Quarks and Leptons

Lepton number of leptons (electrons and electron neutrinos) ?

1

Lepton number of anti-leptons (positron and anti-neutrino)

-1

uuu baryon

symbol and charge

Δ⁺⁺

+2e

uud baryon

symbol and charge

p (proton)

+e

udd baryon

symbol and charge

n (neutron)

0

ddd baryon

symbol and charge

Δ^-

-e

What baryon number do baryons have?

1

Which baryons decay the quickest?

uuu and ddd

What do uuu and ddd baryons decay into

uud and udd

What charges and numbers do anti-particles have compared to normal particles?

opposite (e.g. 1 → -1)

uƌ pion

symbol and charge

∏⁺

+e

ūd pion

symbol and charge

∏^-

-e

ūu pion

symbol and charge

∏⁰

0

dƌ pion

symbol and charge

∏⁰

0

which are the shortest lived pions and why?

ūu and dƌ

because they annihilate each other as soon as they are formed

which pions are anti-particles of each other?

uƌ and ūd

Four forces/interactions experienced by particles

Gravitational (negligable)

Weak

EM

Strong

Conditions for weak force (3)

• neutrinos

• change in flavour

• long lifetime ＞10^-12

Conditions for strong force (2)

• only quarks/hadrons involved

• short lifetime ∼10^-24

Conditions for EM force (2)

• photons involved

• medium lifetime ∼10¹⁸

Photon symbol, baryon number, lepton number and charge

ɣ, 0, 0, 0

What force is neutron decay governed by?

weak (neutrino involved, long lifetime and change in flavour)

n → p + e + anti-neutrino

What force is proton-proton collision governed by?

strong (all particles hadrons)

p + p → p + p + ∏⁰

What force is proton-proton fusion governed by?

weak (neutrino present)

p + p → ²₁ H + e⁺ + v_e

(process that happens in the sun)

What force is ∏^- decay governed by?

weak (neutrino present, flavour change)

∏^- → e + anti- neutrino

What force is ∏⁺ decay governed by?

weak (neutrino present, flavour change)

∏⁺ → e⁺ + v_e

What force is ∏⁰ decay governed by?

EM (photons present)

∏⁰ → ɣ + ɣ (decays to 2 photons)

What force is Δ governed by?

strong (only hadrons involved)