Physics Nobel rewards neutrino work, but has sting in the tail for India

As neutrino astronomy comes of age, the Nobel Foundation has decided to award Takaaki Kajita and Arthur B. McDonald with the physics prize for 2015 for their discovery of neutrino oscillations – a property which indicates that the fundamental particle has mass.

Takaaki Kajita is affiliated with the Super-Kamiokande neutrino detector in Japan. He and Yoji Totsuka used the detector to report in 1998 that neutrinos produced when cosmic rays struck Earth’s atmosphere were ‘disappearing’ as they travelled to the detector. Then, in 2002, McDonald of the Sudbury Neutrino Observatory in Canada reported that incoming electron neutrinos from the Sun were metamorphosing into muon- or tau-neutrinos. Electron-neutrino, muon-neutrino and tau-neutrino are three kinds of neutrinos (named for particles they are associated with: electrons, muons and taus).

What McDonald, Kajita and Totsuka had together found was that neutrinos were changing from one kind to another as they travelled – a property called neutrino oscillations – which is definite proof that the particles have mass. Sadly, Totsuka died in 2009, and may not have been considered for the Nobel Prize for that reason.

This was an important discovery for astroparticle physics. For one, the Standard Model group of equations that defines the behaviour of fundamental particles hadn’t anticipated it. For another, the discovery also made neutrinos a viable candidate for dark matter, which we’re yet to discover, and for what their having mass implies about the explosive deaths of stars – a process that spews copious amounts of neutrinos.

Neutrino oscillations were first predicted by the Italian nuclear physicist Bruno Pontecorvo in 1957. In fact, Pontecorvo has laid the foundation of a lot of concepts in neutrino physics whose development has won other physicists the Nobel Prize (in 1988, 1995 and 2002), though he’s never won the prize himself.

An infographic showing how the Super-Kamiokande neutrino experiment works. Source: nobelprize.org
An infographic showing how the Super-Kamiokande neutrino experiment works. Source: nobelprize.org

Although it was a tremendous discovery that neutrinos have mass, a discovery that forced an entrenched theory of physics to change itself, the questions that Pontecorvo, Kajita, McDonald and others asked have yet to be fully answered: one of the biggest unsolved problems in physics today is what the neutrino-mass hierarchy is. In other words, physicists haven’t yet been able to find out – via theory or experiment – which of the three kinds neutrinos is the heaviest and which the lightest. The implications of the mass-ordering are important for physicists to understand certain fundamental predictions of the Standard Model. As it turns out, the model has many unanswered questions, and some physicists hope that a part of the answer may lie in the unexpected properties of neutrinos.

An infographic showing how the Sudbury Neutrino Observatory works. Source: nobelprize.org
An infographic showing how the Sudbury Neutrino Observatory works. Source: nobelprize.org

Exacerbating the scientific frustration is the fact that neutrinos are notoriously hard to detect because they rarely interact with matter. For example, the IceCUBE neutrino observatory operated by the University of Wisconsin-Madison near the South Pole in Antarctica employs thousands of sensors buried under the ice. When a neutrino strikes a water molecule in the ice, the reaction produces a charged lepton – electron, muon or tau, depending on the neutrino. That lepton moves faster through the surrounding ice than the speed of light in ice, releasing energy called Cherenkov radiation that’s then detected by the sensors. Building on similarly advanced principles of detection, India and China are also constructing neutrino detectors.

At least, India is supposed to be. China on the other hand has been labouring away for about a year now in building the Jiangmen Underground Neutrino Observatory (JUNO). India’s efforts with the India-based Neutrino Observatory (INO) in Theni, Tamil Nadu have, on the other hand, ground to a halt. The working principles behind both INO and JUNO are targeted at answering the mass-ordering questions. And if answered, it would almost definitely warrant a Nobel Prize in the future.

INO’s construction has been delayed because of a combination of festering reasons with no end in sight. The observatory’s detector is a 50,000-ton instrument called the iron calorimeter that is to be buried underneath a kilometre of rock so as to filter all particles but neutrinos out. To acquire such a natural shield, the principal institutions involved in its construction – the Department of Atomic Energy (DAE) and the Institute of Mathematical Sciences, Chennai (Matscience) – have planned to hollow out a hill and situate the INO in the resulting ‘cave’. But despite clearances acquired from various pollution control boards as well as from the people living in the area, the collaboration has faced repeated resistance from environmental activists as well as politicians who, members of the collaboration allege, are only involved for securing political mileage.

Schematic view of the Underground neutrino lab under a mountain. Credit: ino.tifr.res.in
Schematic view of the Underground neutrino lab under a mountain. Credit: ino.tifr.res.in

The DAE, which obtained approval for the project from the Cabinet and the funds to build the observatory, has also been taking a hands-off approach and has until now not participated in resolving the face-off between the scientists and the activists.

