Particles Flashcards
What are Isotopes, and what can they lead to?
They are the same element with different number of neutrons this could cause instability and hence decay.
Within what range is the strong force attractive?
0.5 fm - 3 fm (f = ×10^-15)
What forces act on the nucleus of an atom?
electromagnetic force will push the particles away from each other (the same charge will oppose each other). They are held together mainly by the strong nuclear force and partly by gravity.
What are the two categories of particle?
Hadrons and Leptons
Which type of particle experiences the strong force?
Hadrons (Baryons and mesons)
Which type of particle is found outside of the nucleus?
Leptons (electrons, muons etc)
What are mesons made of?
One quark and one antiquark
What are baryons made of?
Three quarks
Which particle contains at least one strange quark?
Kaon
Are leptons made of quarks?
No, only hadrons are.
What makes an anti particle different to a regular particle?
They have the same mass, opposite charge, opposite lepton and baryon number.
What are the properties that are necessary for the strong interaction?
Particles: Hadrons only
Exchange particles: Pion or Gluon
Strangeness: must be conserved
Example:
p + n —> p + n + (pion)^0
What are the properties that are necessary for the weak interaction?
Particles: Hadrons and Leptons or Hadron decay
Exchange particle: W plus or minus boson
Strangeness: does not have to be conserved
Example:
n —> p + e^- + (anti neutrino)
Why is there a neutrino added in a weak interaction?
This occurs in order to keep an equal lepton number.
Why is strangeness only conserved in the strong interaction?
Scientists discovered that when kaons interact in the nucleus, they do not decay, this thus shows that something must be conserved within this interaction (strong interaction). It is strangeness that is conserved.
However, when removed from the nucleus, they do decay. This shows that under the weak interaction, the kaons don’t have to conserve strangeness (they still can though).
What are the properties of an electromagnetic interaction?
Particles: Charged
Exchange particle: Virtual photon
Strangeness: must be conserved
Example:
p +p —> p + p
What are the properties of alpha decay?
It is the most ionising (it has the most mass)
Least penetrative, it can be stopped by paper (this is because it is too big to get through anything)
= 2protons, 2neutrons
4
X
2
What are the properties of beta decay?
Medium ionising and penetrative ability, it can be stopped by a few cm of aluminum.
It can also be shown as an electron.
0
B
-1
What does ionising mean?
The ability to gain or loose an electron.
How do you calculate the charge of an exchange particle?
The charge of the input particle = charge of output particle + charge of exchange particle.
Specific charge equation
SC = charge/mass
in an ion the charge will be the number of electrons added/removed * (1.6*10^-19)
In a nucleus, the charge is the total charge of the protons.
The mass is always of the nucleons (protons and neutrons).
Why does the exchange particle act on an angled line on the Feynmann diagrams?
Because the y axis is time and there is a change in time as the energy is transferred.
