(IGP) IAS Pre: GS - General Science - Neutrinos

General Science
Neutrinos

NEUTRINOS are teeny, tiny, nearly massless particles that travel at near lightspeeds. Born from violent astrophysical events like exploding stars and gamma ray bursts, they are fantastically abundant in the universe, and can move as easily through lead as we move through air. But they are notoriously difficult to pin down.

"Neutrinos are really pretty strange particles when you get down to it," says John Conway, a professor of physics at University of California, Davis. "They're almost nothing at all, because they have almost no mass and no electric charge...They're just little whisps of almost nothing." Ghost particles, they're often called.

But they are one of the universe's essential ingredients, and they've played a role in helping scientists understand some of the most fundamental questions in physics.

For example, if you hold your hand toward the sunlight for one second, about a billion neutrinos from the sun will pass through it, says Dan Hooper, a scientist at Fermi National Accelerator Laboratory and an associate professor of astronomy and astrophysics at the University of Chicago. This is because they're shot out as a byproduct of nuclear fusion from the sun - that's the same process that produces sunlight.

"They're important to our understanding of the kind of processes that go on in the sun, and also an important building block for the blueprint of nature," Hooper said.

Particle physicists originally believed that neutrinos were massless. But in the 1990s, a team of Japanese scientists discovered that they actually have a smidgen of mass. This tiny bit of mass may explain why the universe is made up of matter, not antimatter. Early in the process of the Big Bang, there were equal amounts of matter and antimatter, according to Conway. "But as the universe expanded and cooled, matter and antimatter were mostly annihilated. And a slight symmetry favored matter over antimatter. We think neutrinos may have something to do with that process.... And it's a puzzle, why we're made out of matter and not antimatter."

Studying neutrinos is difficult. They're tough to detect since they interact so weakly with other particles. But the newly-completed IceCube Neutrino Observatory will study neutrinos inside a cubic kilometer block of ice in Antarctica. Here's how: when the neutrinos interact with atoms inside the deep arctic ice detectors, they sometimes give off puffs of energy.

"As neutrinos pass through and interact, they produce charged particles, and the charged particles traveling through the ice give off light," Conway said. "That's how they're detected. t's like having a telescope for neutrinos underground."

Fermilab National Laboratory has an experiment that hurls a beam of neutrinos 400 miles underground from Wisconsin to Northern Minnesota in about two milliseconds, and the lab is also planning a massive linear accelerator called Project X that will study the subatomic particles by sending them even farther.

"If 100 years ago, I told someone that the universe was filled with massless, chargeless particles with no energy, I wonder if they'd have believed you," Conway said. "Who knows where we'll be 100 years from now."

INDIA-BASED NEUTRINO OBSERVATORY

(INO) is a proposed particle physicsresearch project to primarily study atmospheric neutrinos in a 1,300 meters (4,300 ft) deep cave under Ino Peak near Pudukkottai, Tamil Nadu, India. This project is notable in that it is anticipated to provide a precise measurement of neutrino mixing parameters. The project is amulti-institute collaboration and one of the biggest experimental particle physics projects undertaken in India.

The project, expected to be completed in 2015 at an estimated cost of $250 million, has been cleared by the Ministry of Environment (India) for construction in the Bodi West Hills Reserved Forest in the Theni district of Tamil Nadu. When completed, the INO will house the world's most massive magnet, four times larger than the 12,500-tonne magnet in the Compact Muon Solenoid detector at CERN in Geneva, Switzerland.

History

The possibility of a neutrino observatory located in India was discussed as early as 1989 during several meetings held that year. Since then this question comes up, off and on, in many discussions. The issue was raised again in the first meeting of the Neutrino physics and Cosmology working group during the Workshop on High Energy Physics Phenomenology (WHEPP-6) held at Chennai in January 2000 and it was decided then to collate concrete ideas for a neutrino detector.

Further discussions took place in August 2000 during a meeting on Neutrino Physics at the Saha Institute of Nuclear Physics, Kolkata, when a small group of neutrino physics enthusiasts started discussing the possibilities. The Neutrino 2001 meeting was held in the Institute of Mathematical Sciences, Chennai during February 2001 with the explicit objective of bringing the experimentalists and theorists in this field together. The INO collaboration was formed during this meeting. The firstformal meeting of the collaboration was held in the Tata Institute of Fundamental Research, Mumbai, during September 6 and 7th, 2001 at which various subgroups were formed for studying the detector options and electronics, physics goals and simulations, and site survey.

In 2002, a document was presented to the Department of Atomic Energy, (DAE) which laid out an ambitious goal of establishing an India-based Neutrino Observatory, outlining the physics goals, possible choices for the detector and their physics. Since then many new and fast paceddevelopments have taken place in neutrino physics. The award of the Nobel Prize in Physics (2002) to the pioneers in neutrino physics is a measure of the importance of this field.

