A NEUTRINO TIMELINE


The following is a short history of neutrinos with the perspective of how the histrical events led to the present understanding of three neutrino flavor oscillations and finite neutrino mass.


1920-1927 Charles Drummond Ellis(along with James Chadwick and colleagues) establishes clearly that the beta decay spectrum is really continous, ending all controversies.

1930 Wolfgang Pauli hypothesizes the existence of neutrinos to account for the beta decay energy conservation crisis.

1932 Chadwick discovers the neutron.

1933 Enrico Fermi writes down the correct theory for beta decay, incorporating the neutrino.

1946 Shoichi Sakata and Takesi Inoue propose the pi-mu scheme with a neutrino to accompany muon. (There is a long story about the confusion of mu for pi etc. They were the first to straighten it out and get the spins right, and write down the correct decay scheme completely: pi -> mu + nu_mu, mu -> e + nu_e + nu_mu, and noticed that both numu and nue are light, and neutral with spin 1/2, and suggested that they might be "different".)

1956 Fred Reines and Clyde Cowan discover (electron anti-) neutrinos using a nuclear reactor.

1957 Neutrinos found to be left handed by Goldhaber, Grodzins and Sunyar.

1957 Bruno Pontecorvo proposes neutrino-antineutrino oscillations analogously to K0-K0bar, leading to what is later called oscillations into sterile states.

1962 Ziro Maki, Masami Nakagawa and Sakata introduce neutrino flavor mixing and flavor oscillations.

1962 Muon neutrinos are discovered by Leon Lederman, Mel Schwartz, Jack Steinberger and colleagues at Brookhaven National Laboratories and it is confirmed that they are different from nues.

1964 John Bahcall and Ray Davis propose feasability of measuring neutrinos from the sun.

1965 The first natural neutrinos are observed by Reines and colleagues in a gold mine in South Africa, and by Goku Menon and colleagues in Kolar Gold fields in India, setting first astrophysical limits.

1968 Ray Davis and colleagues get first radiochemical solar neutrino results using cleaning fluid in the Homestake Mine in North Dakota, leading to the observed deficit known as the "solar neutrino problem".

1976 The tau lepton is discovered by Martin Perl and colleagues at SLAC in Stanford, California. After several years, analysis of tau decay modes leads to the conclusion that tau is accompanied by its own neutrino nutau which is neither nue nor numu.

1976 Designs for a new generation neutrino detectors made at Hawaii workshop, subsequently leading to IMB, HPW and Kamioka detectors .

1980s The IMB, the first massive underground nucleon decay search instrument and neutrino detector is built in a 2000' deep Morton Salt mine near Cleveland, Ohio. The Kamioka experiment is built in a zinc mine in Japan.

1985 The "atmospheric neutrino anomaly" is observed by IMB and Kamiokande.

1986 Kamiokande group makes first directional counting observation solar of solar neutrinos and confirms deficit.

1987 The Kamiokande and IMB experiments detect burst of neutrinos from Supernova 1987A, heralding the birth of neutrino astronomy, and setting many limits on neutrino properties, such as mass.

1988 Lederman, Schwartz and Steinberger awarded the Nobel Prize for the discovery of the muon neutrino.

1989 The LEP accelerator experiments in Switzerland and the SLC at SLAC determine that there are only 3 light neutrino species(electron, muon and tau).

1991-2 SAGE (in Russia) and GALLEX (in Italy) confirm the solar neutrino deficit in radiochemical experiments.

1995 Frederick Reines and Martin Perl get the Nobel Prize for discovery of electron neutrinos (and observation of supernove neutrinos) and the tau lepton, respectively.

1996 Super-Kamiokande, the largest ever detector, begins searching for neutrino interactions on 1 April at the site of the Kamioka experiment, with Japan-US team(led by Yoji Totsuka).

1998 After analyzing more than 500 days of data, the Super-Kamiokande team reports finding oscillations and, thus, mass in muon neutrinos. After several years these results are widely accepted and the paper becomes the top cited experimental particle physics paper ever.

2000 The DONUT Collaboration working at Fermilab announces observation of tau particles produced by tau neutrinos, making the first direct observation of the tau neutrino.

2000 SuperK announces that the oscillating partner to the muon neutrino is not a sterile neutrino, but the tau neutrino.

2001 and 2002 SNO announces observation of neutral currents from solar neutrinos, along with charged currents and elastic scatters, providing convincing evidence that neutrino oscillations are the cause of the solar neutrino problem.

2002 Masatoshi Koshiba and Raymond Davis win Nobel Prize for measuring solar neutrinos(as well as supernova neutrinos).

2002 KamLAND begins operations in January and in November announces detection of a deficit of electron anti-neutrinos from reactors at a mean distance of 175 km in Japan. The results combined with all the earlier solar neutrino results establish the correct parameters for the solar neutrino deficit.

2004 SuperKamiokande and KamLAND present evidence for neutrino disappearance and reappearance, eliminating non-oscillations models.

2005 KamLAND announces first detection of neutrino flux from the earth and makes first measurements of radiogenic heat from earth.


This list was compiled by John Learned and Sandip Pakvasa, 5/98, last updated 7/20/05 by jgl.