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Dark Matter : Xenon1T

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posted on May, 31 2018 @ 01:46 PM
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I half expected someone else to post up about this but, alas, no one has. This is quite possibly because the collaboration in question decided not to go the fanfare route and advertise a big announcement months in advance and get everyone all excited.

The Xenon1T experiment unblinded its data and produced a limit on dark matter cross section, meaning they don't appear to claim any dark matter observation.

They are currently the world limit holder, overtaking the previous experiment LUX with a limit on the WIMP cross section of of the order 10^-47 at 50GeV

It is an interesting result, I sat through a seminar this morning discussing the detector and the result. The physics campaign for this experiment appears to have been cut short, the original plan would have been a multi-year run, though technical difficulties plagued the experiment from the outset.

The experiment is a Dual Phase Liquid Xenon Time Projection Chamber. A Time Projection chamber is a rather sci-fi sounding label though it is the simplest way of describing how the detector works, which is that it, Time Projects charge in order to figure out z height of the origin of the charge.
The detector is made of a pressure vessel and cryostat, and inside this is placed a cylinder volume formed out of rings, i think in this case copper. Between each ring is a resistance, say a few mega-ohm. On the bottom and top of the rings, the volume is capped with a meshes (the meshs is coupled via a resistance also) A high voltage is applied to the bottom mesh, and the top is grounded. What this does is create a uniform electric field inside the cylinder. Ideally you want that pointing toward the bottom, this way, any ionization produced inside the volume will drift in the electric field, toward the top mesh.

The ground plane remains below the fill level of the liquid, and placed a small distance above the liquid level, in the gas space, is yet another mesh, also at high voltage, but opposite polarity as the bottom mesh. When the electrons reach the surface of the liquid, this is where the interesting stuff happens.

Basically, the detector is read out via single photon counting PMTs, you recieve primary signal during the actual event, when the Xenon is ionized by some source and the Xenon scintillates, producing light. When the charge is extracted from the liquid, into the gas space, it produces another signal, a secondary signal. You can use this signal to figure out things like... the type of event it is, how much energy was contained in the event... etc. The time between the primary and secondary signal is the 'time projection' part, and if you know the field strength of your field cage, then the drift velocity is roughly constant, thus you can figure out exactly where in the detector the event happened.

Long story short, A detector of this type is very hard to operate and maintain, it is a credit to the experimentalists to have built one this large and operated it successfully. They did have a few issues down the way however... one being a seismic event which appeared to have tilted the field cage slightly, which means the charge gain across the detector is not equal (path length through liquid and knowing the liquid level in relation to the ground and anode meshes sets this). The other issue they had was a degradation of their PMTs as the experiment went on, with them appearing to show signs of growing afterpulsing with a characteristic time scale equal to that of Xenon, meaning somehow the Xenon gas was penetrating into the PMTs (usually vacuum) and such, the experiment was rumoured to have a finite lifespan... we see that result today.

www.xenon1t.org...

All however is not lost, there are other running experiments in the form of PandaX (Very similar design) in china, who will likely put out results competitive to the Xenon1T result soon (2-3 months?). On the opposite side of the spectrum, there is a Liquid Argon Experiment operating in Canada currently who will be working on a similar release. This one is close to my heart as I built the Argon Purification system for it. Due to the early retirement of Xenon1T, the DEAP-3600 experiment could take the world limit, abet for a short period of time.

It too has had its issues. Building these large scale detectors is a massive challenge.

I have a fair amount of knowledge of the operation of these detectors, so any questions and comments or discussion are welcome, I did only give a very brief and cut down summary of how the whole show works. There are lots of areas and concepts that can be probed for dark matter... so... not dead yet...
edit on 31-5-2018 by ErosA433 because: (no reason given)




posted on May, 31 2018 @ 03:02 PM
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a reply to: ErosA433

Thanks ErosA433.



posted on May, 31 2018 @ 04:04 PM
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a reply to: ErosA433

So what candidate DM particles remain after considering these new constraints? Over time I'm getting more confident that dark matter is an illusion caused by inverse gravitational lensing.
edit on 31/5/2018 by ChaoticOrder because: (no reason given)



posted on May, 31 2018 @ 05:50 PM
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a reply to: ChaoticOrder

Scientists claim that only 5% of the universe is visible and the rest of the universe is composed of dark matter (25%) & dark energy (70%). They can't isolate dark anything but need it to shore up their computations.