At the moment, the construction has been halted by a stay issued by the Madurai Bench of the Madras High Court following a petition filed with the support of Vaiko, founder of the Marugmalarchi Dravida Munnetra Kazhagam. But irrespective of which way the court’s decision goes, members of the collaboration at Matscience say that arguments with certain activists have degenerated of late, eroding their collective spirit to persevere with the observatory – even as environmentalists continue to remain suspicious of the DAE. This is quite an unfortunate situation for a country whose association with neutrinos dates back to the 1960s.

At that time, a neutrino observatory located at a mine in the Kolar Gold Fields was among the first in the world to detect muon neutrinos in Earth’s atmosphere – the same particles whose disappearance Takaaki Kajita was able to record to secure his Nobel Prize for. Incidentally, a Japanese physicist named Masatoshi Koshiba was spurred by the KGF discovery to build a larger neutrino detector in his country, called Kamioka-NDE, later colloquialised to Kamiokande (Koshiba won the Nobel Prize in 2002 for discovering the opportunities of neutrino astronomy). Kamiokande was later succeeded by Super-Kamiokande, which in the late-1990s became the site of Kajita’s discovery. The KGF observatory, on the other hand, was shut in the 1992 as the mines were closed.

For the broader physics community, brakes applied on the INO’s progress count for little because there are other neutrino detectors around the world – like JUNO – as well as research labs that can continue to look for answers to the mass-ordering question. In fact, the Nobel Prize awarded to Kajita and McDonald stands testimony to the growing realisation that, like the particles of light, neutrinos can also be used to reveal the secrets of the cosmos. However, for the Indian community, which has its share of talented theoretical physicists, the slowdown signifies a slipping opportunity to get back in the game.

The Wire
October 6, 2015

Construction has started on two of the world's grandest neutrino observatories

The groundbreaking ceremony for the Jiangmen Underground Neutrino Observatory happened on January 10. This means construction on Asia’s two biggest neutrino experiments will have started in the span of a week, after the India-based Neutrino Observatory was given the go-ahead by the government on January 5.

Where the INO uses a device called the iron calorimeter to ‘trap’ and study neutrinos, the JUNO will use a liquid scintillator neutrino detector: a large container filled with a pristine liquid and lined with sensors. LSNDs are used to count the number of a neutrinos emerging from particular sources, which in JUNO’s case will be two nuclear power plants (comprising 10 reactors with an output of 35.8 GW) situated 53 km from the observatory.

JUNO will also be China’s second big neutrino experiment. The first is the Daya Bay Reactor experiment, which – also using an LSND – studies neutrinos produced by cosmic muons. In 2012, it announced an important result concerning the mass hierarchy of the three types of neutrinos, placing the JUNO in good stead on two fronts, so to speak: with designing and operating an LSND and with using such an installation to get results. Thus, the Institute of High Energy Physics responsible for JUNO already has over 300 scientists from 45 institutions in nine countries working with it.

India, on the other hand, has little to count on on that front, which is why the INO is still soliciting collaborators despite showing no signs of any flaws in its design or effective implementation. The lack of experience also shows in a more subtle, but no less telling, way: in the press releases crafted by the respective organisations. While the TIFR/IMSc statement issued for the INO stuck to the point, the IHEP statement for JUNO expressed confidence about getting results, too.

Both INO and JUNO, once simultaneously operational in 2020, will be extending the study of the neutrino mass hierarchy problem on a grand scale. At the INO calorimeter’s heart will sit the world’s most massive electromagnet while the JUNO’s LSND will comprise the world’s most voluminous LSND tank. At the same time, the two observatories don’t signify the dawn of experimental neutrino physics in Asia; the Kolar Gold Fields neutrino experiment in India took care of that in 1964.

Construction has started on two of the world’s grandest neutrino observatories

The groundbreaking ceremony for the Jiangmen Underground Neutrino Observatory happened on January 10. This means construction on Asia’s two biggest neutrino experiments will have started in the span of a week, after the India-based Neutrino Observatory was given the go-ahead by the government on January 5.

Where the INO uses a device called the iron calorimeter to ‘trap’ and study neutrinos, the JUNO will use a liquid scintillator neutrino detector: a large container filled with a pristine liquid and lined with sensors. LSNDs are used to count the number of a neutrinos emerging from particular sources, which in JUNO’s case will be two nuclear power plants (comprising 10 reactors with an output of 35.8 GW) situated 53 km from the observatory.

JUNO will also be China’s second big neutrino experiment. The first is the Daya Bay Reactor experiment, which – also using an LSND – studies neutrinos produced by cosmic muons. In 2012, it announced an important result concerning the mass hierarchy of the three types of neutrinos, placing the JUNO in good stead on two fronts, so to speak: with designing and operating an LSND and with using such an installation to get results. Thus, the Institute of High Energy Physics responsible for JUNO already has over 300 scientists from 45 institutions in nine countries working with it.

