Solar neutrino

[citation needed] Neutrinos are elementary particles with extremely small rest mass and a neutral electric charge.

The timeline of solar neutrinos and their discovery dates back to the 1960s, beginning with the two astrophysicists John N. Bahcall and Raymond Davis Jr.

Davis developed the idea of taking hundreds of thousands of liters of perchloroethylene, a chemical compound made up of carbon and chlorine, and searching for neutrinos using a chlorine-argon detector.

[1] By conducting the experiment deep underground, Bahcall and Davis were able to avoid cosmic ray interactions which could affect the process and results.

[2] The entire experiment lasted several years as it was able to detect only a few chlorine to argon conversions each day, and the first results were not yielded by the team until 1968.

[2] At the time, it was unknown if there was an error with the experiment or with the calculations, or if Bahcall and Davis did not account for all variables, but this discrepancy gave birth to what became known as the solar neutrino problem.

[3] Davis even repeated his experiment changing the sensitivity and other factors to make sure nothing was overlooked, but he found nothing and the results still showed "missing" neutrinos.

The goal of the Borexino experiment is measuring low energy, typically below 1 MeV, solar neutrinos in real-time.

[9] The detector is a complex structure consisting of photomultipliers, electrons, and calibration systems making it equipped to take proper measurements of the low energy solar neutrinos.

The excited beryllium-8 nucleus then splits into two helium-4 nuclei:[12] The highest flux of solar neutrinos come directly from the proton–proton interaction, and have a low energy, up to 400 keV.

The detectors that use gallium are most sensitive to the solar neutrinos produced by the proton–proton chain reaction process, however they were not able to observe this contribution separately.

In 2012 the same collaboration reported detecting low-energy neutrinos for the proton–electron–proton (pep reaction) that produces 1 in 400 deuterium nuclei in the Sun.

[17][18] The detector contained 100 metric tons of liquid and saw on average 3 events each day (due to 11C production) from this relatively uncommon thermonuclear reaction.

In 2014, Borexino reported a successful direct detection of neutrinos from the pp-reaction at a rate of 144±33/day, consistent with the predicted rate of 131±2/day that was expected based on the standard solar model prediction that the pp-reaction generates 99% of the Sun's luminosity and their analysis of the detector's efficiency.

[citation needed] Frederick Reines, from the University of California at Irvine, and Clyde Cowan were the first astrophysicists to detect neutrinos in 1956.

Pontecorvo, known as the first astrophysicist to suggest the idea neutrinos have some mass and can oscillate, never received a Nobel Prize for his contributions due to his passing in 1993.[speculation?]

[23] McDonald, along with Japanese physicist Kajita Takaaki both received a Nobel Prize for their work discovering the oscillation of neutrinos in 2015.

This research, published in 2017, aimed to solve the solar neutrino and antineutrino flux for extremely low energies (keV range).

Diagram showing the Sun's components. The core is where nuclear fusion takes place, creating solar neutrinos.
Diagram of the Homestake experiment set-up
Borexino detector exterior
Solar neutrinos ( proton–proton chain ) in the standard solar model
Solar Neutrino Generation
The greatest number of solar neutrinos are direct products of the proton–proton reaction (tall, dark blue curve on the left). They have a low energy – only reaching up to 400 keV. There are several other significant production mechanisms, with energies up to 18 MeV. [ 13 ]
Theoretical curves of survival probability of solar neutrinos that arrive on day (orange, continuous) or on night (purple, dashed), as a function of the energy of the neutrinos. Also shown the four values of the energy of the neutrinos at which measurements have been performed, corresponding to four different branches of the proton–proton chain.
Raymond Davis Jr receives the Medal of Science from President George W. Bush .