Maybe at some point they will realize their models are bunk. They have to create this dark something to make their formulas work. Is it possible their entire approach is in the wrong direction? Time to start thinking outside of the box. Electric universe anyone?



posted on May, 31 2018 @ 05:52 PM
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a reply to: ChaoticOrder

It is an interesting question, firstly, we have not covered the whole parameter space, we are in a rather unfortunate situation where the parameter space is fairly large. For particle dark matter It looks a bit like this



on the y axis is cross section, its basically a measure of interaction probability or interaction strength.

We have pretty much ruled out Neutrinos, they are too light, and move too fast to have the properties we observe from astronomy and astrophysics. The next easiest to look for are WIMPS and Axions, Both those fields are getting stuck into their perspective search regions, WIMP searches are more mature and with the next, or next to next generation might basically have covered the whole parameter space. Next up would be Axions, these seem like an exciting candidate.

Axions are a particle or consequence of a direct coupling between light and the magnetic field to spontaneously produce a light particle, or axion... requires only small modification to maxwells equations and could make up some of what we observe today, though, it is unclear, due to their mass, if they could make up the whole.

There are other things such as massively undercounted Black Hole Remnants, though again this is largely unclear, the search in astrophysics for such candidate objects make up possibly backgrounds in astrophysics experiments, the search continues (these would be things like MACHOS). Q-Balls on there are again a bit tricky as we should see evidence for them in astrophysics, though we are yet to really get stuck into a proper search due to lack of instrumentation i think.

So for particle dark matter, the field is still open.


It is hard to say, based on the observational evidence and physics motivations exactly what it is, the WIMP solution is simple and well motivated and fits with observational evidence very very well. Of the parameter space covered, the current large scale detectors focus largely on heavy dark matter, in the GeV range, Xenon most sensitive at around 50, while DEAP most sensitive around 100 GeV, the sensitivity at low mass drops off sharply due to the kinematics and energy threshold of the detector medium.
So the next exciting field parhaps should heavy WIMP searches not produce anything, would be light WIMPs, down in the MeV range. There are experiments (mostly novel technology and crystal bolometers) that are coming online in the next few years that aim to really smash that region of interest.


On inverse gravitational lensing, Im not sure exactly what you mean given the measurements of the observed effects of so called dark matter have been measured and characterised in both in the movement of whole galaxies and movement within galaxies using doppler like effects (could be what you are getting at, sort of a tired light affect) and in strong and weak gravitational lensing. In which you observe lensing effects from for-ground objects on the background. These effects are wavelength independent largely.

Both methods appear to give the same results however, that galaxies have large extended distributions of matter that do not appear to be baryonic, and galaxy clusters show the same for each galaxy and even turn up material separated from things like intergalactic hot gas etc.

Issue with a lensing effect distorting what we observe and measure in terms of mass, I am unsure that such an effect is supported by evidence, if it was the case for example, spiral galaxies would have very different lensing profiles to elliptical due to the matter distributions... truth is, they don't, not only this but the galaxies spinning much faster than they should be expected to, is observed pretty much universally, and has features depending upon galaxy type though the dependancy on the dark matter observation is primarily not coupled directly to the problematic reasons of galaxy rotation.

(Example - rotation curves often have a dip and a rise when taking observations moving from the core to the start of the spiral arms... this dip is not present in all galaxies and appears to depend entirely upon observable structure, such as if a galaxy is a bar shaped core, this part of the galaxy rotation is completely in fitting with theory without dark matter. It is also the primary source of mass for lensing. as you move out in the arms, this is where there are issues, but the growth of observable mass does not account for the fast rotation, and is not a primary factor in the lensing effect compared to the core.)



posted on May, 31 2018 @ 06:04 PM
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a reply to: ClovenSky

Issue with electric universe is that, it doesn't work and predicts nothing that the current models don't. There are also observations out there which absolutely don't fit with the electric universe (of what little tangible theory there is) Such as a region of space, with little to few stars, and yet, has significant lensing effect on the background and once more, what stars are there, move too quickly to be bound. A so called Dark Matter Galaxy.