India, on the other hand, has little to count on on that front, which is why the INO is still soliciting collaborators despite showing no signs of any flaws in its design or effective implementation. The lack of experience also shows in a more subtle, but no less telling, way: in the press releases crafted by the respective organisations. While the TIFR/IMSc statement issued for the INO stuck to the point, the IHEP statement for JUNO expressed confidence about getting results, too.

Both INO and JUNO, once simultaneously operational in 2020, will be extending the study of the neutrino mass hierarchy problem on a grand scale. At the INO calorimeter’s heart will sit the world’s most massive electromagnet while the JUNO’s LSND will comprise the world’s most voluminous LSND tank. At the same time, the two observatories don’t signify the dawn of experimental neutrino physics in Asia; the Kolar Gold Fields neutrino experiment in India took care of that in 1964.

Cabinet approves India-based Neutrino Observatory

On Monday, the Prime Minister’s Office gave the go ahead for the India-based Neutrino Observatory, an underground physics experiment that will study particles called atmospheric neutrinos. The project is based out of Theni in Tamil Nadu, and the Tamil Nadu State Government is providing the infrastructural support. The observatory is expected to cost Rs 1,500 crore and to be completed by 2020. With the PMO’s green signal, the consortium of institutions will now receive the bulk of funds with which to start excavating the underground cavern.

The INO is jointly supported by the Department of Atomic Energy and the Department of Science and Technology. The Tata Institute of Fundamental Research, Mumbai, is the host institution. Additionally, an Inter-Institutional Center for High Energy Physics has also been set up in Madurai to lead the R&D for the observatory. The approval confirmation came from Prof. Naba K Mondal of the TIFR and spokesperson for the project.

Upon completion, the INO is being envisaged as the return to India of world-class experimental neutrino physics. From the 1960s until the 1990s, a neutrino experiment at the Kolar Gold Field Mines held that bragging right. In the years since the mines were closed, however, it became evident that the experiment they’d housed could have made some important contributions to understanding the masses of the three types of neutrinos, an important question today.

The PMO’s go-ahead also includes the approval to construct a 50,000-ton electromagnet – the world’s largest upon completion – that will be the heart of the stationary Iron Calorimeter detector. It will comprise “alternate layers of particle detectors called Resistive Plate Chambers (RPCs) and iron plates. The iron plates will be magnetized with 1.4 Tesla magnetic field. Over 30,000 RPCs will be used in this detector. A total of over 3.7 million channels of electronics will carry the signals from these RPCs to be finally stored in the computer,” according to the press release accompanying the announcement.

Some members of the INO at the site of the project, in the Bodi West Hills. Prof. Mondal is second from left.
Some members of the INO at the site of the project, in the Bodi West Hills. Prof. Mondal is second from left. Credit: http://www.ino.tifr.res.in/ino/

Because neutrinos interact so rarely with matter, an experiment to study them must disallow particulate interactions of any other kind in its kind. This is why the INO will be situated beneath 2.2 km of rock acting as a shield.

A similar neutrino experiment is simultaneously coming up in China, called the Jiangmen Underground Neutrino Observatory. JUNO has two important similarities with INO: both will attempt to answer questions surrounding the subject of neutrino masses and both expect to start operating by 2020. The supplementarity means the experiments could corroborate each others’ results. The complementarity means it will be a challenge for each experiment to produce unique results, although it is too early to say how important such a consideration is now.

At the same time, JUNO has an important edge: It is already an international collaboration of participating institutions while India is still soliciting partnerships.

Finally, because of its scale and the level of funding it will receive, the INO will eventually house a full-fledged scientific institution of sorts, with research in the other sciences as well. Even as an underground neutrino experiment, the observatory has potential to host others which might require a similar environment to study: a neutrinoless doube beta decay experiment to study the nature of neutrinos and a dark-matter detector, to name two.

As Sekhar Basu, the Director of BARC, noted: “Development of detector technologies for various particle physics experiments and their varied applications including societal applications in areas like medical imaging is an important aspect of the project.” Not to forget the development of highly skilled technical manpower.

The full list of the INO-ICAL collaborators is available on the last page of the press release (which I’ve uploaded to Scribd). Thanks to Prof. Mondal for informing us about the development. Good luck, INO team!

 

An elusive detector for an elusive particle

The delay of a go-ahead from the Cabinet for an indigenously designed neutrino detector is demoralizing for scientists because it could turn investors away.

(This article originally appeared in The Hindu on March 31, 2014.)

