India-based Neutrino Observatory

Neutrinos are probably the strangest of all elementary particles - quick as light, unimaginable numbers of them race through space. They are a neutral, subatomic particle with a mass close to zero and a half-integral spin. They rarely interact with normal matter, which is perhaps why scientists around the world are eager to capture - and analyze - this process.

"We have been part of many collaborations abroad," said the India-based Neutrino Observatory's outreach coordinator, physicist D. Indumathi. "Here, we have a fully Indian experiment where we have the chance to determine our own physics goals and ideas, our own experiments, our equipment."

The INO will be housed in a 1.3 km-long tunnel (three quarters of a mile) that contains three caverns and a 50,000-ton iron calorimeter, which detects changes in heat. That neutrino detector will be the most massive in the world.

Because neutrinos only weakly interact with other particles of matter, neutrino detectors must be very large in order to detect a significant number of neutrinos.

"The technology that we are building indigenously is totally different from all the detectors that are built for neutrinos," says Anil Prabhakar, a professor in electrical engineering. "While a lot of other basic fundamental particles have been studied in large experiments, the neutrino has always been elusive."

A slippery particle

Neutrinos come in three types, or "flavors": electron-neutrino, muon-neutrino and tau-neutrino. They oscillate among the three. Each neutrino flavor has a slightly different mass, although physicists do not yet know exactly what those masses are.

"These neutrinos do a three-level Jekyll and Hyde," says Indumathi. "They keep kind of oscillating into each other. So sometimes you see a neutrino as one type and as it goes along, it oscillates or transforms into another type."

One of the main aims of the experiment is to measure the mass of these neutrinos through these oscillations. The mass differences among flavors are believed to be the main factor affecting how neutrinos oscillate or morph as they pass through space, matter and Earth. Calculations suggest there must be around 40 billion of the "invisible" neutrinos in a cubic centimeter of the atmosphere.

Despite their small size, the neutrino mass has far-reaching inferences - for example, implying that they played a decisive role in the formation of the universe. It potentially blurs the distinction between matter and antimatter, which might account for the apparent absence of antimatter.

"One can address larger questions like matter and anti-matter asymmetry," says M V N Murthy, who is also associated with the project. "In order to understand all these things, neutrino is an important part which may lead to a better understanding of our universe."

Neutrino race?

Most advanced countries are already working vigorously in neutrino science with dedicated labs. These include the United States, Russia, France, Italy, China, Japan and South Korea.

In March this year, China also announced the construction of a neutrino observatory in its Jiangmen province with similar goals. Like the INO, the Jiangmen underground neutrino observatory is expected to be completed by 2020. Work has already begun.

With so many countries studying the properties of neutrino it would almost seem as if there is a race among growing economies

But Indumathi feels differently.

"I think there are neutrino physicists everywhere on earth. Some are underground, some are on the surface of the earth, and some are at the South Pole. I think there is no limit to neutrino physicists in choosing sites," she says.

This project in India involves nearly 26 scientific institutions and about 100 scientists drawn from the country, a collaboration which is expected to grow further in the coming years. Apart from the scientific aims, it is the largest basic sciences project ever considered in India.

The scientific community believes the ambitious project could open up new vistas in the fields of astronomy and astrophysics, communication and even in medical imaging, through the detector spin-offs.

While environmental impact concerns have delayed the project, the scientists involved expect research results within 15 years.