The electric universe theory has never been able to actually prove itself as an actual working theory. All is ever shown of it is some nice drawings and false claims in regard to the current state of play in the mainstream. Too often saying "Electric Universe theory fixes this problem" and then go on to not show a single reason why or experimental data to support any claims.

So no... I really doubt Electric universe theory is the key to this, and no, before anyone says "But electric fields and magnetic fields are ignored by the mainstream" No, they are well known and can be measured in polarization of different active galactic sources.


If you understood the history and the measurements, rather than making these somewhat tired throw away comments about "oh they are just fudge factors" you would maybe see that it isn't as simple as just having some throw away factors, but is a commonality between a multitude of experimental observations that all point to a single thing... which is... Matter is not doing what it should be doing at all on very large scales, and our observations on these scales suggest actually that our current gravitational models seem to be pretty damn good. MOND is definitely broken and doesn't work given the observation of dark galaxies. So what's it to be? Do we just throw away everything and say "magic" or do we do experiments...

Personally, i prefer experiments.

With experiments I should make it clear that there is no assumption of observation (other than the assumption that there is a coupling to the standard model), just experimentation that says "We are targeting a specific particle, and we are going to build a detector we believe gives us a good chance of observing an interaction of type x that we can build and not mis-identify the interaction with backgrounds such as natural radiation, cosmogenic radiation or detector specific effects... and if we don't observe something, we will set a limit, and propose a different experiment or approach" Science isn't limiting its detector technology, or its approaches, right now there are searches covering

-Underground Physics with about 5 fundamentally different detector designs, technology and readout methods
-Astrophysical searches looking for annihilation signals or other excesses in the observed background, largely x-ray and gamma ray spectroscopy
-Axion searches using resonant cavities or solar telescopes.

It truly is a search which scientists want to solve and are trying to target the most probable areas before throwing in the towel for a almost completely 'theoretical' model.


edit on 31-5-2018 by ErosA433 because: (just extra justification)

edit on 31-5-2018 by ErosA433 because: (no reason given)



posted on May, 31 2018 @ 07:57 PM
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a reply to: ErosA433

You know whats beautiful? Time will tell. We will see how well the theoretical physics and math hold up. Most of the complex science, math and physics doesn't even relate to reality anymore. They can create and make up almost anything since they don't have to provide any examples or tie it into our reality.

I understand that the concrete examples aren't provided by the electric theory either. But they are just getting started. There were a lot of predictions about mars made by electrics that proved to be true once we were able to study the planet closer. There have been predictions made by Thornhill on the effects of a comet striking jupiter's atmosphere that turned out to be a lot more accurate compared to mainstream cosmology's expectations for shoemaker-levy 9.

I am patient. This will be a lot of fun.



posted on Jun, 1 2018 @ 12:12 AM
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a reply to: ErosA433


On inverse gravitational lensing, Im not sure exactly what you mean

I assumed you would have seen at least one of my threads on the topic. It's quite an old concept which arises within a universe where bimetric relativity applies. It can explain the flat rotation curves of galaxies as well as the increased mass we measure based on the lensing intensity. See the "Universe" link in my sig.



posted on Jun, 1 2018 @ 01:32 AM
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a reply to: ChaoticOrder

Thanks for the link, i gave it a read and it would appear to now make sense, though it sort of requires or stipulates that the negative mass exists in a shell like halo around each galaxy and between them. Its an interesting idea though lens de-convolusion, in which you look at external lensing effects so figure out the mass shape of a gravitational lens don't appear to show this structure if i remember correctly. It is possibly why its disfavoured and some what of a niche topic, as in your own thread you say, negative mass and negative energy hasn't quite been shown to exist.

Interesting concept though, was a good read and is, probably more plausible than the EU models.

