C24 (Partcile Physics) Flashcards
Observations and Conclusions from Alpha particle experiment:
Most alpha particles passed straight through thin gold foil, very little scattering, meaning most of atom made empty space, most mass conc at centre in small region called the nucleus.
-Very few positive alpha particles were repelled when in close proximity to the nucleus, meaning nucleus has positive charge, in fact charge on nucleus is quantised (1.6 x 10^-19).
Rutherford used alpha particles of KE 1.2 x 10^12J, with the idea of conservation of energy to calc the distance of the closest approach between an alpha particle and the gold nucleus.
The initial KE of alpha particle equal to what?
The initial KE of alpha particle = electrical potential energy at distance d
Term nucleon refers to what
Term nucleon refers either proton or neutron.
What’s the nucleon no. made up off
both protons and neutrons
Isotopes
are nuclei of same element, have same no. protons but different no. neutron.
Atomic Mass Units:
the masses of atoms and nuclear particles are often expressed in atomic mass units (u). The experimental value of 1u about 1.661 x 10^-27kg.
Radius of nucleus given by:
R= r0 x cube root of A
-(where r0 = 1.2 femto metres (1fm = 1.0^-15m))
-The simplest nucleus, hydrogen, has A value of 1.
-The approximate mass of particle is its nucleon no. in atomic mass units.
-A the nucleon no. (protons and nucleons)
What are the 3 forces within the nucleus
-The force acting between 2 point charges given by Coulomb’s law
-The force of gravity acting between 2 point masses, given by Newton’s law of Gravitation
-Strong nuclear force
Nature of the Strong Nuclear Force
-According to Coulomb’s law, there’s extremely large repulsive force, and gravitational force between protons, not strong enough hold together. Other force that aids is the strong nuclear force.
-This force acts between all nucleons (a very short range force).
Antimatter (Antiparticles):
-Every particle has corresponding antiparticle (if meet, destroy each other process annihilation, where their masses converted a high-energy pair of photons). Antiparticles have opposite charge to the particle and same rest mass.
What’s the antiparticle of an electron
-Antiparticle of electron is positron (same mass, opposite charge).
What are some other antiparticles (other then positron)
-Antiproton, Antineutron, Antineutrino
How are antiparticles normally symbolised?
antiparticles symbolised by bar over the letter of original particle.
What do fundamental forces explain?
These forces explain all known interactions.
What is weaker nuclear force responsible for inducing?
The weak nuclear force is responsible for inducing beta-decay within unstable nuclei.
What experiences strong nuclear force?
Experienced by nucleons
What experiences electromagnetic force?
Experienced by static and moving charged particles
Whats a result of weak nuclear force?
Responsible for beta-decay
What experiences gravitational force?
Experienced by all particles with mass
What’s the range for Fundamental forces
Electromagnetic and gravitational are infinite
Strong nuclear (10^-15m)
Weak nuclear (10^-18m)
What’s a fundamental particles
A particle that has no internal structure, hence cannot be divided into smaller bits (quarks,electrons and neutrinos).
What type categories are subatomic particles split into?
Hadrons and Leptons
Hadrons
particles and antiparticles, affected by strong nuclear force (e.g protons, neutrons, and mesons). If charged, also experience electromagnetic force. Hadrons decay by weak nuclear force.
Leptons
particles and antiparticles, not affected by strong nuclear force (e.g electrons, neutrinos, and muons). If charged, also experience the electromagnetic force.
The CERN announced what?
CERN announced discovery of Higgs Boson (explaining why all particles have the property of mass).
List the 2 fundamental particles that aren’t made of quarks
Fundamental particles, not made of quarks (e.g electron, neutrinos).
Leptons examples
electrons, neutrinos, muons
Hadrons examples
protons, neutrons, mesons
What are hadrons made off?
Particles that are made of quarks
Hadrons (Baryons):
Particles made of 3 quarks
E.g protons and neutrons
Hadrons (Mesons):
particles made up of a quark and an antiquark.
What’s the building blocks for all matter
Quarks
Leptons
How many know quarks are there, that make up the standard model (name them)
Up
Down
Top
Bottom
Charm
Strange
Each quark is unique and independent (all fundamental).
The main properties, interested in are: charge, baryon number, strangeness, spin.
What’s the charge for all the positive and negative quarks?
Positive +2/3
Negative -1/3
What’s the relationship between the baryon number, the spin, and the strangeness?
Baryon no. the same for all quarks, (+⅓), so is the spin (+½) and the strangeness (0), except for the strange quark (-1).
What’s a proton made out off, and what’s its charge?
Protons made of 2 up, 1 down (uud), the charge of up quark is +⅔e , charge down quark is -⅓e, therefore total charge is +1e.
What are neutrons made of, and what’s their charge?
Neutron made up of 1 up, 2 down (udd), total charge is 0.
Existence of neutrinos discovered when…
trying to explain beta decay, in terms of conservation laws (neutrinos are what make up for the missing energy, during beta decay).
Out of the 3 types of neutrinos which one are we interested in?
interested in electron neutrino and electron antineutrino
What happens in beta decay?
In beta decay, unstable nucleus decays into a proton, an electron, and an electron antineutrino.
What’s emitted from Alpha radiation
Alpha radiation (emission of helium nuclei)
What’s emitted from Beta radiation?
Beta radiation (emission either electrons or positrons)
What is emitted from Gamma radiation?
Gamma radiation (emission of high-energy gamma photons)
What is every type of radiation of result of?
Change that occurs to the neutrons or protons
What are the 2 types of beta decay
Beta Plus Decay
Beta Minus Decay
What is always conserved during beta decay
The nucleon no. A and proton (atomic) no. Z are conserved, as is total charge.
What happens during beta-minus decay?
Neutron decays into a proton, electron and an electron antineutrino
What happens during beta-plus decay?
In beta+ decay, a proton decays into a neutron, a positron and an electron neutrino.
Quark transformation:
Beta-minus decay, neutron to proton
Beta-plus decay, proton to neutron
