1.7 Particles and nuclear structure Flashcards
What is an antiparticle?
An antiparticle has the same properties as its equivalent particle (e.g. the same mass), except it has opposite charge.
How do you recognise the symbol for an anti particle?
the symbol for an antiparticle includes a bar above the symbol
What are all leptons/antileptons and their charges?
Leptons
- electron -1
- electron neutrino 0
Antileptons
- antielectron/positron +1
- Electron antineutrino 0
What are all quarks/antiquarks and their charges?
Quarks
- Up +2/3
- Down -1/3
Anti quarks
- Antiup -2/3
- Antidown +1/3
What is annihilation?
When a particle and its antiparticle meet, they annihilate each other. This means when a particle encounters its antiparticle (e.g. an electron and a positron), all the mass is converted into energy.
What are leptons?
Leptons are the lightest of the subatomic particles and they always exist separately. They do not combine to form composite subatomic particles.
What are hadrons?
Unlike leptons, quarks and antiquarks do not exist separately and combine to form composite subatomic particles known as hadrons.
What are the three types of hadrons and their composition?
- baryons – consists of 3 quarks -proton/neutron
- antibaryons – consists of 3 antiquarks -antiproton/antineutron
- mesons – consists of 1 quark-antiquark pair. - pions
All quarks have baryon number = +⅓, and all antiquarks have baryon number = -⅓. This means that all baryons must have baryon number = 1 and antibaryons = - 1.
What is the charge, baryon number and quark composition of a proton?
Charge +1
Baryon number +1
quark composition uud
What is the charge, baryon number and quark composition of a neutron?
Charge 0
Baryon number +1
quark composition udd
What are the four pions and their composition?
Mesons consist of one quark and one antiquark, as a result they have a baryon number of 0
The first generation quarks and antiquarks combine to form the pions:
π+ ud- 1e
π- -ud 1e
π0 uu- 0e
π0 dd- 0e
What is the conservation of charge law?
When charge is conserved through a reaction. It will be the same on one side of the equation as the other.
What are the four fundamental forces?
Gravitational
electromagnetic
weak
strong
What are the properties of gravitational force?
Experienced by - All matter
Range - infinite
Comments - very weak – negligible except between large objects such as planets
What are the properties of weak force?
Experienced by - all leptons, all quarks
Range - very short
Comments - only significant when the e-m and strong interactions do not operate
What are the properties of electromagnetic force?
Experienced by - all charged particles
Range - infinite
Comments - also experienced by neutral hadrons, as these are composed of quarks
What are the properties of strong force?
Experienced by - all quarks
Range - short
What are strong interactions?
Strong interactions (lifetime 10^-24s)
- Only hadrons are involved.
- There is no change in quark flavour.
- These are typically involved in collisions between particles.
What are electromagnetic reactions?
Electromagnetic interactions (lifetime 10^-12-10^-18 s)
- The particles must be charged or have charged components. Although a neutron is uncharged, it consists of charged quarks.
- There is no change in quark flavour.
- One or more photons may be emitted.
What are weak interactions?
Weak interactions (lifetime 10^-8 s)
- Neutral leptons (neutrinos) are involved.
- There may be a change in quark flavor.
