An antiquark is a fundamental particle that makes up most of the mass in the antimatter. Each antiquark has an electrical charge, a baryon number, and a strange number. The symbol of an antiquark is q. Antiquarks make antimatter, with some antimatter particles being produced during events called pair creation. Antiquarks can also compose particles with a mixture of particles and antiparticles.
Antiquarks and baryon numbers
The baryon number indicates if you have a particle or an antiparticle. See the following table showing the negative quarks that make up antimatter.
| Table 1. Negative quarks: symbols, electrical charge, Baryon numbers, strange numbers. |
|---|
| Particle | Symbol | Electrical charge | Baryon number | Strange number |
| Anti up | \(\bar{u}\) | -⅔ | -⅓ | 0 |
| Anti down | \(\bar{d}\) | + ⅓ | -⅓ | 0 |
| Anti strange | \(\bar{s}\) | + ⅓ | -⅓ | +1 |
| Anti charm | \(\bar{c}\) | -⅔ | -⅓ | 0 |
| Anti top | \(\bar{t}\) | -⅔ | -⅓ | 0 |
| Anti bottom | \(\bar{b}\) | + ⅓ | -⅓ | 0 |
Antimatter and pair creation
The creation of antimatter occurs in the pair creation process. This happens when matter collides with a high-energy photon. The collision emits two particles, one made of matter, while the other is the antiparticle.
Figure 1. A high-energy photon collides with a nucleus, producing a positron and an electron. This also creates a particle-antiparticle pair. Source: Manuel R. Camacho, StudySmarter.
Antimatter quark composition
Antiquarks make up antimatter. They are the particles that make up antiprotons and antineutrons, which contain three antiquarks. Their symbol is as follows:
\[\text{Antimatter quark symbol} = \overline {qqq}\]
The composition of antiprotons and antineutrons is as follows:
Antiproton
As this has a charge of -1, the combined charge of the antiquarks that compose the antiproton must be -1. This requires two anti-up quarks and one anti-down quark.
\[\text{antiproton} = \overline{udu}\]
The antiproton charge is determined by the addition of the three antiquarks.
\[\text{antiproton charge} = -\frac{2}{3} + \frac{1}{3} -\frac{2}{3} = -1\]
The charge value indicates that you are dealing with an antiproton. Antiprotons and antineutrons can be classified as baryons, which consist of antiquarks with a baryon value of -1. See the following addition of the baryon numbers for the antiproton.
\[\text{antiproton} = -\frac{1}{3} -\frac{1}{3} -\frac{1}{3} = -1\]
A baryon number of -1 indicates that you are dealing with a baryon made up of antimatter.
Antineutron
As this has a charge of 0, the combined charge of the antiquarks must be zero. This requires two anti-down quarks and one anti-up quark.
\[\text{antineutron} = \overline{dud}\]
The addition of the charges of the three antiquarks is as follows:
\[\text{antineutron charge} = \frac{1}{3} - \frac{2}{3} + \frac{1}{3} = 0\]
The total charge indicates that you are dealing with an antineutron. Adding the antineutron’s baryon numbers must give you a value of -1.
\[\text{antineutron} = -\frac{1}{3} - \frac{1}{3} -\frac{1}{3} = -1\]
A baryon number of -1 indicates that you are dealing with a baryon made up of antimatter.
Figure 2. A proton and an antiproton’s quark composition. The antiproton has the same mass but a negative charge. Source: Manuel R. Camacho, StudySmarter.
Pion minus and kaon minus hadrons
Quarks can combine with antiquarks, creating a matter-antimatter duo. The pion minus and the kaon minus hadrons are two examples. The pion minus and the kaon minus are the results of the combination of an anti-up and a down quark.
- Pion minus: a combination of an anti-up quark with a charge of -⅔ and a down quark with a charge of -⅓ and thus a total charge of -1.
- Kaon minus: a combination of an anti-up quark with a charge of -⅔ and a strange quark with a charge of - ⅓ and thus a total charge of -1.
The pion plus and the kaon plus quarks have a baryon number of 0, indicating that they are a combination of matter and antimatter.
Antiquark - Key takeaways
- Antimatter consists of antiparticles such as antiquarks, which compose the antineutrons and antiprotons.
- Antiquarks have a charge value of -⅔ or + ⅓.
- A combination of three antiquarks composes an antineutron or an antiproton. Their respective charge is 0 or -1.
- There are also particles with a negative charge composed of quarks and antiquarks, which are called pion minus and kaon minus.
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