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The Hardware That Searches For Dark Matter (hackaday.com)
szczys writes: Deep in a gold mine in South Dakota, the Large Underground Xenon experiment waits in the darkness for a tiny flash of light that signals that dark matter actually exists. So far we theorize that it does exist, and have gone to great lengths to build hardware to detect dark matter. Very cold, very pure liquid xenon sits waiting for a dark matter particle to strike the nucleus of a xenon molecule, producing a distinct pattern of photons through scintillation. An array of photomultiplier tubes detect the photons, whose pattern is processed by FPGAs on custom boards connected using HDMI. The experiment has generated a list of properties not possessed by dark matter; running for several years no evidence of the particles interacting with the xenon have been found. But when the data collection concludes this year, a much larger version of the impressive hardware will be built.
Hmmm .... so I'm going to have to stretch my little monkey brain and hopefully someone more knowledgeable can chime in ...
I see reference to WIMPs in the article, so in some ways do we consider Dark Matter to be kind of like a neutrino? All around us but not generally interacting with us?
So instead of there being vast tracts of stuff we simply can't figure out where it is, it's spread throughout?
The overall underground detection mechanism sounds like the Sudbury Neutrino Observatory, or that Ice Cube deal in the Antarctic (Russia?)
I've always thought it wasn't assumed to be floating around us but not interacting, but I ain't no particle physicist.
Is Dark Matter more like neutrinos than not? Or entirely different, but with enough commonality to confuse a layman?
Lost at C:>. Found at C.
How does that work?
Lack of results doesn't always mean lack of progress, the lack of results can sometimes be interesting and still help us learn new things. if we already knew how to detect, and all the properties of WIMPS then why bother building the experiment to begin with? we would have nothing new to learn.
Finding out what properties WIMPS dont have helps refine our current theories. Some of those theories may have predicted we would see some of those properties, but because experimentation rules it out we now know those are dead ends and so can focus our time on other theories. Lack of results allows us to adjust and focus our experiment in ways that are more likely to receive positive results.
I googled various interaction probabilities, which are expressed in units called barns:
http://www.physics.purdue.edu/...
neutron hitting uranium nucleus: 1 barn
helium nucleus hitting gold nucleus: 100 barns (Rutherford experiment 1911)
anti-neutrino captured by proton making a neutron: 10E-17 barns (first detected 1956)
WIMP hitting a xenon nucleus: 10E-21 barns? (year???) need to 10,000 times better than neutrino detector
Numbers are actually ranges including factors like particle energy and angle.