Particle Physics Flashcards
What is concerved in a nuclear reaction?
Mass-Energy is conserved
Momentum is conserved
Electric charge is conserved
Disintegration energy
The energy released when a radioactive disintegration takes place spontaneously.
What is radioactive decay
Radioactive Decay is the disintegration of an unstable nucleus with the emission of one or more types of radiation.
What is the structure of an alpha particle?
An alpha-particle is a helium nucleus, i.e. a bundle of two protons and two neutrons, emitted from the nucleus of a radioactive atom.
Example of an alpha particle emitter
238
U is an alpha-particle emitter.
92
What is the nature of a beta particle
A beta-particle is a high-speed electron emitted from the nucleus of a radioactive atom.
Example of a beta particle emitte
14
Carbon-14. C
6
Beta decay changes the values how?
When an electron or beta particle is emitted from an element, the atomic number increases by one and the mass number stays the same
When a nucleus undergoes beta decay it appeared that
momentum was not conserved.
How did Fermi’s theory of radioactive decay resolve this?
It proposed the existence of another particle, called the neutrino, ν, that had the missing momentum.
Who and when
Proposed the existence of the neutrino?
Detected it?
The existence of the Neutrino was proposed in 1930 by Wolfgang Pauli, but it was not detected until 1956 by Cowan and Reines.
Give two reasons why it is difficult to detect a neutrino?
The Neutrino:
is uncharged
has a very small mass
& interacts weakly with matter.
Each particle has its own anti-particle. What is an Anti-Particle?
The Anti-Particle of a given particle has the same mass as the given particle, and its charge is equal but with opposite sign
Compare the properties of the Electron with those of its anti-particle, the Positron.
The electron and the positron have the same mass. The electron and positron have the same size electric
charge.
The electron has negative charge; the positron has positive charge.
An electron is matter; a positron is anti-matter. The electron and positron have opposite spin.
What is anti-matter
Anti-Matter is material or matter made up of anti- particles of the particles out of which normal matter is made.
The anti-particles have the same mass and a charge of equal size but opposite sign to their corresponding particles.
What is meant by pair production
Pair production is the creating of a particle and its anti- particle from electromagnetic energy (gamma rays).
In an accelerator two protons are accelerated to very high speed (i.e. very high kinetic energy) and made to collide with each other.
What reaction occurs?
The kinetic energy of the protons is converted into matter in the form of other particles.
In an accelerator two protons are accelerated to very high speed (i.e. very high kinetic energy) and made to collide with each other.
Write an equation showing this reaction.
p + p + energy → p + p + additional particles
In an accelerator two protons are accelerated to very high speed (i.e. very high kinetic energy) and made to collide with each other.
What happens if the kinetic energy of the colliding protons is increased?
More particles and particles of greater masses are produced.
Particles are classified according to whether they feel the Strong Nuclear Force or not. There are thus two families of particles. Name them.
The Leptons and the Hadrons.
What is a Lepton?
A Lepton is an elementary particle that does not feel the Strong Nuclear Force.
A Lepton feels:
the Weak Nuclear Force,
the Gravitational Force
and if it is charged, the Electromagnetic Force.
What is a Hadron?
A Hadron is a particle that does feel the Strong Nuclear Force.
A Hadron feels:
the Strong Nuclear Force the Weak Nuclear Force,
the Gravitational Force
and if it is charged the Electromagnetic Force.
What is an Elementary Particle?
An Elementary Particle is a particle that is not made up of other particles and has no internal
structure.
Leptons are Elementary Particles.
Hadrons are not elementary particles.
Hadrons are not elementary particles.
What are they made up of?
Hadrons are made up of elementary particles
called Quarks and Antiquarks.
Hadrons are divided into two families, called the Baryons and the Mesons.
What are Mesons?
Mesons are hadrons that have masses between that of the electron and the proton.
What are Baryons?
Baryons are hadrons that have masses greater than or equal to that of the proton.
What are Quarks?
Quarks (and Anti-Quarks) are Elementary Particles out of which hadrons (i.e. baryons and mesons) are made.
Quarks have an electric charge of: +/- 1/3 e or +/- 2/3e
Name the six flavours of quark?
Up, Down
Strange, Charmed
Top, Bottom
What is the quark composition of a Baryon?
A Baryon is made up of any three quarks (or any three anti-quarks)
What is the quark composition of a proton?
A proton consists of two up quarks and a down quark. Protons are baryons.
What is the quark composition of a Meson?
A Meson is made up of any one quark and any one anti-quark
Name three negatively charged quarks and their charges.
Down. -1/3e
Strange -1/3e
Bottom. -1/3e
Name three positively charged particles and their charge
Up. +2/3 e
Charmed +2/3 e
Top. +2/3 e
