The Neutrino Trappers – The New York Times

20 Luglio 2018 0 Di luna_rossa

The Neutrino TrappersDeep in a mountain in southern Russia, scientists are tracking one of the universe’s most elusive particles.

Photographs by Maxim Babenko

Text by Dennis Overbye

Just over the border from Georgia, in the Caucasus Mountains of southern Russia, lies a small town called Neytrino. For the last half-century, its main business has been the study of the tiniest insubstantial bit of matter in the universe, an ephemeral fly-by-night subatomic particle called the neutrino.

This is the home of the Baksan Neutrino Observatory, a warren of tunnels and laboratories burrowed two miles into a mountain, sheltered from the outside universe and cosmic rays underneath 12,000 feet of rock. There vats of liquid wait to record the flight of neutrinos from the center of the sun, from exploding stars, atomic reactors and the Big Bang itself, carrying messages through time.

A laboratory in an underground gallery at the Baksan Neutrino Observatory.

In the gallium-germanium telescope laboratory, a worker crunches number. Fish swimming in an aquarium serve both as companions and as an early warning system in case something goes awry with the laboratory’s radioactive materials.

Neutrinos are the ghost riders of the cosmos, mostly impervious to the forces, like electromagnetism, with which other denizens of nature interact. Neutrinos cruise unmolested through rocks, the earth and even our bodies. In the words of a famous poem by John Updike, they “insult the stallion in his stall.”

The most delicate measurements so far indicate that an individual neutrino weighs less than a millionth what an electron weighs. Baksan is not the only place dedicated to their surreal pursuit.

The men and women in these photographs, taken by Maxim Babenko last year, share an underground union with scientists scattered around the world in equally deep places: the Sanford Underground Research Facility in the former Homestake gold mine in Lead, S.D.; the Gran Sasso National Laboratory, beneath the mountain of that name in Italy; the Sudbury Neutrino Observatory in Ontario, Canada; the Super-Kamiokande, deep within Mount Ikeno, Japan; and IceCube, an array of detectors buried in ice at the South Pole.

All of them are trying to listen to quantum whispers about the nature of reality.


Nail Khairnasov, lead engineering technologist of the gallium-germanium telescope, has been running these devices for nearly 30 years. The telescope, built in the late 1980s, contains 60 tons of gallium.

Valery Gorbachev, a senior researcher, setting up counters with radioactive isotopes of germanium. Each counter contains just a few dozen germanium atoms.

Vintage computers keep track of events observed in the observatory.

One of Baksan’s biggest claims to fame to date was to catch neutrinos emitted by thermonuclear reactions in the center of the sun in nearly 60 tons of liquid gallium. The experiment, called S.A.G.E., for Soviet-American Gallium Experiment, proved that scientists actually do know what powers our favorite star, source of our life and light.

Since the fall of the Soviet Union, the scientists in Baksan have had to fend off both thieves and the Russian government to keep their gallium, an element that goes for some $500 a kilogram.


Musabi Boliev runs the underground scintillation telescope in the observatory, an enormous structure built in 1977 that detects passing neutrinos and measures their energy and direction.

A bust of Lenin and a poster reading “Glory to Soviet Science” are vestiges of the observatory’s origins.

Trolleys convey workers to and from the surface and to spaces within the underground observatory. More than 250 people work at Baksan, 30 of them scientists.

Physicists know that neutrinos come in at least three flavors, known as electron, muon and tau neutrinos, depending on their subatomic origin. To add to the confusion, neutrinos have a kind of quantum superpower: They can molt from one type to another, sort of like a jail escapee changing clothes as he flees. An electron neutrino, say, can emerge from a nuclear reactor in one place and appear in a detector somewhere else as a muon neutrino. This complicates the cosmic accounting of these creatures.

Physicists are arguing intensely these days over whether there is evidence for a fourth type, called sterile neutrinos. That is the object of a new experiment called B.E.S.T., for Baksan Experiment on Sterile Transitions, now underway in the rusty Baksan tunnels.


Above ground, children from the village of Neytrino dream of the World Cup. The local secondary school has about 40 students.

In Elbrus, a village adjacent to Neytrino, children in traditional garb wait for an evening of performance and dancing to begin, a regional pasttime.

Balkar dancing in Elbrus.

Although neutrinos are the lightest and flimsiest and perhaps most fickle particles of the universe, they are also among the most numerous, outnumbering the protons and electrons that make up us and ordinary matter by a billion to one. And so neutrinos contribute about as much mass to the universe as the visible stars.

An extra population of neutrinos discovered by scientists in a cave in the Caucasus would affect basic calculations of the expansion of the universe.


Despite low salaries and a constant hunt for funds, scientists like Dr. Khairnasov quietly carry on the work of understanding the fickle particle.

One of the observatory’s underground trolleys.

A bus conveys Baksan workers — most of whom are mechanics, dispatchers and other support personnel — and others to the nearby town of Tyrnyauz, where many of them live. In the other direction, at the road’s terminus, is a popular ski resort on Mt. Elbrus’s slopes.

The discovery this month of a high-energy neutrino from a far distant galaxy passing through the IceCube detector at the South Pole elicited headlines around the world.

Meanwhile, unaware that they are being harassed by extraterrestrial visitors, horses graze outside Baksan, and life goes on, whether we understand it or not.


Dennis Overbye joined The Times in 1998, and has been a reporter since 2001. He has written two books: “Lonely Hearts of the Cosmos, The Scientific Search for the Secret of the Universe” and “Einstein in Love, A Scientific Romance.” @overbye

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