chapter 2.3-2.4 - quarks and leptons

what can leptons and antileptons interact to produce

hadrons

an electron-positron annihilation event

produces a quark and a corresponding antiquark, which move away in opposite directions, producing a shower of hadrons in each direction

through what interactions can leptons change into other leptons

weak interaction

what occurs in an interaction between a lepton and a hadron

a neutrino or an antineutrino can change into or form a corresponding charged lepton - has a lepton number of +1 before change and +1 after change, so is permitted

what occurs in muon decay

the muon changes into a muon neutrino; + an electron is created to conserve charge; + a corresponding antineutrino is created to conserve lepton number

lepton numbers for leptons, antileptons, and a non-leptons

lepton = +1, antilepton = -1, non-leptons = 0

what interactions do strange particles decay through

the weak interaction

strangeness in a strong interaction vs in a weak interaction

strangeness is always conserved in a strong interaction, whereas strangeness can change by 0, +1, or -1 in a weak interaction

the name of strange particles that decay into pions

kaons

how sigma particles decay

either in sequence, or directly into protons + pions

mesons

hadrons, made up of quark + antiquark pairs - will have a baryon number of 0

why won't a quark + antiquark pair annihilate each other

they are mediated by the strong force, which is repulsive at small distances

strangeness of pions

0

baryons and antibaryons

hadrons that consist of 3 quarks for a baryon, or 3 antiquarks for an antibaryon

combination of quarks for a proton

uud

combination of quarks for a neutron

udd

combination of quarks for an antiproton

anti-up, anti-up, anti-down

the sigma particle

a baryon containing a strange particle

what is the only stable baryon

the proton

what change happens to the quarks in beta- decay

a down quark changed to an up quark (a neutron changes into a proton in beta- decay)

what change happens to the quarks in beta+ decay

an up quark changes to a down quark (a proton changes into a neutron in beta+ decay)