just want to share one graph and explain it a little

 

This is from resonaances.blogspot.com, from here: http://resonaances.blogspot.com/2016/09/weekend-plot-update-on-wimps.html

What the curvy lines, the CRESST, CDMSlite PandaX and Lux lines are the constraints from direct detection, if you google the various acronyms above you can find out more about the experiments, but mostly they are large underground tanks of various substances which should be able to detect dark matter and of course they detect neutrinos too.  You might think, well if the universe is so full of dark matter what is the problem detecting it.  The thing is we don’t live in empty space we live right next to this huge ball of gas called the sun.  There is another weakly interacting particle that comes from the sun and a few orders of magnitude more of neutrinos pass through our body every second compared to dark matter.  I did the calculation a while ago, so while there might be 100 billion or so neutrinos passing through the human body every second there are “only” a few billion dark matter particles passing through our body every second.

That gray thing in the graph called the “v floor” is the theoretical lowest limit that dark matter detectors can go.  At that point due to neutrino scattering you can’t go any lower.

 

Ok, now look at that Z portal g=1, that is the model which we have been using ever since dark matter was discovered in order to calculate from the microwave background radiation how the universe grew.   This is a log chart.   That model . . . . which we still use, because we don’t really have any simple alternative, is about 1,000,000 times higher than our current direct detection limits.  We should have found wimps a long long time ago.  But nothing has been found.

I had always figured that we could just build bigger and bigger wimp detectors here on earth but it looks like we are almost at the limit and no dark matter particles have detected at all and while I guess it can still be found in that tiny little slice it doesn’t seem likely at this point.

It seems that the only way to go forward now for dark matter detection now that we have almost reached the limit is astrophysical observations.

Go read the link above for more, it’s a short read.

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