Nobel laureate supports India’s pursuit of a neutrino lab

If the India-based Neutrino Observatory (INO) goes ahead despite the challenges, it would be one of India’s biggest fundamental science projects, but Nobel laureate and neutrino researcher Takaaki Kajita is convinced the proposed underground laboratory is still worth fighting for.

Neutrinos are abundant particles that have important implications in understanding the origin of matter in the universe. Around 60 years ago, atmospheric neutrinos were discovered in 1965 in a historic scientific experiment conducted inside the gold mines of Kolar, Karnataka. It was a collaboration between scientists from India, Japan and the UK.

Awakened to the potential of neutrino research, Japan continued to conduct experiments on its soil, or rather beneath it, at the Kamioka Observatory, located underground at Ikenoyama. It was here that Masatoshi Koshiba’s team discovered cosmic neutrinos in the late 1980s. Japan then decided to establish a dedicated neutrino observation facility, Super-Kamiokande, which began operations in 1996. In 2002, Koshiba was awarded the Nobel Prize for his contributions.

Indian scientists were not about to be left behind. Although the original experiment had to be shut down in 1992 when the gold mines at Kolar were closed, plans were already underway to build India’s own observatory. After extensive work, a proposal was put together and in 2011 the Indian government announced its intention to allocate around 135 billion rupees for a neutrino observatory in India, to be located 1.3 km underground in Tamil Nadu. More than a decade later, there has been no progress. Today, INO’s fate remains uncertain.

Meanwhile, within a year of the completion of Super-Kamiokande, Japanese researchers obtained the first evidence of a phenomenon called neutrino oscillations, a discovery that led to another Nobel Prize being awarded (jointly) to Takaaki Kajita, a student of Koshiba, in 2015.

Takaaki Kajita, who has spent his entire career as a researcher in his native Japan, is a living example of the benefits of having a neutrino lab close to home. “The lab is easily accessible, and the detectors are nearby,” he said in an interview with reporters at the 73rd Lindau Nobel Laureate Meeting, which concluded on July 5.

Two of the main reasons against INO are the negative impact on the environment and fears of radiation. INO scientists have repeatedly stated that the observatory will be installed one kilometer underground, so the impact on wildlife and ecosystems will be minimal, but what about radiation? “The experiment will not produce any radioactivity and will not work well in places where there is radiation,” the scientists point out on the INO website. The main purpose of placing the detector underground is to protect it from the natural radiation that hits the Earth’s surface.

Kajita said the Japanese project didn’t face much opposition. “We decided to build the detector in an operating mine, so no additional excavation was needed,” he noted. What’s more, the original experiment was designed to look for a hypothetical phenomenon called proton decay, not neutrinos. “It had nothing to do with radiation at all,” he said.

The biggest stroke of luck for Japanese neutrino scientists was the timing of a supernova observed in February 1987. Supernova 1987A occurred while the Kamiokande II detector was in operation, leading to the discovery of cosmic neutrinos by Koshiba’s team. “It was a big shock. People suddenly knew about neutrinos, and they only had a positive image of them,” said Kajita, who was Koshiba’s doctoral student.

The domestic neutrino observatory is envisaged to give the Indian scientific community, including particle physics students, an opportunity to work in a world-class detector without crossing the border. A young Kajita benefited greatly from this privilege in the 1980s. He recalls the excitement during the construction of the Kamiokande detector. “The first people to see and analyse the data were young postdoctoral researchers involved in the Kamiokande and Super-Kamiokande experiments,” he said.

Today, the Super-Kamiokande facility continues to train a new generation of particle physicists. Some take jobs abroad, but many choose to stay in Japan. After receiving the Nobel Prize in 2015, Kajita himself turned down offers for a new position abroad. “As an experimental physicist, it’s very important to be close to the detector,” he explained.

Aware of the setbacks experienced by his Indian colleagues, Kajita insists that the INO dream is worth saving: “It may be a bit late to start building the detector, but it’s very important that we continue working towards an underground laboratory. There’s a lot of work to be done.” [yet] If not done [in the field of neutrino physics].”

(Nandita Jayaraj is a freelance science writer and co-author of Lab Hopping: A Journey to Find India’s Women in Science.)