Historical plots

We display below some plots or figures that mark the history of Neutrino Physics, either breakthrough and primary results or summary plots corresponding to milestones. This list is non-exhaustive and is the arbitrary choice of the authors.

Color legend: [Red=Reactors neutrinos] [Yellow=Solar or SN neutrinos] [Blue=Atmospheric neutrinos] [Green=Particle accelerators neutrinos] [Grey=Other neutrinos]


First result: Continuous beta spectrum measurement

First beta spectrum measured by James Chadwick in 1914, while he was working in Germany. Figure shows the energy spectrum of the decay of Ra B+C: four lines, identical to some found previously, superposed on a larger continuous spectrum.


First result: Continuous beta spectrum measurement

Beta spectrum measured by Ellis and Wooster. It figures out the number of electrons emitted by a radium beta-radioactive source, as a function of their energy. The curve is an extrapolation from the measurement points.


Scheme of the first neutrino project of F. Reines and C. Cowan

The idea was to detect the neutrinos produced by a nuclear explosion, with an underground detector close to the explosion area. Fortunately this “crazy” idea has not been used. This would have been a dark stain on the history of the neutrino.

The Poltergeist project


First result: Evidence for the neutrino by F. Reines and C. Cowan

Fred Reines and Clyde Cowan performed a first experiment in 1953, close to the Hanford nuclear power plant [Rei53]. The result was not really significant. They improved their apparatus (bigger detector and better shielding against cosmic rays) and did a second experiment in 1956 at the Savannah River nuclear power plant. That led to the unambiguous evidence of neutrinos interactions in the detector [Cow56,Rei56].

[We use the generic term “neutrino”, but, to be exact, nuclear reactors emit anti-electron-neutrinos νe].


First result: Goldhaber experiment showing that neutrinos are left-handed

The helicity of the neutrino is measured by a combined analysis of circular polarization and resonant scattering of gamma-rays following orbital electron capture.

Upper figure shows the scheme of the experiment: the source of 152mEu (0), at the top of the magnet (alternatively magnetized up and down), decays to an excited state of 152Sm with emission of 840 keV neutrinos, followed by a 960 keV gamma-ray. The gamma-rays which pass through the magnet are resonant-scattered from a Sm2O3 scatterer and detected by a NaI scintillator counter.

Lower figure shows the energy of the resonant-scattered gamma-rays. It contains both gamma-rays emitted from the 960 keV state (960 and 840 keV). It is deduced that the gamma-rays are circularly polarized and that their helicity is negative.

[See details in the original paper [Gol58]]


First result: Observation of the muon-neutrinos νμ, a second family of neutrinos.
[Sch60] [Pon59b] [Dan62]

The idea that there could be a second family of neutrinos was proposed independently by Pontecorvo [Pon59b] and Melvin Schwartz [Sch60]. To observe this new family, Schwartz proposed the scheme shown on the left. Difficult to imagine a more simple figure which led to a great discovery and a Nobel prize!

This elegant scheme is at the origin of the spark chamber experiment  set up by Schwartz, Lederman and Steinberger at the Brookhaven laboratory in 1962. Neutrinos come from the decay of pions produced in the proton interactions. About 100 muon-neutrino νμ interactions were observed [Dan62].

Neutrino-nucleon cross section measurement


First result: Measurement of neutrino-nucleon cross-section

Those points are experimental measurements of the cross section (probability of interaction) of νμ on neutrons within nucleus of carbon atoms. They did not show yet significantly the increase of the cross-section with energy but confirmed the very low value predicted by theory (the 3 curves for the 3 different values of the W boson mass which was not yet known in 1971).


First result: Discovery of Neutral Current interactions in the Gargamelle experiment
[Has73a] [Has73b]

The photograph shows the electron coming from the elastic interaction of a muon-antineutrino νμ with an electron in the Gargamelle bubble chamber, at CERN [Has73a]. This is the first evidence for leptonic neutral current interaction.

The discovery of the hadronic neutral current is shown on the lower figure [Has73b]. Discuter avec Didier de ne montrer qu’une partie de la figure 1 du papier.


First result: Homestake solar neutrino experiment and solar neutrino problem.

The radiochemical solar neutrino chlorine experiment was installed by Ray Davis in the Homestake mine in the middle of the 60’s. The principle was the transformation of 37Cl atoms induced by neutrinos νe into radioactive 37Ar atoms. The first results were published in 1968 [Dav68]. They showed for the first time the deficit of observed solar neutrino interactions compared to the predictions of solar models by John Bahcall. In the following years the updated results confirmed the deficit, giving rise to the so-called solar neutrino problem.

From 1976, the results were presented in the form of the well-known “Davis plot” (see figure), which showed the experimental measurements compared to the theoretical predictions.