As a result of the support received from various research institutes, universities, the scientific community and the funding agency, the Department of Atomic Energy, a Neutrino Collaboration Group (NCG) was established to study the possibility of building an India-based Neutrino Observatory (INO). The collaboration was assigned the task of doing the feasibility studies for which funds were made available by the DAE. A memorandum of understanding (MoU) was signed by the directors of the participating institutes on August 30, 2002 to enable a smooth functioning of the NCG during the feasibility period. The NCG has the goal of creating an underground neutrino laboratory with the long term goal of conducting decisive experiments in neutrino physics as also other experiments which require such a unique underground facility.On November 20, 2009, Ministry of Environment (India) Minister Jairam Ramesh in a letter to Anil Kakodkar, Secretary, Department of Atomic Energy and Chairman, Atomic Energy Commission of India, denied permission for the Department of Atomic Energy to set up the India- ased Neutrino Observatory (INO) project at Singara in Nilgiris, as it falls in the buffer zone of the Mudumalai Tiger Reserve (MTR). Jairam Ramesh said that based on the report of Rajesh Gopal, AdditionalPrincipal Chief Conservator of Forests (PCCF) and Member-Secretary of the National Tiger Conservation Authority (MS-NTCA), the Ministry cannot approve the Singara site. The report says:

"The proposed project site falls in the buffer zone of Mudumalai Tiger Reserve and is in close proximity to the core/critical tiger habitats of Bandipur and Mudumalai Tiger reserves. It is also an elephant corridor, facilitating elephant movement from the Western Ghats to the EasternGhats and vice-versa. The area is already disturbed on account of severe biotic pressure due to human settlements and resorts and that the construction phase of the project would involve transport of building materials through the highways passing through the core area of the Bandipur and Mudmulai Tiger Reserves.

Instead, he suggested an alternate site near Suruli Falls, Theni District in Tamil Nadu. The Minister said this site did not pose the same problems that Singara posed and environmental and forest clearances should not be a serious issue. He also assured the DAE that the Ministry would facilitate necessary approvals for the alternative location. Dr. Naba K. Mondal of the Tata Institute of Fundamental Research, who is the spokesperson for the INO project said:

"But Suruliyar too is in a reserved forest area that is dense and would require cutting down of trees, something that was not required at Singara. Can the government assure us that forest clearance for this site will be given," he asks. "Alternatively, we can move to the nearby Thevaram, which is about 20-30 km away from the Suruliyar falls. This forest area has only shrubs but there is no source of water here and water will have to be piped over a distance of 30 km,"On 18 October 2010, the Ministry of Environment & Forests approved both environment and forest clearance for setting up the observatory in the Bodi West Hills Reserved Forest in the Theni district of Tamil Nadu. The project is expected to be completed in 2015 at an estimated cost of $250 million.

Participating Institutes

Memorandum of Understanding (MoU) spelling out the operational aspects of the project and the mode of utilisation of available funds was signed by seven primary project partners: Tata Institute of Fundamental Research (TIFR), Mumbai,Bhabha Atomic Research Centre (BARC), Mumbai, Institute of Mathematical Sciences (IMSc), Chennai, Saha Institute of Nuclear Physics (SINP), Kolkata, Variable Energy Cyclotron Centre (VECC), Kolkata, Harish Chandra Research Institute HRI), Allahabad and Institute of Physics (IOP), Bhubaneswar.

Thirteen other project participants include: Aligarh University, Aligarh, Banaras Hindu University, Varanasi, Calcutta University (CU), Kolkata, Delhi University (DU), Delhi, University of Hawaii (UHW), Hawaii, Himachal Pradesh University(HPU), Shimla, Indian Institute of Technology, Bombay (IITB), Mumbai, Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, North Bengal University (NBU), Siliguri, Panjab University (PU), Chandigarh, Physical Research Laboratory(PRL), Ahmedabad, Sálim Ali Centre for Ornithology and Natural History (SACON), Tamil Nadu and Sikkim Manipal Institute of Technology, Sikkim.

Design

The primary research instrument will consist of a 50,000 ton magnetized ironparticle physics calorimeter with glass Resistive Plate Chamber (RPC) technology as the sensor elements.

The INO design is mostly based on the monolith experiment that could not go beyond the proposal Stage. The detector was expected to start collecting data in the year 2012. The location of INO has attracted a lot of attention from the neutrino physics community as the distance between INO and CERN is very close to "Magic Baseline" - a distance at which the effect of the CP phase on the measurement of θ13 is minimal.[8] The project has been hit by lack of skilled man power and opposition by environmentalists. In 2008, INO started a graduate training program leading to Ph.D. Degree in High Energy Physics and Astronomy to deal with the shortage of particle physicists.

The Primary goals of the INO are the following

  1. Unambiguous and more precise determination of Neutrino oscillationparameters using atmospheric neutrinos.

  2. Study of matter effects through electric charge identification, that may lead to the determination of the unknown sign of one of the mass differences.

  3. Study of charge-conjugation and charge parity (CP) violation in the leptonic sector as well as possible charge-conjugation, parity, time-reversal (CPT) violation studies.

  4. Study of Kolar events, possible identification of very-high energy neutrinos and multimuon events.

The INO detector consists of 6 centimeters (2.4 in) thick Iron plates as passive material, with RPCs in between as active material. A prototype of the INO detector with 14 layers, measuring 1m x 1m x 1m is already operational in the VECC, Kolkata. The 35 ton prototype is set up over ground to track cosmic muons.

Location

The location of the site was supposed to be Singara 11°32′N 76°36′E 5.5 kilometers (3.4 mi) southwest of Masinagudi in the Nilgiri Hills of South India. The site has been changed due to protests from environmental groups. The INO will now be built at 9°57′14.299″N 77°16′47.561″E Bodi West Hills in Theni district, southern India.

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