Electron neutrino
Composition :
Statistics :
Generation :
Family :
Interaction forces :
Symbol :
Antiparticle :
Mass :
Decays into :
Electric charge :
Color charge
Spin :
Weak isospin :
Weak hypercharge :
Chirality :
Elementary particle
Fermionic
First
Lepton
weak,
gravity
νₑ
Electron antineutrino ( νₑ )
Small but non-zero
0 e
none
¹/₂
¹/₂
-1
left-handed
_
ELECTRON NEUTRINO
General
The electron neutrino, a key participant in the Standard Model of particle physics, represents one of the three neutrino flavors alongside the muon and tau neutrinos. This electrically neutral particle, nearly massless and interacting solely through the weak force, exhibits intriguing properties. Neutrino flavor oscillations, a phenomenon observed in neutrinos, highlight the electron neutrino's ability to transform into muon or tau neutrinos during propagation, challenging traditional views of particle identities. Solar neutrino studies, particularly focused on electron neutrinos, provide insights into solar processes.
Originally assumed massless in the Standard Model, electron neutrinos were later confirmed to possess small, elusive masses, prompting ongoing research into the precise mass hierarchy. The electron neutrino's role extends beyond theoretical frameworks, impacting astrophysics and particle physics alike. As investigations into the neutrino family continue, the electron neutrino remains a focal point for understanding fundamental aspects of the cosmos and exploring potential extensions to the Standard Model. This pursuit unlocks doors to new physics, pushing the boundaries of scientific knowledge.
Electron Neutrino Properties
Mass: Neutrinos are extremely difficult to detect, and their precise masses are still not precisely known. However, experiments have established that neutrinos have masses, although they are very small. The masses of neutrinos are at least six orders of magnitude smaller than the masses of the other known elementary particles. The absolute values of the neutrino masses are currently the subject of ongoing research.
Electric Charge Neutrality: Neutrinos are electrically neutral particles, which means they do not carry an electric charge. The electron neutrino, specifically, has zero electric charge. This neutrality is one of the reasons neutrinos interact so weakly with matter, making them challenging to detect.
Spin: The electron neutrino is a fermion and, like all fermions, has half-integer spin. It has a spin of 1/2. Spin is a fundamental property of particles and is related to their intrinsic angular momentum. Neutrinos, being fermions, obey the Pauli exclusion principle, which means no two identical neutrinos can occupy the same quantum state simultaneously.
Flavor: Neutrinos come in three flavors: electron neutrino (νe), muon neutrino (νμ), and tau neutrino (ντ). Each flavor is associated with a corresponding charged lepton: electron, muon, and tau, respectively. The flavors can oscillate, meaning a neutrino produced as one flavor can change into another flavor as it travels through space.
Interaction with Matter: Electron neutrinos interact with matter primarily through the weak nuclear force, one of the fundamental forces in the Standard Model of particle physics. Neutrinos interact so weakly with matter that they can pass through large volumes of it without being significantly affected. Here are some key aspects of the interaction of electron neutrinos with matter:
Weak Interaction: The primary mode of interaction for neutrinos is the weak force, which is responsible for processes such as beta decay. In the context of beta decay, a neutron can transform into a proton by emitting a W- boson, which then decays into an electron and an electron antineutrino (for beta-minus decay) or a neutrino (for beta-plus decay). Neutrinos themselves are produced in such processes, and their detection often involves the inverse process.
Low Cross Section: Neutrinos have an extremely low interaction cross section, meaning they are much less likely to interact with other particles than, for example, charged particles like electrons or protons. This property makes neutrinos challenging to detect and is one reason why they can pass through large amounts of matter without being significantly affected.
Flavor Change (Oscillation): Neutrinos can change flavor as they travel through space, a phenomenon known as neutrino oscillation. This implies that an electron neutrino produced in a certain process may be detected later as a different flavor neutrino (muon or tau neutrino). This behavior is a consequence of neutrinos having non-zero masses and is a unique feature of neutrino interactions.
Solar Neutrinos: Electron neutrinos are produced in significant quantities in nuclear reactions in the Sun. The study of solar neutrinos has provided important information about neutrino properties and helped confirm the phenomenon of neutrino oscillation.
Detection Challenges: Detecting electron neutrinos is challenging due to their weak interaction with matter. Neutrino detectors are often designed to be very large to increase the chances of an interaction occurring. Technologies such as liquid scintillators, water Cherenkov detectors, and other innovative approaches are employed in experiments to detect the rare interactions of neutrinos with matter.
