Image: NOvA
Ron Williams / NOvA
Technicians add modules to the first block of the NOvA detector in Minnesota.
By Senior writer
updated 9/6/2012 8:35:17 PM ET 2012-09-07T00:35:17

Physicists have put the first piece in place for a new detector to study the strange properties of particles called neutrinos.

Neutrinos are all around us, but they rarely collide with other particles, and mostly fly through people, buildings, and the planet Earth as if they weren't there. These chargeless, nearly massless subatomic particles come in three flavors, and can switch between them, changing their identities over and over. Their bizarre properties may help explain some fundamental mysteries of the universe, such as why it's full of matter and not antimatter.

To study neutrinos, scientists must find them. Toward this end, a new experiment is under construction called NOvA (NuMI Off-Axis Neutrino Appearance). The project involves two facilities — one in Ash River, Minn., and the other at the Fermi National Accelerator Laboratory near Chicago — that will send neutrinos back and forth.

Neutrinos will easily pass through the 500 miles (800 kilometers) of earth separating the two bases in less than three milliseconds. Once the neutrinos arrive, physicists are hoping they'll crash into some of the atoms in specially designed detectors filled with a liquid scintillator material. When they do, the bang-up will give off light in the form of photons that can be measured, proving a record of each neutrino encounter. [Strange Quarks and Muons: Nature's Tiniest Particles Dissected (Infographic)]

On Thursday, technicians began to position the first block of this detector at the Ash River site.

"This is a significant step toward a greater understanding of neutrinos," Marvin Marshak, NOvA laboratory director and director of undergraduate research at the University of Minnesota, said in a statement. "It represents many months of hard work on the part of the whole NOvA collaboration."

The detector will comprise 28 blocks in total, each of which weighs 417,000 pounds (189,000 kilograms) and measures 51 by 51 by 7 feet (16 by 16 by 2 meters). Each block will be painstakingly placed inside a 300-foot-long (90-meter-long) detector hall.

The blocks will be empty when installed, and filled with their scintillator liquid once in place.

"About a dozen scientists, engineers and technicians from Fermilab and Argonne have been up to Ash River multiple times in the past year to make this thing happen," said Rick Tesarek, Fermilab physicist and NOvA deputy project leader. "They're part of a team of over a hundred collaborators who have been actively working on the experiment."

Once NOvA is up and running, it will be the most advanced neutrino experiment in North America, scientists say. It is scheduled to begin taking data in 2013.

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The machine will focus on unraveling the puzzle of neutrino flavors. Neutrinos come in three types — electron, muon and tau — which are each associated with the elementary particles bearing those names. Neutrinos transform between these flavors at different rates, and the antimatter partner particles of each of these neutrinos change flavors at different rates still.

Physicists think this discrepancy between the behavior of matter neutrinos and antimatter neutrinos may explain the imbalance between matter and antimatter left over after the big bang started the universe.

But to puzzle this out, scientists need more measurements to pin down the frequency of such transformations.

"Everyone's been watching to see which experiment will make the next big step in uncovering the properties of neutrinos," said Mark Messier, Indiana University physicist and co-spokesperson of the NOvA experiment. "The NOvA experiment should be it. It is uniquely positioned to be the first experiment to determine the ordering of the masses of the three neutrinos."

Follow Clara Moskowitz on Twitter @ClaraMoskowitz or LiveScience @livescience. We're also on Facebook and Google+.

© 2012 All rights reserved.

Explainer: What’s a hadron? Tour the particle zoo

  • Image: Elementary particles

    The Standard Model of particle physics is one of science's most successful theories, enabling the development of devices ranging from light bulbs, to microwave ovens and television, to quantum computing devices. The Standard Model is also one of the oddest theories, because it lays out a dizzying menagerie of hundreds of subatomic particles. At its heart are 16 types of elementary particles ... plus at least one more mysterious particle that scientists are spending billions of dollars to detect.

    Click on "Next" to get the full rundown.

  • Quarks

    Image: Quarks and gluons
    Berkeley Lab

    Six "flavors" of quarks have been detected: up and down, charm and strange, top and bottom. Quarks are almost always found in different combinations, bound together by gluons (more on those later). Particles built up from quarks and gluons are called hadrons. The Large Hadron Collider is so named because it's a large collider that smashes hadrons together.

