Neutrino factory could be right prescription to see theta13
|Scientists would use a neutrino factory to smash protons into a target, collect muons resulting from the collision, cool them to similar energies and momenta, accelerate them and let them decay into neutrinos.
Most neutrino experiments running today have one thing in common: They are trying to pin a number on a parameter known as theta13, or θ13.
This number may simply equal zero. But if it doesn't, it might tell physicists something about the role of neutrinos in the imbalance between matter and antimatter in the universe, the reason we exist.
Physicists have put tighter and tighter constraints on the number. A recent result from the MINOS collaboration at Fermilab allowed them to push the limits previously set by the CHOOZ experiment in France. If θ13 is very small, it could take a new type of neutrino experiment to find it: a neutrino factory.
Sixty-four physicists from 30 American and European institutions met at Fermilab in early April as part of an international design study with a goal of creating a design report for a neutrino factory in the next few years. The report will include a recommended design and cost estimate and will open the door for a laboratory to propose to build a neutrino factory.
Neutrinos come in three flavors and in three masses. A neutrino of one mass is actually a mixture of the three flavors. It spends some portion of its time as an electron neutrino, some as a muon neutrino and some as a tau neutrino. Switching from flavor to flavor is called oscillation.
Physicists think that all three masses of neutrinos follow this pattern, each with a different recipe for how much time it spends as each flavor. But they have not observed every possible type of oscillation.
Theta13 is a measure of how often electron neutrinos oscillate into tau neutrinos. If this type of oscillation happens at all, θ13 will be larger than zero. But if θ13 is a very small number, today's neutrino experiments may not have the precision to find it.
"Then the neutrino factory looks interesting," said Fermilab physicist Alan Bross, co-spokesperson for the Neutrino Factory and Muon Collider collaboration.
"It's like a new pair of glasses," said Vladimir Shiltsev, director of Fermilab's Accelerator Physics Center. "So you can read what Mother Nature wrote in her book."
-- Kathryn Grim