In the search of Dark Matter.

We look for dark matter based on certain characteristics that.

Sensually have to be true so if we're looking for Column A great article dark matter like wimps.

What we know is that it has to be a stable particle because these are thought to be a cosmological origin so a stable particle it must not interact with the strong world like a magnetic interaction not electromagnetic that's what makes a dark doesn't interact with light and not strong interaction that's a much stronger going to let go magnetic and it would have consequences that would be easily visible so.

And not interacting electromagnetically means neutral so if you look at all the standard model particles and most of them are not stable are many of them have electric charge or like the photon interaction via Lector magnetism.

And it doesn't actually. Leave anything right so it's. Just to be the dark matter that we see. Rules out our most elementary particles. There are other forms of dark matter that are on the words of being ruled out. That that get around mints for example atoms are neutral.

Yet if you can find a way to out of a boy do a bit electromagnetic radiation like in something cold like a true critter like thing it could be dark matter but for elementary particles there really isn't.

No one elementary particle that meets the simple requirements.

So where do we look for we have now.

So the standard ways of looking our own changed one way is to try to make them like it be a Large Hadron Collider and good most popular theory that would predict something that could be equipped like what supersymmetry super to matric is not entirely ruled out of my understanding is that the theoretical model have to strain a little bit to get all our While whips what's been ruled out is mass ranges that go for.

A few cheap easy.

Cheap overseas where that is a few times the mass of the proton to do a few hundred and so that's one of the experiments or the most sensitive so we look to logout in a box that. To me doesn't seem like the most natural.

Region from long ago and the coupling is we're looking at the interaction strength are now weaker than the W. when we have.

Distinct we heard it on the standard weak interaction so it's edging outside the original motivation but that motivation could be stretched a little bit so it's not ruled out yet so the old ways of looking are still valid you try to make them at the ONLY see. You do in direction which was astronomical you look for wimping at the WIP annihilation and so what you're actually observing is standard particles like gamma rays or X. rays or neutrinos or are the electrons or positrons So you look for signals in normal batter coming to the earth that you could argue are resulting from an aisle Asians of which say at the center of the galaxy but all. There's a lot of things can make standard model particles and you have to rule all of those out and that has not been definitively done in any of the many hits him in direct searches. I work on direction or choose which means in the laboratory we've built a detector that should be sensitive to the actual interaction of what we're seeing through the lab.

Given the gravitational constraints if you. Presume A We have graphs we know roughly how many go to our lab because we know roughly how much of the mass of the galaxy is it isn't going to matter and if you assign a mass to them you know how many but the range of possible masses was getting wider not narrower and so that kind of tricky but I remember that with a kind of hundred G.E.V. we have namely a hundred times the proton mass I think if you cup your hands there are a few in there at any moment.

So that's what we're looking for the interaction is expected to be very weak and we have to get rid of all the background but the leading detectors for trying to find this the most sensitive are liquid noble gas like seen on or are gone in a liquid form.

Detector technology it's called a time projection chamber it's kind of a trick a chamber like they have been big guy energy physics detectors but it has to be sensitive to the recoil of a single ad up after it's been struck by a wave and that's what we look for and the direction riches are pushing. Through masses higher then the L.H. he can reach and also to cross sections interaction strengths that are are very weak much weaker than the standard weak interactions and that's the direction we push down in interactions strakes and either or both recently also down in mass so down to a little bit about the approach on up to the mass of a thousand protons.

And those are the direct technologies and those have to be in deep underground labs to shield them from cosmic rays so Darkseid is a liquid or gone kind of projection chamber it is not the most on foot. In the world but Dom Oregon has some advantages over Xenon you know it has some advantages you know which is the world leader argon Darkseid is catching up and there's another Canadian experiment Also coming up why.

So the. Issue here is getting rid of background So background could be anything that either makes an atom look like a.

Good scout or off the nucleus of an atom and make a whole lot of move or a gamma ray from radioactivity could.

Be tracked and electronics from and out of men could fool you into thinking that it's a whole building out of so we have to be able to distinguish those things and with some of the current technology you can distinguish quite well between the signal and the background so it Darkseid we have what we surround it good detector with a neutron detector to extremely sensitive so could you crowd interaction are all gone we can catch it give me other detector and we can distinguish between whether you have a recoiling.

Well or just an electron because of the pattern of white that is made in Oregon.

Simulation it emits light when you have either an atom or electron going through it and the time signature of those light emission pulses is very different for the two so we have a very good background discrimination and that allows us to push to where and rare are possible with good bands and Soledad that's the name of the game it is getting getting rid of that background now it's very low masses where the central committee is sometimes hard right now.

The background issues are more serious and that's why they're not as sensitive but also deliberate to distinguish that. Graham from signal the laboratory gets very difficult and so there are many many very little search is underway right now in fact we just published the most sensitive one at all riled up a few talk about.

What we really can't tell if something is signal or background we just have to make it so low that there's almost nothing seen until that other front here right now in direct search.

For the experiments.

That are certainly have.

An experiment that could actually find dark matter there are or can it only rule it out in the following. If you see a whole bunch of events.

But they could be background and if you can't tell them apart then you're not going to be able to discover where if you see very few events you may be able to rule out where that would get a rate higher than that but if you can't distinguish background you could never discover it.