Creation and Detection
Beta Decay:
One of the primary processes through which electron neutrinos are generated is beta decay. In beta-minus decay, a neutron transforms into a proton by emitting a W- boson, which then decays into an electron and an electron antineutrino.
In beta-plus decay, a proton transforms into a neutron, emitting a W+ boson, which decays into a positron and an electron neutrino
These processes occur in various nuclear reactions, such as those in the Sun or in particle accelerators.
Related Papers : See β-decay in chapter about up quark and down quark.
Nuclear Reactions in the Sun
In the Sun, electron neutrinos are produced in nuclear reactions, particularly through the proton-proton chain and the carbon-nitrogen-oxygen (CNO) cycle. In these reactions, hydrogen nuclei (protons) are fused into helium, releasing energy in the form of photons and producing electron neutrinos.
Supernovae
During a supernova explosion, a massive star undergoes a collapse and then rebounds, ejecting layers of its outer material into space. Neutrinos, including electron neutrinos, are produced abundantly in the intense environment of a supernova, and their detection can provide crucial information about the processes occurring during such astronomical events.
Near the end of life, a massive star is made up of onion-layered shells of elements with an iron core. During the early stage of the collapse, electron neutrinos are created through electron-capture on protons bound inside iron-nuclei. [3]
Experimental Methods and Detectors for Electron Neutrinos:
Cherenkov Detectors: Cherenkov detectors exploit the Cherenkov radiation produced when charged particles, such as electrons generated by neutrino interactions, travel through a medium at a speed greater than the phase velocity of light in that medium. Water Cherenkov detectors, like the Super-Kamiokande experiment, use large volumes of water as a target. The emitted Cherenkov light is then detected by photomultiplier tubes, allowing researchers to identify the presence of neutrinos.
Scintillation Detectors: Scintillation detectors use materials that emit flashes of light (scintillations) when charged particles pass through them. Liquid scintillator detectors, such as the KamLAND experiment, use organic liquids that emit light when interacting with neutrinos. By detecting the scintillation light, researchers can identify neutrino interactions.
Neutrino Telescopes: Neutrino telescopes are large detectors positioned deep underwater or underground to reduce interference from cosmic rays. IceCube, for example, is a neutrino observatory located at the South Pole, consisting of a cubic kilometer of ice instrumented with optical sensors. These detectors can capture the Cherenkov radiation produced by neutrino interactions.
Radiochemical Detectors: Some experiments use radiochemical methods to detect neutrinos indirectly. For instance, the Homestake experiment used a large tank of cleaning fluid (perchloroethylene) to detect electron neutrinos from the Sun. Neutrino interactions produced radioactive isotopes that could be chemically separated and counted.
Particle accelerators, such as those used in neutrino factories, can produce high-intensity neutrino beams. Detectors situated at a distance from the source can then measure the neutrino interactions. The MINOS and T2K experiments, for example, study neutrino oscillations using beams generated at accelerators.
Figure 271 - Feynman diagram of β⁻- decay creating ₑ
Figure 272 - Feynman diagram of β+- decay creating νe
Figure 273 - Solar neutrinos (proton–proton chain) in the standard solar model
(a) Neutronization phase (b) In-fall of material and neutrino trapping (c) Generation of shock wave and neutrinos burst (d) Stalling of shock wave (e) Neutrino heating (f) Explosion
Figure 274 - Evolutionary stages of the core-collapse supernova
Neutrino Oscillations
See also “Neutrino Oscillations” in "Leptons"
Figure 275 - Neutrino Oscillations
References
[1] Pagliaroli, Giulia; Vissani, Francesco; Costantini, Maria Laura; Ianni, Aldo (2009). "Improved analysis of SN1987A antineutrino events". Astroparticle Physics. 31 (3): 163–176. arXiv:0810.0466. Bibcode:2009APh....31..163P. doi:10.1016/j.astropartphys.2008.12.010. S2CID 119089069
[2] Source : Fermilab. LBNF/DUNE gears up for next stage of construction in South Dakota. Diana Kwon. July 2023
[3] Spurio, Maurizio (2018). Probes of Multimessenger Astrophysics. Astronomy and Astrophysics Library. Bibcode:2018pma..book.....S. doi:10.1007/978-3-319-96854-4. ISBN 978-3-319-96853-7. ISSN 0941-7834
[4] Solar Neutrino - Wikipedia