Particle Physics - alpha scattering experiment, quarks Flashcards
What is the proton number?
Number of protons in the nucleus
What is the nucleon number?
Number of particles in the nucleus
Outline the rough history of the development of the nuclear model. (6 points)
- Started from a ball of charge
- Then onto negative charges spread throughout the sphere of positive charge, called electrons (yum pudding)
- Then we found that the majority of mass is concentrated in the centre, named the nucleus (alphar scattering)
- Then we found that the nucleus was positively charged (also alphar scattering)
- We found that the electrons travelled around the nucleus on different orbits called energy shells or energy levels
- Then we discovered that the nucleus also had neutrons
What were the outcomes and conclusions were made from the Alpha Scattering experiment by Rutherford?
- Only a very small amount of alpha deflected straight back (small concentrated mass in centre)
- Majority of alpha passed straight through the foil (most of the gold atoms were empty space)
- A lot of alpha deflected to the sides and the gold didn’t (mass of nucleus is much higher than the mass of alpha particles)
Why could they NOT conclude that the nucleus was positively charged from the Alpha Scattering experiment?
- Positively charged alpha deflected when it got close to the nucleus as they were both positive
- HOWEVER, negatively charged electrons would be equally attracted towards the nucleus if they got close
- IN CONCLUSION, the deflection patterns are exactly the same for negatively charged particles as to positive particles
What could we conclude about the nucleus in simple words? (3)
- Tiny
- Massive
- Charged
What are quarks?
- charged matter within a proton or a neutron
What are the three generations of quarks (their names, their sign and their charges)?
- Positive ones; Up (u), Charm (c), Top (t)
- Negative ones; Down (d), Strange (s), Bottom (b)
Charge of positive ones; 2/3 e
Charge of negative ones; -1/3 e
What is the quark composition of a proton?
- x2 ‘u’ quarks
- x1 ‘d’ quark
What charge does two top quarks and one strange quark result in?
2 (2/3 e) + 1 (-1/3 e) = -1 e = +1 charge
What is the quark composition of a neutron?
- x1 ‘u’ quark
- x2 ‘d’ quarks
What charge does having one charm quark and 2 bottom quarks result in?
1 (2/3 e) + 2 (-1/3 e) = 0 charge
Name the 6 leptons, their sign and their charges
- Generation 1: Electron (e^- // -e), Electron Neutrino (νe // 0)
- Generation 2: Muon (μ // -e), Muon Neutrino (νμ // 0)
- Generation 3: Tau (τ // -e), Tau Neutrino (ντ // 0)
What’s the general pattern of the masses of the quarks and leptons through the generations?
They get heavier
What is the thing that links together quarks?
Gluons
What two categories can particles be divided into and state the difference between these two types of particles?
Leptons and Hadrons
Leptons DON’T feel the nuclear force
Hadrons DO feel the nuclear force
What two further categories can Hadrons be divided into?
Mesons and Baryons
In the category of Hadrons, state the composition difference between Mesons and Baryons?
Mesons; 1 quark and 1 anti-quark
Baryons; 3 quarks or 3 anti-quarks
What is an anti-quark?
- Same mass (you cannot get a negative mass)
- Opposite physical properties (eg. positive charge instead of negative)
How does the sign change when it is an anti-quark?
There is a bar above the letter
Strangeness is …
… is how strange the particle is.
- If it has a ‘strange’ quark in the composition then its strangeness is -1.
- If it has an ‘antistrange’ quark in the composition then its strangeness is +1.
