The neutrino experiment, also called the Cowan and Reines neutrino experiment, was performed by Clyde L. Cowan and Frederick Reines in 1956. This experiment confirmed the presence of the neutrino—a very small and neutrally charged subatomic particle. Clyde Lorrain Cowan Jr (1919–1974) was a captain in the United States Army Air Force. ... Frederick Reines Frederick Reines (March 16, 1918 - August 26, 1998) was an American physicist. ... 1956 was a leap year starting on Sunday of the Gregorian calendar. ... The neutrino is an elementary particle. ... Charge is a word with many different meanings. ... A subatomic particle is a particle smaller than an atom: it may be elementary or composite. ...

History

In the 1930s, through the study of beta decay, it was apparent that a third particle, one of nearly no mass and with neutral charge existed and was not observed. In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... Charge is a word with many different meanings. ...

This was due to a continuous spread of kinetic energy and momentum values for electrons emitted in beta decay. The only way this was possible was if there was a particle of neutral charge and almost no mass (or possibly no mass) produced in the decay. Kinetic energy (also called vis viva, or living force) is energy possessed by a body by virtue of its motion. ... In physics, momentum is a physical quantity related to the velocity and mass of an object. ... Properties The electron is a subatomic particle. ... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... Charge is a word with many different meanings. ...

Potential for experiment

In beta decay the predicted particle, the electron antineutrino () - should interact with a proton to produce a neutron and positron - the antimatter counterpart of the electron. In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... The neutrino is an elementary particle. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle of the electron. ... Antimatter is matter that is composed of the antiparticles of those that constitute normal matter. ... Properties The electron is a subatomic particle. ...

The positron quickly finds an electron, and they annihilate each other - a process known as annihilation. The two resulting gamma rays (γ) are easily detectable. The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle of the electron. ... Properties The electron is a subatomic particle. ... Annihilation occurs when a particle collides with an antiparticle. ... This article is about electromagnetic radiation. ...

The setup

In this experiment, they used a nuclear reactor as they were expected to produce neutrino fluxes on the order of 10¹² to 10¹³ neutrinos per second per cm², far higher than any attainable flux from other radioactive sources. Nuclear power station at Leibstadt, Switzerland. ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ...

The neutrinos would then interact (as shown above) with protons in a tank of water, creating neutrons and positrons. Each positron would create a pair of gamma rays when it annihilated with an electron. For alternative meanings see proton (disambiguation). ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle of the electron. ... This article is about electromagnetic radiation. ... Properties The electron is a subatomic particle. ...

The gamma rays were detected by placing a scintillator material in a tank of water. The scintillator material gives off flashes of light in response to the gamma rays and the light flashes are detected by photomultiplier tubes. A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ...

However, this experiment wasn't conclusive enough, so they came up with a second layer of certainty.

They would detect the neutrons by placing cadmium chloride into the tank. Cadmium is a highly effective neutron absorber (and so finds use in nuclear control rods) and gives off a gamma ray when it absorbes a neutron. Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... Cadmium chloride is a white crystalline compound of cadmium and chlorine, with the formula CdCl2. ... General Name, Symbol, Number cadmium, Cd, 48 Chemical series transition metals Group, Period, Block 12, 5, d Appearance silvery gray metallic Atomic mass 112. ... A control rod is a rod made of a chemical element capable of absorbing many neutrons without decaying themselves. ...

The arrangement was such that the gamma ray from the cadmium would be detected 5 microseconds after the gamma ray from the positron, if it were truly produced by a neutrino. General Name, Symbol, Number cadmium, Cd, 48 Chemical series transition metals Group, Period, Block 12, 5, d Appearance silvery gray metallic Atomic mass 112. ... A microsecond is an SI unit of time equal to one millionth (10-6) of a second. ...

The results

They performed the experiment preliminarily at Hanford, but later moved the experiment to the Savannah River Plant near Augusta, Georgia where they had better shielding against cosmic rays. This shielded location was 11 m from the reactor and 12 m underground. Hanford is the name of some places in the United States of America: Hanford, California Hanford, Iowa Hanford, Maine Hanford, New Jersey Hanford, Ohio Hanford, Washington This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... The Savannah River is a major river in the southeastern United States, forming most of the border between the states of South Carolina and Georgia. ... The seal of the City of Augusta Augusta is a city located in the state of Georgia. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ...

They used two tanks with a total of about 200 liters of water with about 40 kg of dissolved CdCl₂. The water tanks were sandwiched between three scintillator layers which contained 110 five-inch (127 mm) photomultiplier tubes. A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ...

After months of data collection, they had accumulated data on about three neutrinos per hour in their detector. To be absolutely sure that they were seeing neutrino events from the detection scheme described above, they shut down the reactor to show that there was a difference in the number of detected events. The neutrino is an elementary particle. ... The neutrino is an elementary particle. ...

They had predicted a cross-section for the reaction to be about 6×10⁻⁴⁴ cm² and their measured cross-section was 6.3 ×10⁻⁴⁴ cm². Their results were published in 1956. 1956 was a leap year starting on Sunday of the Gregorian calendar. ...

Frederick Reines was honored with the Nobel Prize in 1995 for his work on neutrino physics. Frederick Reines Frederick Reines (March 16, 1918 - August 26, 1998) was an American physicist. ... Sir Edward Appletons medal Photographs of Nobel Prize Medals. ... 1995 was a common year starting on Sunday of the Gregorian calendar. ... The neutrino is an elementary particle. ... The willingness to question previously held truths and search for new answers resulted in a period of major scientific advancements, now known as the Scientific Revolution. ...

Further reading

• Cowan and Reines Neutrino Experiment
• Decay of the Neutron
• Beta Decay
• Electron Neutrinos and Antineutrinos
• Subatomic Particles