And on that note

None of the EU theories predictions in regard to the Rosetta probe happened... i remember that one quite clearly... I also seem to recall much of the predictions of what would be standard science, were largely confirmed during the mission. Issue with the claims by Thornhill is that much of them are observational descriptions that have little to nothing to do with any theory, they are simple descriptions of things with a tag at the end saying "I predicted that"

Like i said, not much of the theory is workable in a transparent manner other than to Thornhill when ever he wants to get paid to do some invited talks or, get people to pay and attend an echo chamber like conference.

Will be interesting in reference to Shoemaker levy 9, how the break-up into a long stream of multiple parts was predicted by the mainstream, and fit perfectly with stresses applied to a semi-solid/porus material like water ice saturated with other cryo-voletiles passes well within the Roche limit of a body like Jupiter.... but, you know, all of what i see of EU is after market sales rather than actual predictions... and as i say... if anyone could actually point to references of the theory that'd be great, because my respect for it is quite low given all it a massess too at the moment is a scattering of self referenced websites, incorrect standard model knowledge and cherry picked examples and the ramblings of a man who says he can predict every observation... and yet cannot at all provide any tangible model of say... how the planets orbit like they do in a stable manner without the potential differences being so insane you would expect enormous electrically driven plasma arcs everywhere.... the sheer level of electron imbalance would be painfully obvious, yet, it is not... so yeah... it is quite fun watching people attribute everything observation to a none-existant prediction and model.

Too much of
"Oh yes... we see X-rays... EU theory predicts that, the standard model doesn't"
Ignoring the fact that the standard model totally predicts it too... and can give you a model of how and why... and the EU theory people either go "Watch this youtube video" or "Pay $$$ to come and see this conference talk"



posted on Jun, 1 2018 @ 02:06 AM
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originally posted by: ErosA433
a reply to: ChaoticOrder

Thanks for the link, i gave it a read and it would appear to now make sense, though it sort of requires or stipulates that the negative mass exists in a shell like halo around each galaxy and between them.

It only exists between galaxies because positive mass repels negative mass. The halo around galaxies is a cavity of negative matter, a lack of negative mass, and taking away negative mass is equivalent to adding positive mass, which is why we see the surprisingly strong lensing effect around galaxies, hence inverse gravitational lensing. Scroll down the page a bit and you'll see I post some diagrams which make the idea a lot clearer. There are also several other things this model can easily explain which I didn't cover in that thread, such as the cosmological constant problem, the cuspy halo problem, the missing satellite problem, etc.


Interesting concept though, was a good read and is, probably more plausible than the EU models.

Yeah I don't think electric universe models hold much weight either, and they certainly don't help much to solve the issues of dark matter or dark energy. Also check your PM's.
edit on 1/6/2018 by ChaoticOrder because: (no reason given)



posted on Jun, 1 2018 @ 12:28 PM
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Thanks for that, ill add it to my reading list, it is quite an interesting way around of thinking about the dark matter problem, that said, I suspect if it is (the negative matter solution in this thought experiment) the case we should see some affect in rouge stars or smaller dwarf galaxies out there.

if not still be able to detect particle like nature or observe some affects in the lab still. I guess the assumption is that it doesn't couple to the standard model except gravitationally.



posted on Jun, 2 2018 @ 07:38 AM
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a reply to: ErosA433

Always great to see your posts. Great thread. I do have some questions, as I am a novice in the sub-specialty of the OP:



this way, any ionization produced inside the volume will drift in the electric field, toward the top mesh.....if you know the field strength of your field cage, then the drift velocity is roughly constant

In vacuum any ionization would continually accelerate in a constant electric field, so does the dE/dx force from passing through the Xenon result so the "drift velocity is roughly constant"? (I could work out dE/dx, but I suspect you already know the answer for me, and that would add clarity for me and perhaps others.)




you recieve primary signal during the actual event, when the Xenon is ionized by some source and the Xenon scintillates, producing light. When the charge is extracted from the liquid, into the gas space, it produces another signal, a secondary signal.