First results: Detection of neutrinos from SN1987A by Kamiokande and IMB
[Hir87] [Bio87]

The supernova SN1987A has been discovered in the Large Magellanic Cloud by Shelton in Chile (IAU Circular 4316, on February 24, 1987). Immediately, the physicists of the Kamiokande and IMB (Irvine-Michigan-Brookhaven) experiments analyzed their data and identified an excess of events, about 10 events in each experiment in about 10 seconds, on Feb 23, 1987, 07:35:41 UTC. These bursts of neutrino events, in coincidence with the SN1987A optical observation, mark the start of the neutrino astronomy.

The figure shows the time sequence of events observed in Kamiokande.

LEP measurements of the Z width


First result: LEP finds 3 neutrino families

LEP measurements of the Z width provided information about the number of neutrino families. The measurement’s points shown here are average hadronic cross-sections computed from the results of the 4 LEP experiments and showing the resonance corresponding to the Z boson. The colored curves are the theoretical predictions depending on the number of neutrinos types which are active in the weak interaction. The curve with 3 neutrino types best fits the measurements.


Summary: Homestake radiochemical solar neutrino experiment [Cle98].

The pioneer chlorine solar neutrino experiment run in the Homestake mine for 30 years (1968-1998). The figure shows the final result: each point gives the daily rate of radioactive 37Ar atoms produced by solar neutrinos and extracted from the 600 tons of the C2Cl4 solution of the detector. In SNU’s (solar neutrino units), the result is 2.56+-0.16+-0.16 about three times lower than the predictions of solar models (about 8 SNUs).

Gallex and Sage solar neutrino results


Summary:  Detection of pp solar neutrinos with radiochemical gallium experiments (GALLEX and SAGE) [Ans92,Abd94]

The chlorine solar neutrino experiment was not sensitive to the neutrinos coming from the primordial pp fusion reaction in the core of the Sun (which is directly linked to the luminosity of the Sun). In the middle of the 80’s, two experiments used gallium targets (lower threshold than the chlorine) to trap solar neutrinos by the transformation of 71Ga atoms into radioactive 71Ge atoms: GALLEX in the Gran Sasso underground laboratory and SAGE in the Baksan laboratory. The first GALLEX results, in 1992, (and later SAGE) confirmed the solar neutrino problem, with a deficit smaller than for the chlorine experiment.

The figure summarizes the experimental situation in 1998. The two experiments observe about 60% of the predictions of the solar models. The rate is measured  in SNU’s (Solar Neutrino Unit) [one SNU corresponds to 10−36 capture per target atom per second].


Neutrino oscillation seen by SuperK in 1998


First result: First observation of neutrino oscillation from atmospheric neutrinos in the SuperKamiokande experiment.

The first observation of oscillation of atmospheric neutrinos was made by the SuperKamiokande experiment in 1998 [Fuk98a,Kaj98]. The figure represents the angular distribution of νe events (left column) and νμ events (right column). Upper (lower) figures are for low (high) energy events. The deficit, compared to predictions, of  νμ events coming from the antipodes (cos(θ)<0) is the signature that they have been transformed into another flavor during their path.

Mettre à gauche une figure de 1998 avant celle de 2004

In 2004, using only the high distance/energy (L/E) resolution event, SuperKamiokande showed that the measured νμ survival probability has a dip corresponding to the first minimum of the theoretical survival probability near L/E=(500km/GeV).  This was the first evidence that the neutrino survival probability obeys the sinusoidal function predicted by neutrino oscillations.See bottom figure [Ash04].






SNO and other solar neutrino results


First result: SNO solves the solar neutrino problem

Mettre d’abord la première figure de SNO en 2001 (figure 3 du papier Ahm01).

Using heavy water (D2O) as a target to measure solar neutrinos, the SNO experiment was able to measure all the neutrino flavours (νe,νμ,ντ). This gave the first indication of a non electron flavor component in the solar neutrino flux and enabled the first determination of the total flux of 8B neutrinos generated by the Sun [Ahm01]. The figure shows the flux of (νμ+ντ) 8B solar neutrinos versus the pure νe flux measured by SNO via the pure charged current reaction (CC). For the elastic reaction, the results of SNO and SuperKamiokande are combined; the diagonal band shows the total flux (νe+νμ+ντ) experimental and theoretical; the intercept of the diagonal band with the vertical νe flux gives the νμ+ντ flux.

This result was completed in 2002 by a direct measurement of neutral-current interactions [Ahm02] (and later with more precise measurements)]. SNO made then an unambiguous detection of the flavor change of  neutrinos emitted in the core of the Sun.

The lower figure summarizes in 2018 the ratios of measurements to solar model calculations for SNO and all other solar neutrino experiments(Homestake, GALLEX, SAGE, SuperKamiokande). The SNO NC (Neutral Current) measurement is close to “one” (all the neutrino flavors are detected). The values differ for the different experiments since they have different energy thresholds to detect solar neutrinos. It is clear from the figure that the neutrino flavor change is the favored solution to what is happening to neutrinos from the Sun.

Reference de la figure : proceedings de notre conférence.


