World's Most Sensitive Neutrino Experiment Launches, To Seek Answers About Matter's Origins

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.

Super-Kamiokande
Built in an abandoned mine, the "Super-K" neutrino detector surrounds 50,000 gallons of super pure water with 11,200 photomultiplier tubes. To give an idea of the scale, that object in the distance is two men in a rubber raft.courtesy of the Science and Technology Facilities Council of the UK
Liquid Scintillator Neutrino Detector
The Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory contained 50,000 gallons of mineral oil, and operated from 1993 to 1998.courtesy of the Department of Energy
Sudbury Neutrino Detector
This detector is 40 feet in diameter and is located 6,800 feet underground. Data from the Sudbury detector helped prove that neutrinos do in fact have mass.courtesy of A. B. McDonald (Queen's University)
Antarctic Impulsive Transient Antenna
To avoid the contaminating signals generated by civilization, this neutrino detector was attached to a weather balloon and floated across Antarctica on a 35 day long flight.courtesy of Kim Paladino (Ohio State)