TheKolar Gold Fields (KGF), located in theKolar district of the state ofKarnataka,India, are a set of defunctgold mines known for theneutrinoparticle experiments and unusual observations that took place there starting in 1960.[1] The experiments ended with the closing of the mine in 1992.[2]
The initial experiments that took place inKGF were related to the study ofcosmic raymuons.[3] KGF was chosen because the depths of its mines allowed muons to be studied in a better environment than what was possible withmagnetspectrometers operated at sea level. KGF also allowed the scientists to study theenergy spectrum and angular distributions of muons even at very high energies.[3] The mines had abundance ofKolar rock whose special characteristics with respect to density and chemical composition (different from that of normal rock[clarification needed]) were also a useful advantage in the experiments. The first experiments involving variations of muon fluxes (a measurement of muons passing through a given media) with depth was conducted byB. V. Sreekantan[3] in 1950s. These were followed by experiments in 1961 by S. Miyake, V. S. Narasimham, P. V. Ramana Murty (also spelled Ramanamurty in some occasions), the trio sometimes called MNR, and sponsored byTIFR. During 1984, Naba Kumar Mondal, TIFR, and Prof. Ito, Osaka City University, Japan, performed experimental studies onproton decay and indirectly observed the scatter of muons. Murali and Balasubramaniam briefly assisted Mondal and Ito as research assistants.
Neutrino-related experiments were started in KGF in 1964. The main goal was the detection of atmospheric neutrinos, with an understanding that cosmic rays colliding with atmospheric nuclei produce high energypions andmuons, which decay in the Earth's atmosphere to produce billions of neutrinos. The experiments were conducted by groups fromTIFR,Durham University andOsaka University (Bombay-Osaka-Durham collaboration) using basic trigger withscintillation counters andNeon Flash Tubes (NFT) for tracking detectors. Seven detectors were deployed at a depth of 2.3 km in Heathcote shaft andChampion Reefs mines. The experiment, using an ironcalorimeter, discovered the first atmospheric neutrinos about the same time (in 1965) as a similar discovery took place in theEast Rand Proprietary Mines (ERPM experiment) inSouth Africa.[4]The South African experiment begun in 1965, took place 3200 meters underground and was managed by groups fromCase Institute of Technology,University of California, Irvine andUniversity of the Witwatersrand. The effort was led byFrederick Reines and the liquid scintillator detector used was called theCase-Witwatersrand-Irvine orCWI detector.
Although the KGF group detected neutrino candidates two months later than Reines CWI, they were given formal priority for first discovery of atmospheric neutrinos due to publishing their findings two weeks earlier.[5]
Some experimental observations, calledKolar events, have yet to be explained. They suggest the existence of massive (>3 GeV) particles having a long life (10−9 secs). These massive particles are also seen to decay into 2–3 particles.[6] It has been postulated that they could be the result ofneutrino interactions ordark matter decay.[7]
Underground physics laboratories(m of water equiv. shielding) | |
|---|---|
|
12°56′25.6″N78°15′34″E / 12.940444°N 78.25944°E /12.940444; 78.25944
