Chapter 2: Fundamental Particles

Question 1

What are antiparticles?

Answer 1

Fundamental particles with the same mass and energy as their corresponding particles but opposite charge and conservation numbers

Question 2

What are quarks?

Answer 2

Fundamental particles that make up hadrons (eg baryons and mesons). They exert the strong nuclear force on one another.

Question 3

What are gluons?

Answer 3

One of the four exchange particles responsible for the nuclear strong force. They act between quarks holding them together and have a very short range.

Question 4

What are exchange particles?

Answer 4

Particles involved in the interaction of particles via the four fundamental forces of nature on the quantum scale. They are created, emitted, absorbed and destroyed between the interacting particles.

Question 5

What is the exchange particle for electromagnetic force?

Answer 5

Virtual photons
Acts between charged particles

Question 6

What is the exchange particle for the strong nuclear force?

Answer 6

Gluons
Acts between quarks

Question 7

What is the exchange particle for the weak nuclear force?

Answer 7

W+, W- Z 0 bosons
Responsible for radioactive decay (not alpha) and nuclear fusion

Question 8

What is the weak force?

Answer 8

A force a million times weaker than the strong force and acting over a shorter range. It is responsible for beta decay, electron capture and electron-proton collision.

Question 9

What are leptons?

Answer 9

Fundamental particles that do not feel the strong force (as they are not made of quarks). Includes electron, muons, neutrinos, tauons.

Question 10

What are hadrons?

Answer 10

Subatomic particles that are made of quarks so feel the strong force. Include baryons and mesons.

Question 11

What are baryons?

Answer 11

A class of hadron that are made of three quarks. The only stable baryon is the proton. Includes protons and neutrons.

Question 12

What are mesons?

Answer 12

A class of hadron that is made of a quark and antiquark pair. Includes pions, kaons.

Question 13

What is lepton number?

Answer 13

A quantum number that is conserved in all particle interactions. Both electron lepton numbers and muon lepton numbers must be conserved.

Question 14

What particles have a lepton number of 1?

Answer 14

Electron lepton number: electrons, electron neutrino
Muon lepton number: muons, muon neutrino

Question 15

What is a muon?

Answer 15

A heavy electron (x200 the mass). It decays into an electron (or positron) and two neutrinos.

Question 16

What are the quark compositions of protons and neutrons (and their anti particles)?

Answer 16

Proton: uud
Neutron: udd
Antiproton: ūūð
Antineutron: ūðð

Question 17

What are the quark compositions of the pions?

Answer 17

π+ : uð
π- : dū
π° : uū or dð

Question 18

What are the quark compositions of the kaons?

Answer 18

K+ : uš
K- : sū
K° : dš

Question 19

What is baryon number, B?

Answer 19

A quantum number that is conserved in all particle interactions. Baryons have a baryon number of +1, anti-baryons have a baryon number of -1 and non-baryons have a baryon number of 0.

Question 20

What baryon numbers do quarks and antiquarks have?

Answer 20

Quarks: +1/3
Antiquarks: -1/3

Question 21

What is strangeness?

Answer 21

​A quantum number that is conserved in strong interactions but not in weak interactions. This reflects that strange particles are always produced in pairs. Strange quarks have a strangeness of -1.

Question 22

What are strange particles?

Answer 22

Particles that are produced through the strong interaction but decay through the weak interaction.

Question 23

What quantities are always conserved?

Answer 23

Charge
Mass-energy
Momentum
Lepton numbers
Baryon number

Question 24

What quantity is not always conserved in the weak interaction?

Answer 24

Strangeness. Can change by -1, 0 or +1.