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Muon 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
Second
Lepton
weak, gravity
νμ
Muon antineutrino ( νμ )
Small but non-zero
0 e
none
¹/₂
¹/₂
-1
left-handed
MUON NEUTRINO
General
The muon neutrino, denoted by the symbol νμ and possessing zero electric charge, is an elementary particle. It constitutes the second generation of leptons along with the muon, giving rise to its name. Leon Lederman, Melvin Schwartz, and Jack Steinberger discovered the muon neutrino in 1962, earning them the Nobel Prize in Physics in 1988.
The existence of the muon neutrino was proposed by physicists in the 1940s, with the first paper on the subject being Shoichi Sakata and Takesi Inoue's two-meson theory in 1942. Lederman, Schwartz, and Steinberger experimentally confirmed the muon neutrino at the Brookhaven National Laboratory.
An intriguing episode in the muon neutrino's history involved reports in 2011 suggesting that they were traveling faster than light. However, subsequent investigations, including experiments by the ICARUS team, revealed faulty elements in the fiber optic timing system at Gran Sasso. After correction, the neutrinos' apparent super-luminous propagation was debunked, and their speed was found to be consistent with the speed of light within experimental errors.
Symbol and Charge:
The muon neutrino is represented by the symbol νμ.
It is electrically neutral, carrying zero electric charge.
Generation and Lepton Family:
Muon neutrinos belong to the second generation of leptons.
Leptons are a family of elementary particles that includes electrons, muons, and taus, each associated with their corresponding neutrinos.
Discovery:
The muon neutrino was first hypothesized to exist in the 1940s, and its theoretical groundwork was laid by physicists such as Shoichi Sakata and Takesi Inoue in 1942.
Experimental confirmation came in 1962 when Leon Lederman, Melvin Schwartz, and Jack Steinberger conducted an experiment at the Brookhaven National Laboratory, earning them the Nobel Prize in Physics in 1988.
Mass:
Neutrinos were long believed to be massless according to the Standard Model, but experiments have since established that neutrinos, including muon neutrinos, do have small but non-zero masses.
Spin :
Neutrinos, including muon neutrinos, are fermions, which means they have intrinsic angular momentum or spin. The spin of a particle is a fundamental property that characterizes its quantum behavior.
Muon neutrinos, like all neutrinos, are classified as spin-1/2 particles. This designation means they possess half-integer spin. Specifically, the spin of muon neutrinos is 1/2 ħ, where ħ is the reduced Planck constant. This intrinsic angular momentum is a quantum property that influences the particle's interactions and behavior.
The spin of neutrinos is crucial in the context of weak interactions, as neutrinos predominantly participate in weak force processes. Understanding the spin properties of neutrinos is essential for describing their interactions with other particles and for developing a comprehensive understanding of the fundamental forces and particles in the universe.
It's worth noting that the spin of neutrinos does not refer to an actual rotation in the classical sense but is a quantum mechanical property that governs the behavior of these subatomic particles.
Flavor Oscillation:
Neutrinos are known to undergo flavor oscillations, where they change from one flavor (e.g., muon neutrino) to another (e.g., electron or tau neutrino) as they travel through space. This phenomenon is a clear indication that neutrinos have mass.
Interaction with matter:
Muon neutrinos, like all neutrinos, interact very weakly with matter. The primary mode of interaction for neutrinos, including muon neutrinos, is through the weak force, one of the fundamental forces in the Standard Model of particle physics. The weak force is responsible for processes such as beta decay and interactions involving neutrinos.
Muon neutrinos specifically are associated with the creation and decay of muons. Here are some of the processes where muon neutrinos are created:
Muon Decay:
Muon neutrinos are primarily produced in the decay of muons. When a muon (a heavier cousin of the electron) undergoes weak decay, it transforms into a muon neutrino, a muon neutrino antiparticle, and an electron (or positron) along with associated neutrinos.
Pion Decay:
Muon neutrinos can be produced in the decay of charged pions (π+ and π-) that are created in high-energy processes, such as in particle accelerators or cosmic ray interactions with the Earth's atmosphere. The decay chain involves the production of muon neutrinos, muons, and electron neutrinos.
Kaon Decay:
Similar to pions, muon neutrinos are produced in the decay of charged kaons (K+ and K-) in processes involving high-energy particle interactions. The decay of kaons leads to the production of muon neutrinos, muons, and electron neutrinos.
Muon Capture (OMC) :
Muon capture is the capture of a negative muon by a proton, usually resulting in production of a neutron and a neutrino, and sometimes a gamma photon. Muon capture by heavy nuclei often leads to emission of particles; most often neutrons, but charged particles can be emitted as well.
Ordinary muon capture (OMC) involves capture of a negative muon from the atomic orbital without emission of a gamma photon:
Radiative muon capture (RMC) is a radiative version of OMC, where a gamma photon is emitted:
Nuclear Reactions:
In certain nuclear reactions, especially those involving weak interactions, muon neutrinos can be produced. These reactions may occur in astrophysical environments, such as the core of a supernova, where high-energy processes lead to the creation of muons and their subsequent decay into muon neutrinos.
High-Energy Cosmic Rays:
Muon neutrinos can be generated in the interactions of high-energy cosmic rays with matter in the universe. These cosmic rays can produce a variety of particles, including muons, which then decay to produce muon neutrinos.
Colliders and Particle Accelerators:
In experimental settings like particle colliders and accelerators, high-energy collisions between particles can generate various particles, including muons and their associated neutrinos.
Figure 276 - Muon decay into a Muon Neutrino
Figure 277 - Pion ( decay into Muon Neutrino
Figure 278 – Kaon (K+) decay into Muon Neutrino
Figure 279 - Ordinary muon capture creating Muon Neutrino
Figure 280 - Radiative muon capture (RMC)
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