Antidown Quark
Composition :
Statistics : Generation :
Family :
Interaction forces :
Symbol :
Antiparticle :
Mass :
Decays into :
Electric charge :
Color charge
Spin :
Elementary antiparticle
Fermionic
First
Quark
strong, weak,
electromagnetic force
gravity
d
Down quark ( d )
2.2 MeV/c²
stable or
d + e⁺ + νₑ
⅓ e
Yes
¹/₂
+ 0,5
- 0,4
_
ANTIDOWN QUARK
General
The antidown quark, often denoted as "d̄" or "anti-d," is the antiparticle counterpart of the down quark. Antiparticles have opposite electric charges and other quantum numbers compared to their corresponding particles. Here's a detailed description of the antidown quark and its context in quantum physics and quantum field theory:
Quantum Numbers of the Antidown Quark:
The antidown quark carries a positive electric charge of +1/3e, which is the opposite of the down quark's charge.
Like other quarks, the antidown quark also possesses color charge. Quarks come in three "colors" (red, green, blue), while antiquarks come in anticolors (anticolor charges: antired, antigreen, antiblue).
Role in Particle Interactions :
Antiquarks, including the antidown quark, participate in strong force interactions just like their corresponding quarks. They can combine with quarks to form mesons, which are color-neutral bound states.
Quantum Field Theory (QFT) and Antiparticles:
In the framework of quantum field theory (QFT), quarks and antiquarks are described as excitations of their respective fields.
Quantum Chromodynamics (QCD) is the quantum field theory that governs the strong nuclear force and describes the interactions between quarks and gluons. Antiquarks interact with gluons in a manner consistent with the theory.
Experimental Observations:
Antiparticles, including antiquarks, have been observed in high-energy particle physics experiments. These experiments confirm the predictions of the Standard Model of particle physics, which includes quarks and antiquarks.
Combinations with antidown quarks
Mesons:
Pi Mesons (π): Antidown quarks can combine with up quarks (u) or antidown quarks to form neutral or charged pi mesons.
Pion-plus (π+) meson
Pion-neutral (π⁰) meson
Baryons
Xi Baryons (Ξ): Antidown quarks can combine with strange quarks and bottom quarks (b) to form xi baryons.
Lambda Baryon (Λ): Antidown quarks can combine with up quarks and strange quarks (s) to form lambda baryons.
Figure 77 – Pion-plus ( π+) meson
Figure 78 - Pion-neutral (π⁰) meson
Figure 79 - Ξ baryon
Figure 80 - Neutral Λ0 baryon
Creation of antidown quarks
Weak decays of particles can lead to the creation of anti-down quarks. For example, in the decay of a W boson, which is responsible for weak interactions, an up quark can transform into an anti-down quark through the exchange of a W boson. Some examples :
K+ decay (see figure 33)
K0 decay (see figure 34)
η decay (see figure 36)
D-meson decay (see figure 37)
Ψ decay (see figure 42)
gluon-gluon fusion (see figure 43)
Also the decay of a strange quark can lead to the creation of an anti down-quark
Figure 81 - Strange quark decay into anti down-quark
Decay processes
Down Antiquark Decay into Up Quark and W- Boson:
In this process, a down antiquark (anti-d) can change into an up quark (u) by emitting a W- boson (W-).
The W- boson is a mediator of the weak nuclear force, responsible for processes like beta decay. It's a very massive particle.
The down antiquark, being a more massive particle than the up quark, can transform into an up quark by exchanging energy and momentum with the W- boson.
This process is described by the weak interaction, and it's one way that down antiquarks can change into other types of quarks.
Charged pion decay
This decay is due to the weak interaction. The primary decay mode of a pion, is a leptonic decay into a muon and a muon neutrino:
Figure 82 - Antidown quark decay
Figure 83 - Charged pion decay
Annihilation
See down quark annihilation.
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