The questions that plague particle physicists and cosmology buffs seem fundamental, but it's startling how little we really know about some of them; for instance, why does matter exist? Researchers in Japan are undertaking the most sensitive subatomic particle experiment ever ventured in attempt to get to the bottom of that question, shooting neutrinos nearly 300 miles under the mountains, straight through the bedrock under Japan to a detector on the opposite coast, in an attempt to hash out exactly why neutrinos appear to spontaneously change from one kind to another.
Why? According to what we "know" about the universe, there should be roughly the same amount of matter and antimatter in the universe, but since the two destroy each other that would mean the universe should be a massive radioactive mess. Instead, the universe is obviously populated with an abundance of matter; we're not sure why, but physicists speculate that there must be some law of physics operating at the subatomic level that is different for matter and antimatter.
The "T2K" experiment -- short for Tokai-to-Kamioka -- is beaming high-powered streams of neutrinos from a particle accelerator in Tokai village to the Super-Kamiokande detector nearly 300 miles away. Neutrinos don't engage with matter for the most part, but every now and again one smashes into an atomic nucleus in the detector. Researchers at the receiving end can then measure how many muon neutrinos in the beam are changing into electron neutrinos, hoping that observing these oscillations will shed some light on that discrepancy in physical laws.
By comparing what they find out about neutrinos to anti-neutrinos, researchers might be able to figure out why anti-matter has received the short end of the stick in the cosmos, and hence why the universe is -- fortunately for us -- so full of sweet, sweet matter.
I don't understand how this detector holds 50,000 gallons of water when in the photo gallery, another, much smaller neutrino collector held 50,000 gallons of mineral oil.
I would think that it would take a lot more water to fill it up. Online estimates show the average rectangular backyard swimming pool with shallow and deep ends holds between 20&30 thousand gallons. This looks far bigger considering that two men in a raft are dwarfed inside of it. Could you imagine rafting in a swimming pool?
As much as I don't like using wiki, it states 50,000 tons not gallons. The Super-Kamiokande official site also displays 50,000 tons, again not gallons.
So about 12,500,000 gallons of pure water (I think).
Might want to fix that in your captions.
Just a quick thought:
If neutrino detectors work on the principal of looking for that rare instance where a neutrino interacts with the water molecule and produces light, why go through all the trouble of building these massive detectors under ground or in a mountain?
After all, the earth is nearly covered in water, much of it goes deeper than sunlight will penetrate.
Not to mention all the life thats down there. For all we know, the life down there, on some level, is aware of these random sparks of light and has--for some purpose--adapted to them.
I've never dwelled to deep into their science, but I'm sure it has to do with salt/fresh water not being pure in nature. The more impurities/minerals/etc the more things you have to account for in your experiment and it gets unbelievably complicated.
So it has to be in an isolated place, using pure substances like mineral oil or pure water, no(or little) outside interaction.
They do have a neutrino detector in the arctic ice I think. "Antarctic Muon And Neutrino Detector Array"
And they're building another one "Ice Cube."
"it had much less accuracy because of the less controlled conditions and wider spacing of photomultipliers. Super-Kamiokande can look at much greater detail at neutrinos from the Sun and those generated in the Earth's atmosphere; however, at higher energies, the spectrum should include neutrinos dominated by those from sources outside the solar system. Such a new view into the cosmos could give important clues in the search for Dark Matter and other astrophysical phenomena."