The United States should devote about $1 billion to build a neutrino experiment that would make the country a major center for particle physics on the world stage, according to a panel of experts – a plan that would involve building a high-power accelerator that would attract international support and cooperation.
The findings released by the Particle Physics Project Prioritization Panel, or P5 for short, outline a 10-year plan for a two-decade vision that would see an ambitious experiment built at the Fermi National Accelerator Laboratory (Fermilab) in Illinois. The report could profoundly influence how federal dollars are spent in the coming decade.
“We want the U.S. to become the leaders in neutrino science,” said Joe Lykken, a particle theorist at Fermilab and a member of the P5 group. “We’d like to use that to bring the world here in the same way that the world went to CERN [European Organization for Nuclear Research] to discover the Higgs boson.”
The story of the Higgs boson – a decades-long international project based in Europe that cost billions of dollars but ultimately solved a mystery and resulted in a Nobel Prize-winning discovery – shows that such collaborations can become remarkable successes, Lykken said. (The drama of the search for the Higgs boson comes to life in the recent documentary "Particle Fever," which follows the scientists' journey at the Large Hadron Collider.)
That’s why the P5 report advocates for continued U.S. funding on such Higgs research in Europe – along with a few other objectives, including searching for dark matter, understanding dark energy and cosmic inflation, and discovering new particles and physical principles. But the U.S. could make a name for itself by focusing on a flagship experiment in neutrino research, Lykken said.
Neutrinos have received a certain amount of popular recognition in recent years; the IceCube detector in Antarctica recently announced that they had seen neutrinos from beyond the solar system, which could give astrophysicists a whole new way to look at the universe. Three years ago, a neutrino that scientists mistakenly thought had managed to travel faster than the speed of light captured the popular imagination before the error was discovered.
Neutrinos are strange little particles; they have almost no mass and hardly ever interact with matter – billions upon billions pass through your finger each second. There are three types, or flavors, of neutrino, and a neutrino particle can suddenly turn into a completely different flavor. As experimental particle physicist Chang Kee Jung explained in a previous post, this chameleon-like behavior is as weird as your scoop of ice cream instantaneously flipping from chocolate to strawberry.
The neutrino, in fact, could be key to understanding why we exist at all in the first place, Lykken said. That’s because the universe should have started out with equal amounts of matter and anti-matter, which annihilate when they come into contact, leaving nothing behind. And yet, matter fills the universe, while anti-matter is in short supply. Some quirk in the neutrino’s behavior could help explain this cosmic asymmetry, Jung explained earlier.
The neutrino’s strange properties and mysterious relationship with other known particles mean that it’s extremely important to study in depth, in a controlled manner, Lykken said. The proposed billion-dollar-plus Long-Baseline Neutrino Facility would do just that, producing neutrinos by shooting a high-powered beam of particles from Fermilab to a detector roughly 1,300 kilometers away. That detector, a tank holding about 50,000 tons of liquid argon, would be nestled underground in the former Homestake gold mine in South Dakota (where an ambitious dark-matter detector also resides). The experiment would become a hub attracting international collaboration, just as the Higgs experiment does, Lykken said.
Fermilab had begun searching for a scientific path forward since the Tevatron, its iconic high-energy particle accelerator, ceased operations in 2011. The P5 plan to focus on neutrino science provides a strong and practical way forward, Lykken said – though it also demotes some ambitious and worthy science experiments simply because of funding limitations, he added.
“If you had more money you would certainly do them,” Lykken said. “We’ve got to focus on the biggest opportunities.”