Chapter 1: Particle Physics

Question 1

What particles can interact via the weak force?

Answer 1

all hadrons (all quarks) and all leptons too

Question 2

Which particles can interact with the strong force?

Answer 2

all quarks (all hadrons)
only hadrons experience the strong force

Question 3

What particles interact with the electromagnetic force?

Answer 3

all charged particles

Question 4

How are forces exerted between objects?

Answer 4

forces between objects are exerted by the exchange of virtual particles and bosons (exchange particles)

Question 5

What is particle decay?

If no work is done into a system, what will the particles tend to do?

Answer 5

when exotic, heavier particles change to smaller more stable particles
if no work is done into a system, the particles will tend back to more stable particles

Question 6

What must always be assumed is conserved in particle interactions?

Answer 6

energy/mass

momentum

Question 7

What must be proven to be conserved in particle interactions in an exam?

Answer 7

charge
baryon number
lepton number

Question 8

How fast is the decay via strong force?

Answer 8

fast decay via the strong force

Question 9

How fast is the decay via the weak force?

Answer 9

slow decay via the weak force

Question 10

How must strange particles be produced?

Answer 10

strange particles must be produced in pairs

Question 11

How are strange particles produced?

Answer 11

via the strong force

Question 12

When is strangeness conserved and when is it not conserved?

Answer 12

strangeness must be conserved in decays via the STRONG force

strangeness doesn’t have to be conserved in weak interactions- can change by +1, -1 or it can be conserved (0)

Question 13

What is an example of a strange particle and why is it strange?

Answer 13

Kaon
they are big particles but take a long to time to decay compared to their mass and they do not conserve strangeness so it can only decay via the weak interaction

Question 14

How do strange particles decay?

Answer 14

via the weak interaction

Question 15

Why is strangeness not conserved in weak interactions?

Answer 15

because weak forces cause quarks to change type so it can cause strange quarks to change into a different type of quark ∴ strangeness is not conserved

Question 16

What causes particles to be strange?

Answer 16

a strange quark causes all this strange behaviour

Question 17

What are the 6 main properties of particles?

Answer 17

energy-mass
charge
spin
strangeness
lepton number
baryon number

Question 18

What is one MeV in joules?

Answer 18

1 MeV = 1.60 x 10⁻¹³J

Question 19

What is one atomic mass unit?

Answer 19

it is approximately the mass of one nucleon (either a single proton/neutron)

Question 20

What is specific charge and its units?

Answer 20

it is the charge to mass ratio
specific charge= Ckg⁻¹
it influences particle behaviour

Question 21

What is dependent on the value of specific charge?

Answer 21

specific charge influences how much a particle is deflected when it is in an electric/magnetic field
greater specific charge—- more the particle is deflected
smaller specific charge—- less the particle is deflected
no specific charge —- no deflection

Question 22

What is the specific charge of an Mg 2+ ion?

Answer 22

2 * 1.60 *10 ⁻¹⁹ charge
24 * 1.67 * 10⁻²⁷ mass
charge/mass == 7.98 *10⁶ Ckg⁻¹

Question 23

How does the specific charge of an ion compare to the specific charge of a particle?

Answer 23

specific charge of an ion is much smaller than that of a particle
this is because neutrons are in ions which add to the mass but not the charge