Particles Flashcards
What forces are acting with in a nucleus?
Gravity - attracting nucleons together because of there mass.
Electromagnetic - causes + charged protons to repel.
Strong nuclear force - mostly attractive but repels at very small distances.
What are the abbreviations for
Proton number
Nucleon number ?
Proton number - z
Nucleon number - A
Describe the strong force
A very short range
Repels from less then 9.5 fm
Attracts up to around 3 fm
How many netter is 1 fm?
1x10^-15 m
At what distance does the strong force prevent particle colliding?
0.5 fm
What is nuclear decay?
When an unstable nuclei emits particles to scone more stable.
Why are some nucleases unstable?
The strong force has only a small range so large nucleases struggle to stay together. (Alpha decay)
Or
There is a very uneven proton to neutron count. They are neutron rich. (Beta - decay)
When would beta decay happen
When a nucleus is too neutron rich
When would alpha decay happen?
When a nucleus is too large to be kept stable by the strong force.
What happens in alpha decay?
A large nucleus of 82 protons or more emits an alpha particle (a helium nucleus decreasing the protons by 2 and nucleon number by 4.
What happens in beta minus decay?
An neutron turns into a print emitting an electron and antineutrino to account for some of the energy. The nucleon number stays the same but the proton number increases.
For every particle there is a corresponding …
Antiparticle. Eg electron and positron.
What is the frequency of a wave?
The the number of complete oscillations of a wave passing a point per second.
What is a waves wavelength?
The distance in meters between two adjacent crests.
What is pair production is when…
When there is enough energy to create matter a particle and anti particle are produced.
How do you work out the minimum energy for a pair production?
It is 2 x the rest energies
Min E = 2E0
What happens when a particle meets its antiparticle?
Annihilation, all the mass is converted back into energy in the form of 2 gamma rays.
What is the minimum energy of one and both of the photons produced by annihilation?
1 photon min E = rest mass
Both photon min E = 2xrest mass
Particles that feel the strong force are called …
Hadrons
What is the only stable baryon?
A proton so all baryons decay to it.
Baryon number is conserved but what is the baryon number for an antiproton?
-1
What is neutron decay also known as?
Beta decay
What interaction is responsible for neutron decay/ beta decay ?
The weak force
What pions gory do pions fit under?
Meson
Discribe mesons
They are unstable
Have a baryon number 0
They interact with hadrons through the strong force.
Name 2 mesons
Kaon and pion (the lightest)
What forces do leptons feel?
Weak interactions, electromagnetic (if charged) and gravity.
What category are pions, where are they found, what do they do
Mesons, comic rays or high energy collisions, they are involved in the change of neutron to proton and protons into neutrons.
What is the lightest meson?
A kaon or a pion?
Name the 3 types.
Pion
Pi +
Pi -
Pi 0
Name the 3 types of kaons and what category are yet classes under?
K+
K -
K 0
Name the 4 real leptons needed for the AS.
Electron
Muon
Electron neutrino
Muon neutrino
What charge does a muon have and what category is it classed under?
Muon = U- A negative charge
It is a lepton.
What is the lepton number for an antimuon neutrino
-1
What do you need to remember when calculating the lepton number?
That the electron and muon numbers are calculated separately.
What are the types of muons?
U- (real)
U + (anti)
What is the quark structure of a proton?
UUD
What is the quark structure of a neutron?
UDD
What is the quark structure of mesons?
A quark and an antiquark
What is the quark structure of baryons?
3 quarks, qqq
What properties of quarks are passed on to the particle they make?
Charge
Strangeness
Baryon number
What is the quark structure do an antineutron?
Anti u , anti d, anti d
What is the quark structure that make up a pion.
A quark and antiquark
Consisting of only up, down, anti up or anti down quarks.
_
1 exception of ss a pi0 pion.
What is the quark structure of a kaon?
A quark and an antiquark
Must have one strange or anti strange.
What are the 3 ways of making a pi 0 pion?
UU , DD, SS
What property does kaons have that pions don’t
Strangeness
What happens when you try to remove a quark?
The energy used undergoes pair production to make a meson.
And the original quark stays as part of a particle due to quark confinement.
What is meant by quark confinement.
That is is impossible to isolate a quark by itself.
A quark turning into another quark is known as
Changing the quark’s character
Describe beta plus decay
A proton turns to a neutron It happens in isotopes with too few neutrons e.g carbon-11 A positron and neutrino are created. A U quark changes to a D quark UUD > UDD
In terms of quarks what happens with beta minus decay?
UDD > UUD. Neutron to proton
A d quark changes to a u quark.
What is the equation for beta + decay?
P–> n + (e+) + (Ve)
Via weak interaction
What properties are conserved in all particle reactions?
Lepton number, Baryon number, charge
What property is only conserved with strong force reactions?
Strangeness
Examples of conservation of charge and baryon number.
Pair production
Beta minus decay
Beta plus decay
