Historical plots

1914

First result: Continuous beta spectrum measurement
[Cha14]

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

1927

First result: Continuous beta spectrum measurement
[Ell27]

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.

The continuous shape of the spectrum, unexpected for a two-body decay, triggered Wolfgang Pauli to “invent” the neutrino in his letter of December 1930.

1951

Scheme of the first neutrino project of F. Reines and C. Cowan
[Los97]

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.

1956

First result: Evidence for the neutrino by F. Reines and C. Cowan
[Rei53,Cow56,Rei56]

Fred Reines and Clyde Cowan performed a first experiment in 1953, close to the Hanford nuclear power plant [Rei53]. This was the Poltergeist project, whose detector is shown by the photograph. 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 their detector [Cow56,Rei56].

[The generic term “neutrino” is used, but, to be exact, nuclear reactors emit anti-electron-neutrinos νe].

1958

First result: The Goldhaber experiment shows that neutrinos are left-handed
[Gol58]

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]]

1962

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 Bruno Pontecorvo [Pon59b] and Melvin Schwartz [Sch60]. To observe this new family, Schwartz proposed the scheme shown in the upper figure. Difficult to imagine a more simple scheme 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 (see the photograph). Neutrinos come from the decay of pions produced in the proton interactions. About 100 muon-neutrino νμ interactions were observed [Dan62].

1965-1970

First neutrino interactions in bubble chambers [Pat65,Arg70]

The first neutrino interactions in (heavy liquid) bubble chambers were observed at CERN in 1964-1965 [Pat65] (no picture presently available).

The photograph shows the first neutrino-proton interaction observed on November 13th 1970 in the 12-ft hydrogen bubble chamber of the Argonne National Laboratory [Arg70].

1972

First result: Measurement of neutrino-nucleon cross-section
[Per72]

Experimental measurements of the cross section (probability of interaction) of νμ on neutrons within nucleus of deuterium atoms. First figure shows that there is no significant increase of the cross-section with energy and confirms the very low value predicted by theory [reference still to be found].

The paper [Per72] gives also several cross sections of neutrino νμ and antineutrino νμ interactions. Second figures shows the elastic neutrino crosssections for various A mass hypothesis. Last figure displays the neutrino cross section on nucleon, showing the expected linear rising as a function of energy.

1973

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

This 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 (NC) interaction.

The discovery of the hadronic neutral current is shown on the lower figure [Has73b], where can be seen the number of NC (neutral current) and CC (charged current) events detected and their ratio with respect to their position in the bubble chamber, for neutrinos and anti-neutrinos.

In addition to the neutral current discovery, later measurements by Gargamelle and next experiments confirmed with great precision that NC/CC for neutrinos is xxx while NC/CC for anti-neutrinos is yyy

1968-1976

First result: Homestake solar neutrino experiment and the solar neutrino problem.
[Dav68,Bah76]

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.

1987

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.

1989

First result : LEP finds 3 neutrino families
[Aar89,Ade90,Akr89,Dec89]

In a seminar at CERN on 13 october 1989, the four LEP experiments (ALEPH, DELPHI, L3 and OPAL) presented the first results on the Z line shapes. This measurement of the Z width provides information about the number of neutrino families. The data points shown here are the average hadronic cross-sections. The different curves on Alpeh and L3 plots correspond to the prediction for 2, 3 or 4 light neutrino species (the cross section decreases when the number of neutrino species increases). Three neutrino species is strongly favoured.

to be added: Figure 2004 from Ash04

1998

First result: First observation of neutrino oscillation from atmospheric neutrinos in the SuperKamiokande experiment.
[Fuk98b,Kaj98,Ash04]

The first observation of oscillation of atmospheric neutrinos was made by the SuperKamiokande experiment in 1998 [Fuk98a,Kaj98]. The upper 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.

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=(500 km/GeV).  This was the first evidence that the neutrino survival probability obeys the sinusoidal function predicted by neutrino oscillations.The lower figure [Ash04].shows this survival probability as a function of L/E.

2001

First result: SNO solves the solar neutrino problem
[Ahm01,Ahm02]

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 upper 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 but the values show clearly that the neutrino flavor change is the favored solution to what is happening to the solar neutrinos.
Figure ref : proceedings of the Neutrino History Conference, 5-7 sept. 2018.

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.

2004

First result: KamLAND sees full neutrino oscillation
[Ara05b]

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.

2011

First result: Evidence for neutrino oscillation in reactor experiments.
[Abe11b,An12,Ahn12]

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].

2013

First result: The cosmological Planck experiment strongly favours 3 neutrino families
[Ade13]

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].

1998

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).

1992-1998

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].

2000

Summary: LEP finds 3 families of light neutrinos
[Blo18]

In 1989, the first LEP measurements of the Z width provided information about the number of families of light neutrinos. The result has been improved in the following years and is shown in the left figure. The data points show theaverage hadronic cross-sections. 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. As mentioned on the plot, the errors bars have been increased by factor 10 to make them visible.

The figure corresponds to the data in 2000. The history is summarized in [Blo18].

2013

Summary: neutrino-nucleon total cross-section measurements
[Scu13]

The Ph.D. thesis by Scully in 2013 [Scu13] gives a brief review of the present knowledge of the neutrino and antineutrino cross sections. The figure on the left shows the total νμ CC (full line) and NC (dotted line) cross sections on deuterium as a function of the neutrino energy, compared with data on νμ CC from a variety of targets. The plot shows the linear increase of the cross-section with energy.

More information on neutrino cross-sections are found in [Scu13].