Beaming boffins feel the rhythm as neutrinos oscillate over 500 miles

Mystery particles rarely interact with matter

MINOS Experiment image taken by Peter Ginter for Fermilab - The MINOS experiment sends a beam of neutrinos 450 miles straight through the earth from Fermilab to northern Minnesota - no tunnel necessary
The MINOS experiment fires a beam of neutrinos straight through the earth. Pic credit: Peter Ginter at Fermilab

Scientists working on the NOvA experiment have spotted what they say is evidence of oscillating neutrinos for the first time in the lab's particle accelerator.

Since February 2014, boffins have been stashing data and recording interaction of the abundant, yet elusive, subatomic particles as they interacted in the specially-built Fermilab – a 14,000-ton far detector based in Ash River, Minnesota.

“People are ecstatic to see our first observation of neutrino oscillations,” said NOvA spokesbeing Peter Shanahan of the US Department of Energy’s Fermi National Accelerator Lab.

He added: “For all the people who worked over the course of a decade on the designing, building, commissioning and operating this experiment, it’s beyond gratifying.”

The data gathered by the researchers allowed systems to be tested before the beefy detector – which stands at 50 feet tall, 50 feet wide and measures 200 feet long – was fired up in November last year.

Fermilab explained the hard science involved in the experiment:

The neutrino beam generated at Fermilab passes through an underground near detector, which measures the beam’s neutrino composition before it leaves the Fermilab site. The particles then travel more than 500 miles straight through the Earth, no tunnel required, oscillating (or changing types) along the way.

About once per second, Fermilab’s accelerator sends trillions of neutrinos to Minnesota, but the elusive neutrinos interact so rarely that only a few will register at the far detector.

When a neutrino bumps into an atom in the NOvA detector, it releases a signature trail of particles and light depending on which type it is: an electron, muon or tau neutrino.

The beam originating at Fermilab is made almost entirely of one type – muon neutrinos – and scientists can measure how many of those muon neutrinos disappear over their journey and reappear as electron neutrinos.

The test uncovered six muon neutrino to electron neutrino oscillations. However, similar long-distance experiments, such as T2K in Japan, have already witnessed such interactions, Fermilab noted.

But with this work scientists have been seeing near equivalent results in a shorter time frame. Apparently, this "bodes well for the experiment's ambitious goal of measuring neutrino properties that have eluded other experiments so far."

NOvA spokesbeing Mark Messier of Indiana University crowed: “Having a beam of that power running so efficiently gives us a real competitive edge and allows us to gather data quickly.”

Among other things, boffins at the lab hope to discover the mystery behind the three types of neutrinos, which do not carry electric charge. For example, it's not yet known which is the heaviest and which is the lightest. Solving that puzzle would allow the team of international physicists to assess theories about how the particle gets its mass.

In fact, as noted by the Beeb, it's been a big week in the world of neutrinos: from the highest-energy neutrino ever spotted to an upcoming paper that will claim neutrinos have been detected beneath the Earth's crust. ®




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