile neutrinos are suitable for producing any of the DM signals; but there's lots more to worry about too. The point is just that it's a place to start, a framework to test. It can be replaced with something more complex if it just can't work.

Expect progress in developing this framework to be slow-to-nonexistent.