At first it occurred to me that if the Xenon scintillates because of the ionization, and the ionization flows upward because of the electric field, that you'd get a continuous stream of primary events, not just a single primary event. But after thinking about it, I am guessing it only scintillates during the initial ionization. That would mean to me that as the ionization drifts upward it never gets enough energy to further ionize other Xenon along the way - do I have that right? Or does each event involve several scinitillations? Also, I would expect the scintillations to go in any direction at all, so I believe it must have PMTs in all four pi steradians of coverage - right? It might be helpful also if you could mention what the cause is for the second light signal as it goes through the gas (I'm guessing the pressure is just right so that enough acceleration now occurs due to the lower dE/dx that you get a second ionization?).




thus you can figure out exactly where in the detector the event happened.

I can see how you can figure out where longitudinally the event occurs (reasonably exactly, never exactly exactly of course) but I don't see how you can determine the transverse position, if you only get a single photon for each event that might go off at any angle. I'm also thinking the timing of the photon travel is negligible, and that the ionization is all moving at non-relativistic speeds. Is that right?




You can use this signal to figure out things like... the type of event it is, how much energy was contained in the event... etc.

It would be helpful to mention how all that can be figured out.

And what is a Q-ball?

--

Also, what is the theory on how the ionization occurs in the first place? I am guessing they are looking for a random WIMP to pass through the Xenon, and that somehow produces ionization. But what is the theory that makes Xenon a good fit for a 50 GeV WIMP? Is this reasonably simple to describe? Or does it involve the full glory and complexity of the standard model Lagrangian to make the predictions? Since the matter is "dark" I'd expect it not to interact much at all with normal matter in the first place. While they are proposed to interact gravitationally, any gravitational effects would be immensely weak for single particle events, so I can't imagine its gravity. Perhaps you can shed some light on how things are expected to produce the ionization?

And then there is the issue of background. I would expect that there would be significant cosmic ray background. I am guessing a WIMP signature would differ from signatures of other sources of ionization?

--

Well thanks again, as this is interesting. And if you get a chance, I hope you can watch and comment on the video I produced (my most recent ATS thread) as I always appreciate your feedback. At 31 minutes, I am afraid the video is a tad long, so I don't think many have watched it. It went over extremely well at Brookhaven National Lab, and my colleague said I should put together a 2-3 minute summary, since if well done it might generate enough interest for people to spend the 31 minutes. 2-3 minutes will be tough of course, but I'm thinking about how to do it. The problem is that you can't replace the standard model with a tweet!




posted on Jun, 2 2018 @ 08:08 AM
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Everything I have heard or read in the last few months has said dark matter is dead even though huge amounts of money has been spent on trying to detect the particle responsible.. Some of this is over 7 months old so I may be out of touch ?
www.youtube.com... event=video_description&v=GuwkbGAnkE0
www.youtube.com... vent=video_description&v=GuwkbGAnkE
youtu.be...


youtu.be...

edit on 727ndk18 by 727Sky because: (no reason given)



posted on Jun, 2 2018 @ 01:59 PM
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a reply to: 727Sky

Im not completely sure what you believe amounts to 'Huge amounts of money'

Most of these experiments are barely a drop in the water, Dark matter searches are pretty much free. Even then, most of the cost of them goes into industry and back into the economy, so the numbers arn't as simple as "cost" as though its money that ended up in the wallet of some billionaire and not into the greater good.


No, Dark Matter isn't dead at all, it depends where you get your information from, and the sources you frequent. If you only listen to the alt-science movement, you would be easily convinced that actually they know everything and the mainstream is spinning its wheels faking everything.

There are real experiments which are very very well understood being performed, with more science in their measurements than any of what has been produced by any proponent of EU, Seriously... an experiment such as DEAP requires such massive attention to detail that when people dismiss them as 'pointless' it kinda makes me smile, as it shows a huge level of ignorance.

People it seems would rather enjoy soundbites than actual science.



posted on Jun, 2 2018 @ 02:36 PM
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Thanks delbertlarson ill try to answer/discuss each point or question.


In vacuum any ionization would continually accelerate in a constant electric field, so does the dE/dx force from passing through the Xenon result so the "drift velocity is roughly constant"? (I could work out dE/dx, but I suspect you already know the answer for me, and that would add clarity for me and perhaps others.)