    Three-quark combinations fit in the category of baryons. The best-known baryons are the proton (with two up quarks and one down quark) and the neutron (with two down quarks and one up quark).

    Particles that have one quark and one antiquark fit in the category of mesons. For example, the pion, or pi meson, contains an up quark and an anti-down quark.

  • Leptons

    Image: Single electrons in helium
    Brown University

    Six "flavors" of leptons have been detected: The negatively charged electron is the best-known lepton — along with its antimatter counterpart, the positron. This photo shows the path of single electrons passing through liquid helium, in an experiment devised by Brown University researchers.

    The muon is also negatively charged, but it's about 207 times as massive as the electron. ("Who ordered that?" physicist Isidor Rabi reportedly asked.) The negatively charged tau particle is even bigger — 3,477 times as massive as the electron — but it decays into other particles in less than a trillionth of a second.

    Each of those leptons has a neutrino associated with it: the electron neutrino, the muon neutrino and the tau neutrino. Neutrinos interact only weakly with other particles, and they zip through our planet virtually without a trace. Physicists only recently determined that they have mass, but there's still a great deal of mystery surrounding the ghostly particles.

  • Force carriers

    Image: Graviton

    The Standard Model sets aside a category for particles that are associated with force fields. The effect of a field can be viewed as involving an exchange of such force-carrying particles.

    Four elementary force-carrying particles have been detected. The best-known force carrier is the photon — which plays a part in the electromagnetic spectrum, including visible light. The gluon binds quarks together through the strong nuclear force. The weak nuclear force involves the exchange of W and Z bosons. The W boson can carry a positive or a negative charge, while the Z boson is neutral.

    If gravity could be incorporated into the Standard Model, the force-carrying particle would be called the graviton (shown here in an artist's depiction). However, gravitons have not yet been detected, and at least for now, such particles are not accounted for in the Standard Model.

  • Bosons vs. fermions

    Image: Bosons vs. fermions
    Rice Univ. via AIP

    All force-carrying particles are bosons, but not all bosons are force carriers. The difference has to do with a property known as particle spin. Particles with a fractional spin value (for example, electrons, protons and neutrons) are fermions. Two identical fermions cannot occupy the same quantum state. This is a property that keeps electrons from collapsing into a jumble, and thus makes chemical reactions possible.

    All particles with a whole-integer spin value are classified as bosons, and such particles can occupy the same quantum state even if they're identical. The photon is the best-known type of boson.

    Even atoms can be classified as fermions and bosons. This photo shows how atom clouds of lithium-7 (bosons) and lithium-6 (fermions) behave at low temperatures. The bosons collapse into a compact cloud, while the fermions can't squeeze that closely together.

  • The mysterious Higgs

    Image: Higgs as seen by CMS
    Ianna Osborne / CERN / CMS Collection

    The Higgs boson is the only particle predicted by the Standard Model that has not yet been detected. The Higgs is the main quarry for physicists at the Large Hadron Collider. This image is a simulation of the Higgs' signature as it might appear in one of the LHC's detectors.

    The Higgs boson, named after Scottish theorist Peter Higgs, is thought to be associated with a field that endows some particles (such as the weak nuclear force's W and Z bosons) with mass, while leaving the electromagnetic force's photons without mass.

    This Higgs field may have played a role at the very beginnings of the universe: Physicists believe that at the highest energies, the electromagnetic and weak nuclear forces were unified, but something led to "electroweak symmetry breaking" as the infant cosmos cooled. That would be why the electromagnetic force and the weak nuclear force are distinct in the current universe. The Large Hadron Collider could shed new light on this mysterious Higgs mechanism.

  • Why so complicated?

    Image: Particle zoo
    Tim Jones / McDonald Observatory / HETDEX

    Hadrons and leptons? Baryons and mesons? Fermions and bosons? Sometimes it seems as if particle physicists set up these classifications just to keep outsiders totally confused. But for researchers, these occasionally overlapping categories are useful for figuring out how different types of particles interact with each other.

    In a sense, it's as if we've been talking about the game of chess but have gotten only to the point of naming the different pieces on the board: black pieces and white ones, pawns and knights, bishops and rooks, kings and queens. The real meaning of the game comes out when you start studying how the pieces perform and interact.

    To delve into the deeper meaning of the Standard Model, you can visit The Particle Adventure at Lawrence Berkeley National Laboratory, "A Subatomic Venture" at CERN, or Particle Physics UK.


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