1.7 particles and nuclear structure

Hadrons

made up of quarks

Baryons

made of three quarks

Mesons

an quark and antiquark

quark baryon number

+1/3

antiquark baryon number

-1/3

antiparticles

Each antiparticle has the same properties as its equivalent particle except opposite charge.

lepton number

all leptons have a lepton number of +1

antilepton number

-1

proton quark composition

uud

neutron quark composition

udd

conservations laws

• Conservation of charge.

• Conservation of baryon number.

• Conservation of lepton number.

Strong force

(lifetime 10-24s)

• Only involve hadrons.

• No change in quark flavour, (the same number of u and d quarks before and after).

• short lifetime.

electromagnetic force

(lifetime 10-12-10-18 s)

• The particles must be charged or have charged components.

• No change in quark flavour.

• One or more photons (gamma) may be emitted.

weak force

(lifetime 10-10 s)-long

• all particles feel it

•change in quark flavour.

• if neutrinos are involved it is weak