Kamland first result in 2002


Summary: KamLAND observes neutrino oscillation
from nuclear reactors [Egu03]

KamLAND sees very well the oscillation of neutrinos from nuclear reactors. Data show the ratio of  the number of neutrinos observed to the number of neutrino expected if there were no neutrino oscillation. KamLAND was located at about 200 km of nuclear reactors and all the experiments before KamLAND were too close to the nuclear reactor (few km) to see the oscillation. The dashed curve shows the theoretical oscillation with the best fitting parameters for the KamLAND measurement’s point. The green area corresponds to the uncertainty on those parameters. This result reinforces the hypothesis of the so-called LMA solution of the solar neutrino problem.

Neutrino oscillation seen by KamLAND


First result: KamLAND sees full neutrino oscillation

Neutrino oscillation seen by KamLAND. The “Survival Probability” is computed from the number of electron anti-neutrinos produced by the nuclear reactor and detected by KamLAND. It depends on the ratio between the distance  KamLAND-nuclear reactor and the energy of the neutrinos. The measurement points shows clearly the oscillation phenomena and its dependence on L/E.

Regrouper les deux KamLAND en un seul avec les deux figures.

DayaBay, RENO and DOuble Chooz results


First result: Evidence for neutrino oscillation in reactor experiments.

From 2004, several neutrino detectors were built close to nuclear power plants to search for the third neutrino mixing angle θ13.

The figure summarizes the first results of the Double Chooz, Daya Bay and RENO experiments. For each  experiment, the data of the upper plot are the number of neutrinos detected as a function of their energy, while the lower plots show the ratio between the measurements and the theoretical expectation in the case of no neutrino oscillation (Double Chooz) or the ratio between the number of neutrinos detected in the far and near detectors (Daya Bay, RENO), the near detector being the reference where no neutrino oscillation has yet occured.

At the same time, the T2K experiment also found evidence for a positive θ13 angle from νe appearance in a νμ beam [Abe11a].

Planck CMB measurement


First result: The cosmological Planck experiment observes 3 neutrino families

The Planck experiment  provided a very good estimate of the number of neutrino families from the study of the Cosmic Microwave Background (CMB). The Planck satellite has measured the temperature of the CMB in all the directions of the Universe and looked at the temperature fluctuations for various angular scales (the l parameter on the x axis of the figure on the left). The first peak around l=100 corresponds to large fluctuations linked to baryogenesis and is called the baryonic acoustic peak. The red curve is a fit to the data, of which one parameter is the number of neutrino families. The best fit gives 3 neutrino families with an uncertainty of about 0.2 [Ade13].


Bah76J.N. Bahcall and R. Davis Solar Neutrinos: A Scientific Puzzle Science 191 (1976) 264
Bio87R.M. Bionta et al., IMB collaborationObservation of a neutrino burst in coincidence with supernova SN1987A in the Large Magellanic Cloud Phys. Rev. Lett. 58 (1987) 1494
Cha14J. Chadwick Intensitatsverteilung im magnetischen spektrum der beta-strahlen von radium B+CVerhandlungen der deutschen Physikalischen Gesellschaft 16 (1914) 383
Cle98B.T. Cleveland et al. Measurement of the solar electron neutrino flux with the Homestake chlorine detectorAstrophysical Journal 496 (1998) 505
Cow56C.L. Cowan, F. Reines, F.B. Harrison, H.W. Cruse and A.D. McGuire Detection of the free neutrino: a confirmationScience 124 (1956) 103, July 20, 1956
Dan62G. Danby, J.M. Gaillard, K. Goulianos, L.M. Lederman, N. Mistry, M. Schwartz and J. SteinbergerObservation of high energy neutrino reactions and the existence of two kinds of neutrinos Phys. Rev. Lett. 9 (1962) 36
Dav68R. Davis, D.S. Harmer, K.C. Hoffman Search for neutrinos from the Sun Phys. Rev. Lett. 20 (1968) 1205
Ell27C.D. Ellis and W.A. Wooster The Average Energy of Disintegration of Radium E Proc. Roy. Soc. A 117 (1927) 109
Gol58M. Goldhaber, L. Grodzins, A. Sunyar Helicity of neutrinos Phys. Rev. 109 (1958) 1015
Has73aF.J. Hasert et al. Search for elastic muon-neutrino electron scattering Phys. Lett. B46 (1973) 121 – Received Jul. 2, 1973
Has73bF.J. Hasert et al. Observation of neutrino-like interactions without muon or electron in the Gargamelle neutrino experiment Phys. Lett. B46 (1973) 138 – Received July 23, 1973
Hir87K.S. Hirata et al., Kamiokande collaboration Observation of a neutrino burst from the supernova SN1987A Phys. Rev. Lett. 58 (1987) 1490
Los97Los AlamosCelebrating the neutrinoLos Alamos Science 25
Pon59bB. Pontecorvo Electron and muon neutrinos Soviet Physics JETP 10 (1960) 1236 ; J. Exp. Theoret. Phys. 37 (1959) 1751
Rei56Frederick Reines and Clyde Cowan jr.The neutrinoNature 178 (1956) 446
Sch60M. Schwartz Feasibility of using high energy neutrinos to study the weak interactionsPhys. Rev. Lett. 4 (1960) 306


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