Admittedly this wasn't explained very well, what actually happens is that the ionization is stationary, though because of the electric field, it begins to accelerate. However depending upon the field strength, the gas pressure (in this case it is liquid) the mass and temperature of the target, the drifting ionization reaches a terminal velocity due to the amount of energy gained moving through the field, and the loss caused by scattering from the target. The ionization thus reaches a terminal velocity very rapidly and remains at that velocity. This can result in reduced event reconstruction accuracy if an ionization track occurs very close to the readout, or crosses the readout. It will result in a kink in the arrival of charge.

The drift field also affects things like, how much the ionization smears out due to collisions, and what the energy threshold is, because if the field is too low, the ionization will recombine too rapidly



At first it occurred to me that if the Xenon scintillates because of the ionization, and the ionization flows upward because of the electric field, that you'd get a continuous stream of primary events, not just a single primary event. But after thinking about it, I am guessing it only scintillates during the initial ionization. That would mean to me that as the ionization drifts upward it never gets enough energy to further ionize other Xenon along the way - do I have that right? Or does each event involve several scinitillations? Also, I would expect the scintillations to go in any direction at all, so I believe it must have PMTs in all four pi steradians of coverage - right? It might be helpful also if you could mention what the cause is for the second light signal as it goes through the gas (I'm guessing the pressure is just right so that enough acceleration now occurs due to the lower dE/dx that you get a second ionization?).

Yeah the scintillation process in something like a Noble (in this case Xenon) which for a TPC like used has to be ultra pure, in the parts per billion to trillion purity. In something like this, state any light produced by atomic Xenon would be re-absorbed. The interesting part is that when ionized, they produce excited state short lived molecules. These can radiatively decay back to atomic Xenon and produce UV photons (in the case of Xenon, around 170-180nm). The drift field supresses this process as it is limited to the location of the primary ionization site and is a process produced by the atoms themselves. These ions will drift (opposite direction to the electrons... and more slowly) and such will be drifted in a single direction and less likely to collide with each other to form these 'dimers' when they are moving. Light is isotropic as you say. though typically TPCs are read out at the ends due to light loss from coverage by the field cage structure.

You point at something important also, as the electrons drift, if the field is low, they will not further ionize the target simply drift their way to the readout plane. It is at the readout plane that the field is very high, and the aim is to do exactly what you say... produce gain from avalanche amplification.



I can see how you can figure out where longitudinally the event occurs (reasonably exactly, never exactly exactly of course) but I don't see how you can determine the transverse position, if you only get a single photon for each event that might go off at any angle. I'm also thinking the timing of the photon travel is negligible, and that the ionization is all moving at non-relativistic speeds. Is that right?


The longitudinal (or z height) comes from the difference in the arrival times at the readout plane as you say, so that gives you the height. If you detector is lets say 50cm in height, and your drift velocity is 50cm/micro second, then your electronics has to be able to digitize the signal at better than 1/50 microsecond per bin to be able to get about 1cm resolution. Ultimately Nano-second accurate digitization is fairly easy these days so, no worries there. In the lateral plane, x-y, its mostly about having a fly eye like structure to your readout... you have say... 100 detectors arranged on your readout plane, and as you say, you get a flash of light that goes everywhere. It will happen almost instantly due to the distance being small and we don't do femptosecond timing so your signal comes all at once. But despite it being in a blob, the solid angle acceptance for each readout module is different and so the flash will be brighter closer to the event.

Now in a TPC like Xenon1T, you don't reconstruct tracks... the tracks are very small, on the order of nanometers. BUT in other TPCs for different experiments, you can reconstruct 3d Tracks... typically though you don't do this with light, you do it with reading out the charge collected at the anode. I do have a photograph however of alphas from Americium decays in a low pressure gas TPC if you are interested...



It would be helpful to mention how all that can be figured out.


