particle physics Flashcards
(26 cards)
what is beta minus decay?
when a neutron turns into a protron and emits an electron and an electron antineutrino.
by referring to the interaction between protrons, explain why a force is required to hold nucleons together in the nucleus
due to the eclectrostatic repulsions of protrons
the protrons (and neutrons) would not remain stable in the nucleus.
the strong nuclear force can sometimes be postitve an sometime be negative, what does this mean ?
positive=repulsive between nucleons
negative=attraction between nucleons
what is beta plus decay?
when a protron turns into a neutron and emits a positron and an electron neutrino
what is a similarity and a difference between a particle and its antiparticle?
same rest mass
different charges and quantum numbers
what does an annihilation reaction release and why?
releases two photons, they must go in opposite directions to conserve momentum
what is pair production?
A photon interacts with a nucleus, and its energy is converted into the mass of a particle and its corresponding antiparticle.
what are the four fundamental forces?
strong nuclear
weak nuclear
elcetromagnetic
gravity
what are exchange particles?
exchange particles are force carriers for the fundamental forces
what do exchange particles transfer?
energy, momentum, force and sometimes charge
what does the size of an exhange particle determine?
the size determines the range of the force; the bigger the parcle the shorter the range of the force
what is electron capture?
A protron captures an innershell electron and turns into a neutron, and electron neutrino. (A w+ boson is exchanged in the process).
what is electron protron collision?
A protron and electron collide and a w- boson particle is exchanged. The electron turns into an electron neutino, and the protron turns into a neutron.
how do hadrons interact and what are they made of?
hadrons interact by the strong nuclear force and are made of quarks
what are baryons made of and what do they decay into?
Baryons are made of 3 quarks (antibaryons 3 antiquarks) and all decay into a proton which is the only stable baryon. (the ones we need to know are protrons and neutrons).
what are mesons made of,and what do they include?
A quark and antiquark pair.
(They include pions which are the exchange particle in the strong nuclear force, and the heavier kaons which decay into pions.)
what are leptons?
fundamental particles that dont interact by the strong interaction, only the weak interaction.
electrons are stable leptons
muons are heavier elctrons which decay into electrons
neutrinos, the electron neutrino and a muon neutrino have no mass and no charge
how do you work out the baryon number?
0 except for bayons which are 1+
how do you work out strangeness?
k+ and k0 are +1, k- and anti k0 are -1
how are strange particles created?
through the strong interaction and in pairs. they decay through the weak interaction.
when is strangeness conserved?
strangeness is conserved by strong interaction but changes by 0 or +1, or -1 in weak interactions
what are isotopes?
atoms with the same number of protrons but different number of neutrons
what is the range of the strong nuclear force?
between 3-0.5fm is an attractive force.
Describe why the neutrino was hypothesised to account for the conservation of energy in beta decay
when they found electrons were emmited at various energies during beta decay Hence, the continuous range of energies was accounted for using this new particle, the neutrino
