Physics - Standard Model

Created: January 31, 2022

Flashcards

2022-01-31

What are the four fundamental forces?
  1. Strong nuclear force
  2. Weak nuclear force
  3. Electromagnetic force
  4. Gravitational force

In what context does the strong nuclear force show up?

Holding nucleons together.

When does the electromagnetic force act?

When two charged objects interact.

In what context does the weak nuclear force show up?

Beta decay.

When does the gravitational force show?

When any particles have mass.

What is the relative strength of the strong nuclear force?
\[1\]

What is the relative strength of the electromagnetic force?
\[10^{-3}\]

What is the relative strength of the weak nuclear force?
\[10^{-6}\]

What is the relative strength of the gravitational force?
\[10^{-40}\]

What is the range of the strong nuclear force?
\[\approx 3 \text{fm}\]

What is the range of the electromagnetic force?
\[\infty\]

What is the range of the weak nuclear force?
\[\approx 1 \text{fm}\]

What is the range of the gravitational force?
\[\infty\]

Which of the 4 fundamental forces is the weakest?

Gravity.

When is the strong nuclear force attractive?

Between $3 \text{fm}$ and $0.5\text{fm}$.

When is the strong nuclear force repulsive?

At distances less than $0.5\text{fm}$.

2022-02-03

What, according to the Standard Model, comes with every type of particle?

A corresponding antiparticle.

What is the name of an electron’s antiparticle?

A positron.

What two things are true about a particle’s corresponding antiparticle?
  • Same mass
  • Opposite charge

If a proton is denoted $p$, how would you denote an antiproton?
\[\bar{p}\]

What, in terms of quarks, are the antiparticle versions of hadrons made from?

Antiquarks.

What is a fundamental particle?

A particle that has no internal structure and so cannot be divided into smaller particles.

What is an example of a fundamental particle?
  • Electron
  • Neutrino
  • Muon

What is the process where a particle and an antiparticle are mutually destroyed called?

Annihilation.

Why isn’t a proton or a neutron a fundamental particle?

Because they can be divided into quarks.

What are the two broad categories of particles in the standard model?
  1. Leptons
  2. Hadrons

What is “lepton” Greek for?

“Light”, because the particles are light.

How can you remember that hadrons have mass?

Think “the large hadron collider”, it has to shove things with mass into one another.

What are the 6 leptons?
  1. Electron
  2. Muons
  3. Tau
  4. Electron neutrinos
  5. Muon neutrinos
  6. Tau neutrinos

What is a lepton?

A fundamental particle that does not experience the strong nuclear force.

What is a hadron?

A non-fundamental particle that do experience the strong nuclear force and decay via the weak nuclear force.

What are all hadrons made from?

Quarks.

What are the two sub-categories of hadrons?
  1. Baryons
  2. Mesons

In terms of the sub-categories of hadrons, what is most of ordinary matter made from?

Baryons.

In terms of the sub-categories of hadrons, which consist of three quarks?

Baryons.

In terms of the sub-categories of hadrons, which consist of quark-antiquark pair?

Mesons.

What is true about the quark-antiquark pair in a meson?

The quarks are not of the same type, otherwise they’d annihilate one another.

What are the six quarks?
  1. Up
  2. Charm
  3. Top
  4. Down
  5. Bottom
  6. Strange

What is the charge of the up, charm and top quarks?
\[+2/3 e\]

What is the charge of the down, strange and bottom quarks?
\[-1/3 e\]

What combinations of quarks makes a proton?
\[u, u, d\]

What combination of quarks makes a neutron?
\[d, d, u\]

How can you work out the overall charge of a particle from its quarks?

Add them together.

What combination of quarks makes an electron?

Trick question – electrons are not made of quarks.

What combination of quarks makes an antiproton?
\[\bar{u}, \bar{u}, \bar{d}\]


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