India-based Neutrino Observatory

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India-based Neutrino Observatory is a project done in collaboration with multiple institutes within India to understand the working of neutrinos. It is an observatory which will be at Pottipuram in Theni District and is expected to be running from 2020.

On January 5th, 2015, the union cabinet of the government of India chaired by the Prime minister has given the approval for this project. It is worth noting that this project is behind schedule by many years due to environmental concerns, unfounded radiation fears and bureaucratic issues.

The total cost of the project will be approximately Rs. 1500 Crores including pre-project work, underground laboratory, construction work, setting up of Inter -Institutional Centre for High Energy Physics (IICHEP) facility at Madurai and building of the Iron Calorimetry (ICAL) detector.

What are Neutrinos and why do we have to study them?

In 1930, Pauli postulated the existence of neutrinos (“the little neutral one”) to explain the conservation of energy, momentum and angular momentum in beta decay. Too much jargon? Let me simplify it. Let us say particle A decays to particle B. Laws of physics tells us that Energy, momentum and angular momentum should be conserved in any physical process with no external force. But in a particular type of processes called “beta decay”, these rules did not hold. So what can we do? We either throw away the rules calling them rubbish or we circumvent the problem by saying, “No No. The laws holds, just that when A decays, not just B is produced, but also C, another particle that we cannot detect that is taking away this unaccounted energy” Alright, but for this hypothesis to be true, one needs to detect these neutrinos. In 1942, Wang Gangchang was the first to discover neutrinos by the method of Electron capture. Over the years, since its discovery, we have come to know quite a few things about neutrinos but there are still lots remaining to know.

1) Flavors of Neutrinos - In simple world, let us called that all matter around us are composed of particles which comes under one big umbrella called “1st generation particles”. This consists of Up and Down quark (which are the constituents of proton and neutron) and electron. The second generation of particle are very similar to the first except that they are heavier and belong to a higher energy plane. The analogus of electron here is called Muon and the Taun in the third generation. Electron, Muon and Taun all come under the family of “Charged Leptons” and each of them have their corresponding Neutral Leptons and these are the three Flavors (types) of Neutrinos - Electron Neutrino, Muon Neutrino and Taun Neutrino.

2) Neutrino Oscillation - There was once a famous problem called Solar neutrino problem. In simple words, with the way we understand the working of the Sun, we expected the earth to receive a certain flux of electron neutrinos. But when we measured the flux, there was a large deficit. Various hypothesis was made to resolve this problem and one such was “Neutrino Oscillations”. It says that when neutrinos are “created” at the source, it may have a specific flavor say, electron neutrino, but as it travels and is detected at the other end, it has a non-zero probability that it can be on another flavor say, muon neutrino. This was a wonderful theory and over the years with the help of various experimental set up, this was proven to be right. But this theory came with a baggage, it required that neutrinos have mass, which was till then thought of to have no mass. And the standard model of particle physics (One big equation which explains a lot of phenomenon in the universe) has no place for neutrinos which have mass. So the theory needs to expanded to accommodate this anomaly.

3) Mass hierarchy - So I told you that there are three flavors of neutrino and that they have mass. But I never mentioned anything about their hierarchy. That is which is heavier? The muon neutrino of the Tau Neutrino? We still don’t have answer to this question. One way to find out is by studying the behavior of neutrinos as they cross through matter (Earth). The normal and the inverted hierarchy will have different values of probability of oscillation and the more precise we are able to make the measurement, the more knowledge we would have about this sector.

What is INO trying to answer

INO will be studying the atmospheric neutrinos. It’s main aim is to measure the mixing angles (~ the probability that one flavor of neutrino converts to another) with more accuracy and to demystify the mass hierarchy. For the problem of mass hierarchy, they will be considering two channels of neutrinos - the up-going and the down-going, compare the two and understand the effect of matter.

In the next decade, there are plans to set up various neutrino observatory across the world each with different purpose and their combined result might help in picking the right theory beyond the standard model.

In the end, people should become more aware of what neutrinos are and how important this project is for India and its physicist. All the unwarranted fears about “nuclear waste” need to be clarified as this isn’t a nuclear reactor as most people think of it to be and this has nothing to do with the nuclear deal with the US. It is important that we as people should support Indian scientist in helping put India progress in the field of High Energy Physics.

Sources: INO

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