The Kolar Gold Fields (KGF), located in the Kolar district of the state of Karnataka, India, are a set of defunct gold mines known for the neutrino particle experiments and observations that took place there starting in 1960.[1] The experiments ended with the closing of the mine in 1992.[2]

Initial experiments

The initial experiments that took place in KGF were related to the study of cosmic ray muons.[3] KGF was chosen because the depths of its mines allowed muons to be studied in a better environment than what was possible with magnet spectrometers operated at sea level. KGF also allowed the scientists to study the energy spectrum and angular distributions of muons even at very high energies.[3] The mines had abundance of Kolar rock whose special characteristics with respect to density and chemical composition (different from that of normal rock) 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 by Sreekantan[3] in 1950s. These were followed by experiments in 1961 by Miyake, Narasimham and Ramanamurty and sponsored by TIFR. During 1984, Naba Kumar Mondal, TIFR, and Prof. Ito, Osaka City University, Japan, performed experimental studies on proton decay and indirectly observed the scatter of muons. Murali and Balasubramaniam briefly assisted Mondal and Ito as research assistants.
Neutrino find

Neutrino-related experiments were started in KGF in 1964. The main goal was the detection of atmospheric neutrinos, with an understanding that cosmic rays contain high energy pions and muons which decay in the Earth's atmosphere to produce billions of neutrinos. The experiments were conducted by groups from TIFR, Durham University and Osaka University using basic trigger with scintillation counters and Neon Flash Tubes (NFT) for tracking detectors. Seven detectors were deployed at a depth of 2.3 km in Heathcote shaft and Champion Reefs mines. The experiment discovered the first atmospheric neutrinos in an iron calorimeter here about the same time as a similar discovery in the East Rand Proprietary Mines (ERPM experiment) in South Africa[4]. The South African experiment begun in 1965, took place 3200 meters underground and was managed by groups from Case Institute of Technology, University of California, Irvine and University of Witswatersrand.
Kolar events

Some experimental observations, called Kolar 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.[5] It has been postulated that they could be the result of neutrino interactions or dark matter decay.[6]

H. Adarkar; et al. (2000). "Experimental Evidence for G.U.T Proton decay".arXiv:hep-ex/0008074.
N. K. Mondal (2004). "Status of India-based Neutrino Observatory (INO)" (PDF). Proceedings of the Indian National Science Academy. 70 (1): 71–77.
V. S. Narasimhan (2004). "Perspective of Experimental Neutrino Physics in India" (PDF). Proceedings of the Indian National Science Academy. 70 (1): 11–25.
T. K. Gaisser (2005). "Atmospheric Neutrino Fluxes". Physica Scripta. T121: 51–56.arXiv:astro-ph/0502380. Bibcode:2005PhST..121...51G. doi:10.1088/0031-8949/2005/T121/007.
S. L. Glashow; H. van Dam; P. H. Frampton (1982). Third Workshop on Grand Unification, University of North Carolina, Chapel Hill. Birkhäuser Verlag. ISBN 978-3-7643-3105-4.
M. V. N. Murthy; G. Rajasekaran (2014). "Anomalous Kolar events revisited: Dark Matter?". Pramana. 82 (3): 609.arXiv:1305.2715. Bibcode:2014Prama..82..609M. doi:10.1007/s12043-014-0718-5.

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