Tau 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
Third
Lepton
weak,
gravity
ντ
Muon antineutrino ( ντ )
Very small but non-zero
0 e
none
¹/₂
¹/₂
-1
left-handed
_
TAU NEUTRINO
General characteristics
The tau neutrino is one of the three types of neutrinos, which are elementary particles that belong to the lepton family. Neutrinos are extremely elusive and interact very weakly with matter, making them challenging to detect. The three types of neutrinos are associated with the three charged leptons: the electron neutrino (νe), the muon neutrino (νμ), and the tau neutrino (ντ). Each type of neutrino is associated with a corresponding charged lepton: the electron, muon, and tau, respectively.
Fundamental Properties:
Mass: Neutrinos were long believed to be massless, but experiments have now shown that they have tiny, non-zero masses. The exact masses of neutrinos are not precisely known, but they are much smaller than those of other elementary particles.
Charge: Neutrinos are neutral particles, meaning they carry no electric charge.
Generation and Interactions:
Tau neutrinos are produced in various astrophysical processes, such as nuclear reactions in the Sun, supernovae explosions, and cosmic ray interactions in the Earth's atmosphere.
Neutrinos interact very weakly with matter, primarily via the weak force. This weak interaction makes them challenging to detect, and they can pass through vast amounts of matter without being significantly affected.
Flavor Oscillations:
Neutrinos are known to undergo flavor oscillations as they travel through space. This phenomenon implies that a neutrino of one flavor (e.g., ντ) can change into another flavor (e.g., νe) as it propagates. This discovery has important implications for our understanding of neutrino properties and the Standard Model of particle physics.
Detection:
Detecting tau neutrinos is a complex task due to their weak interactions. Experiments often involve large detectors and the observation of secondary particles produced in neutrino interactions.
Fermilab has his DONUT detector. The 50-foot-long DONUT detector recorded six million potential interactions. The crucial component is the three-foot-long target station, which contains emulsion to record particle tracks, in particular the tracks of tau leptons. To reduce the data to about 1000 candidate neutrino events, other parts of the detector provided important information. They allowed scientists to locate promising tracks in the emulsion to within a few millimeters. These small emulsion areas then underwent careful analysis, eventually leading to the identification of five tau neutrino events.
Role in Particle Physics:
Neutrinos play a crucial role in particle physics, providing insights into the weak force and the structure of matter at the subatomic level. The study of neutrinos is essential for understanding the properties of the universe, including its composition and evolution.
Figure 284 - DONUT detector for direct observation of Tau Neutrinos [3]
Creation of Tau Neutrinos
Nuclear Reactions in the Sun
In the core of the Sun, where temperatures and pressures are extremely high, nuclear fusion reactions take place. The primary fusion process involves the conversion of hydrogen nuclei (protons) into helium nuclei. During these reactions, several intermediate particles are produced, including positrons and electron neutrinos (νe).
The main reaction is the proton-proton (p-p) chain, where four protons eventually produce a helium-4 nucleus, releasing energy. Electron neutrinos are produced in these reactions. However, as neutrinos travel from the Sun's core to the surface, flavor oscillations can occur, leading to the creation of tau neutrinos and muon neutrinos.
Supernovae Explosions:
In the intense environment of a supernova explosion, neutrinos are produced through various processes. During the core collapse, as a massive star reaches the end of its life, electron neutrinos, muon neutrinos, and tau neutrinos are generated. These neutrinos carry away a significant fraction of the gravitational energy released during the supernova event.
Neutrinos play a crucial role in the supernova dynamics, helping to shock heat the outer layers of the star and driving the explosion.
Cosmic Ray Interactions:
Cosmic rays are high-energy particles that originate from sources beyond our solar system. When cosmic rays, mostly protons, collide with particles in the Earth's atmosphere, they produce a cascade of secondary particles, including tau leptons. These tau leptons can subsequently decay, generating tau neutrinos.
The process involves the interaction of cosmic ray protons with atmospheric nuclei, producing a variety of particles in a shower-like cascade.
Particle Colliders:
In high-energy particle colliders, such as the Large Hadron Collider (LHC), particles are accelerated to near the speed of light and collided. In these collisions, a variety of particles are produced, including tau leptons and their associated neutrinos.
The creation of tau neutrinos in collider experiments typically involves the decay of heavier particles into tau leptons, which subsequently decay into tau neutrinos and other particles.
Tau Decay
In some case taus are decaying producing a tau neutrino in one of the following ways
Decays of Heavy Mesons and Baryons:
Heavy mesons and baryons, which contain heavy quarks, can decay into lighter particles, including tau leptons and tau neutrinos. The specific decay processes depend on the type of meson or baryon involved.
For example, B mesons (containing a bottom quark) can decay into tau leptons and tau neutrinos, contributing to the production of tau neutrinos in certain experimental setups.
Figure 285 - Example of quasi-elastic scattering
Figure 287 - Tau decay producing an tau neutrino
Figure 286 - Ds to Tau topology [1]
Figure 288 - Schematic picture of the B0 → K∗0 [2]
Tau Neutrino Decay
Figure 289 - neutral current mediated tau neutrino splitting
Online Library
References
[1] DsTau Collaboration; Aoki, S.; Ariga, A.; Ariga, T.; Dmitrievsky, S.; Firu, E.; Forshaw, D.; Fukuda, T.; Gornushkin, Y.; Guler, A.M.; et al. DsTau: Study of tau neutrino production with 400 GeV protons from the CERN-SPS. J. High Energy Phys. 2020, 2020, 1–26. [Google Scholar]
[2] b → sτ +τ − Physics at Future Z Factories. Lingfeng Li,and Tao Liub. arXiv:2012.00665v1
[3] Source : Fermilab. https://www.fnal.gov/pub/inquiring//physics/neutrino/discovery/donut_detector.html