This is in reference to figuring out types of events electromagnetic, nuclear recoils. it all comes down to the chemistry of the target and topology of the events. The affect is quite subtle. As i mentioned in the production of scintillation you can produce dimers... these will typically have multiple spin states and as such will decay at different rates. THUS what you will expect is that the S1 (primary) signal will have a shape dependant upon the ratio of these different states. Interestingly, nuclear recoils and electromagnetic events produce different ratios of these states. Thus, it gives you a point of discrimination against these different types. This affect goes on to give different ratios of S2 (secondary) signals also allowing you to separate out the events. Energy is also an obvious one too, radioactive decays will produce a spectrum of energy and such, when you collect all your data you will have events that produce peaks in the energy specturm that you can easily say "Ah yeah, that is Lead 210" for example... you can in some cases do event tagging based on timing... such as Bismuth Polonium.

In Liquid Argon, this affect is enormous (without a TPC, if you just look at light) DEAP gets something like 10^9 discrimination because the excimers form a triplet and singlet spin states... the decay time of these states is 7ns and 1.6microseconds.. the events from nuclear recoils and electromagnetic, look totally different even by eye.



posted on Jun, 2 2018 @ 02:49 PM
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And what is a Q-ball?


Its kinda one of those thought experiments where you say... what is the most stable configuration of something, and then you realize that, you wait, if you theoretically could produce say... a ball of bosons, analogous to an atom say, that is actually a stable configuration, and as such can exist, and have a very long life, and is energetically forbidden to decay... its like that basically. I am totally not an expert on those haha.

--


Also, what is the theory on how the ionization occurs in the first place? I am guessing they are looking for a random WIMP to pass through the Xenon, and that somehow produces ionization. But what is the theory that makes Xenon a good fit for a 50 GeV WIMP? Is this reasonably simple to describe? Or does it involve the full glory and complexity of the standard model Lagrangian to make the predictions? Since the matter is "dark" I'd expect it not to interact much at all with normal matter in the first place. While they are proposed to interact gravitationally, any gravitational effects would be immensely weak for single particle events, so I can't imagine its gravity. Perhaps you can shed some light on how things are expected to produce the ionization?

And then there is the issue of background. I would expect that there would be significant cosmic ray background. I am guessing a WIMP signature would differ from signatures of other sources of ionization?


Big question and sorry the answer is going to be kinda short. The ionization comes from, Elastic scattering, or billiard ball scattering. As you correctly stipulate, it assumes that WIMPs interact in this manner. WIMPS would only be weakly interacting and as such this depends upon the mass of the WIMP and the mass of the target... So how much energy would theoretically be transferred depends upon lots of things, nuclear form factors,velcocity of the sun through the halo, thermal temperature of the halo, even the time of day to some extent.

The scatter basically causes the atom to sort of smash through its surroundings and strip off electrons as it does so.

The sensitivity of the target to the different wimps is completely to do with kinematics, Xenon is heavy, it thus gives you higher target mass, and a higher predicted event rate, as such the turnover point in sensitivity is a bit lower than that of Argon, which is much lighter... as such... Argon you expect a lower rate, kinematically you might think it is more favourable, as you expect more ionisation... but it isnt as massive a factor as you might think and as such, for argon, the sensitivity is better for higher mass wimps for the same level of exposure.

On those sensitivity curves you might see... Xenon cuts deeper into the low mass region, Argon cuts deeper into the higher mass region... so while Xenon1T covers a good deal of the parameter space, DEAP will cut a chunk much better in the higher mass region... making the two experiments quite complimentary at covering the parameter space.


--


Well thanks again, as this is interesting. And if you get a chance, I hope you can watch and comment on the video I produced (my most recent ATS thread) as I always appreciate your feedback. At 31 minutes, I am afraid the video is a tad long, so I don't think many have watched it. It went over extremely well at Brookhaven National Lab, and my colleague said I should put together a 2-3 minute summary, since if well done it might generate enough interest for people to spend the 31 minutes. 2-3 minutes will be tough of course, but I'm thinking about how to do it. The problem is that you can't replace the standard model with a tweet!



I do have much to watch and read over the next few days, im making a reminder list to make sure i can look everything over


Many thanks! hopefully the answers make sense and i didn't fluff anything up
edit on 2-6-2018 by ErosA433 because: (no reason given)



posted on Jun, 2 2018 @ 04:31 PM
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a reply to: ErosA433

Thanks. I learned a lot and things are much clearer now.



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