In the late 1990s, a group of Indian physicists pitched the idea of building a neutrino observatory in the country. The product of that vision is the India-based Neutrino Observatory (INO) slated to come up near Theni district in Tamil Nadu, by 2020. According to the 12th Five Year Plan report released in October 2011, it will be built at a cost of Rs.1,323.77 crore, borne by the Departments of Atomic Energy (DAE) and Science & Technology (DST).

By 2012, these government agencies, with the help of 26 participating institutions, were able to obtain environmental clearance, and approvals from the Planning Commission and the Atomic Energy Commission. Any substantial flow of capital will happen only with Cabinet approval, which has still not been given after more than a year.

If this delay persists, the Indian scientific community will face greater difficulty in securing future projects involving foreign collaborators because we can’t deliver on time. Worse still, bright Indian minds that have ideas to test will prioritise foreign research labs over local facilities.

‘Big science’ is international

This month, the delay acquired greater urgency. On March 24, the Institute of High Energy Physics, Beijing, announced that it was starting construction on China’s second major neutrino research laboratory — the Jiangmen Underground Neutrino Observatory (JUNO), to be completed at a cost of $350 million (Rs. 2,100 crore) by 2020.

Apart from the dates of completion, what Indian physicists find more troubling is that, once ready, both INO and JUNO will pursue a common goal in fundamental physics. Should China face fewer roadblocks than India does, our neighbour could even beat us to some seminal discovery. This is not a jingoistic concern for a number of reasons.

All “big science” conducted today is international in nature. The world’s largest scientific experiments involve participants from scores of institutions around the world and hundreds of scientists and engineers. In this paradigm, it is important for countries to demonstrate to potential investors that they’re capable of delivering good results on time and sustainably. The same paradigm also allows investing institutions to choose whom to support.

India is a country with prior experience in experimental neutrino physics. Neutrinos are extremely elusive fundamental particles whose many unmeasured properties hold clues about why the universe is the way it is.

In the 1960s, a neutrino observatory located at the Kolar Gold Fields in Karnataka became one of the world’s first experiments to observe neutrinos in the Earth’s atmosphere, produced as a by-product of cosmic rays colliding with its upper strata. However, the laboratory was shut in the 1990s because the mines were being closed.

However, Japanese physicist Masatoshi Koshiba and collaborators built on this observation with a larger neutrino detector in Japan, and went on to make a discovery that (jointly) won him the Nobel Prize for Physics in 2002. If Indian physicists had been able to keep the Kolar mines open, by now we could have been on par with Japan, which hosts the world-renowned Super-Kamiokande neutrino observatory involving more than 900 engineers.

Importance of time, credibility

In 1998, physicists from the Institute of Mathematical Sciences (IMSc), Chennai, were examining a mathematical parameter of neutrinos called theta-13. As far as we know, neutrinos come in three types, and spontaneously switch from one type to another (Koshiba’s discovery).

The frequency with which they engage in this process is influenced by their masses and sources, and theta-13 is an angle that determines the nature of this connection. The IMSc team calculated that it could at most measure 12°. In 2012, the Daya Bay neutrino experiment in China found that it was 8-9°, reaffirming the IMSc results and drawing attention from physicists because the value is particularly high. In fact, INO will leverage this “largeness” to investigate the masses of the three types of neutrinos relative to each other.

So, while the Indian scientific community is ready to work with an indigenously designed detector, the delay of a go-ahead from the Cabinet becomes demoralising because we automatically lose time and access to resources from potential investors.

“This is why we’re calling it an India-based observatory, not an Indian observatory, because we seek foreign collaborators in terms of investment and expertise,” says G. Rajasekaran, former joint director of IMSc, who is involved in the INO project.

On the other hand, China appears to have been both prescient and focussed on its goals. It purchased companies manufacturing the necessary components in the last five years, developed the detector technology in the last 24 months, and was confident enough to announce completion in barely six years. Thanks to its Daya Bay experiment holding it in good stead, JUNO is poised to be an international collaboration, too. Institutions from France, Germany, Italy, the U.S. and Russia have evinced interest in it.

Beyond money, there is also a question of credibility. Once Cabinet approval for INO comes through, it is estimated that digging the vast underground cavern to contain the principal neutrino detector will take five years, and the assembly of components, another year more. We ought to start now to be ready in 2020.

Because neutrinos are such elusive particles, any experiments on them will yield correspondingly “unsure” results that will necessitate corroboration by other experiments. In this context, JUNO and INO could complement each other. Similarly, if INO is delayed, JUNO is going to look for confirmation from experiments in Japan, South Korea and the U.S.

It is notable that the INO laboratory’s design permits it to also host a dark-matter decay experiment, in essence accommodating areas of research that are demanding great attention today. But if what can only be called an undue delay on the government’s part continues, we will again miss the bus.