Edexcel A2 Physics Unit 4 : Chapter 3 : Particle Physics3.3: Detectors & Particle Interaction
Prepared By: Shakil Raiman
3.13.1: Principle of Detection In experimental and applied particle physics, nuclear physics, and
nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify high-energy particles, such as those produced by nuclear decay, cosmic radiation, or reactions in a particle accelerator. Modern detectors are also used as calorimeters to measure the energy of the detected radiation. They may also be used to measure other attributes such as momentum, spin, charge etc. of the particles.
Geiger-Muller tube, Bubble chamber, cloud chamber these are examples of detector which use the principle of ionization.
3.13.2: GM tube & Ionisation
3.13.2: GM tube & Ionisation
3.13.3: Bubble Chamber: A bubble chamber is a vessel filled with a superheated
transparent liquid (most often liquid hydrogen) used to detect electrically charged particles moving through it.
The bubble chamber is similar to a cloud chamber in application and basic principle. It is normally made by filling a large cylinder with a liquid heated to just below its boiling point. As particles enter the chamber, a piston suddenly decreases its pressure, and the liquid enters into a superheated, metastable phase. Charged particles create an ionisation track, around which the liquid vaporises, forming microscopic bubbles. Bubble density around a track is proportional to a particle's energy loss.
3.13.3: Bubble Chamber: Bubbles grow in size as the chamber expands, until they are large
enough to be seen or photographed. Several cameras are mounted around it, allowing a three-dimensional image of an event to be captured. Bubble chambers with resolutions down to a few μm have been operated.
The entire chamber is subject to a constant magnetic field, which causes charged particles to travel in helical paths whose radius is determined by their charge-to-mass ratios and their velocities. Since the magnitude of the charge of all known charged, long-lived subatomic particles is the same as that of an electron, their radius of curvature must be proportional to their momentum. Thus, by measuring their radius of curvature, their momentum can be determined.
3.13.3: Bubble Chamber:
3.13.3: Bubble Chamber:
3.13.4: The Large Hadron Collider:The Large Hadron Collider (LHC) is the highest-energy particle collider ever made and is considered as "one of the great engineering milestones of mankind."[1] It was built by the European Organization for Nuclear Research (CERN) from 1998 to 2008, with the aim of allowing physicists to test the predictions of different theories of particle physics and high-energy physics, and particularly prove or disprove the existence of the theorized Higgs particle[2] and of the large family of new particles predicted by supersymmetric theories.[3] The LHC is expected to address some of the still unsolved questions of physics, advancing human understanding of physical laws. It contains seven detectors each designed for specific kinds of
exploration.
3.13.4:Compact Muon Solenoid
3.13.4: LHC Dectectors: CMS – the Compact Muon Solenoid LHCb – Large Hadron Collider beauty experiment ALICE – A Large Ion Collider Experiment ATLAS – A Toroidal Lhc ApparatuS
3.13.4: Detectors Capability: Measure the directions, momenta, and signs of charged particles. Measure the energy carried by electrons and photons in each direction
from the collision. Measure the energy carried by hadrons (protons, pions, neutrons, etc.)
in each direction. Identify which charged particles from the collision, if any, are electrons. Identify which charged particles from the collision, if any, are muons. Identify whether some of the charged particles originate at points a few
millimetres from the collision point rather than at the collision point itself (signalling a particle’s decay a few millimetres from the collision point).
3.13.4: Detectors Capability: Infer (through momentum conservation) the presence of undetectable
neutral particles such as neutrinos. Have the capability of processing the above information fast enough to
permit flagging about 10-100 potentially interesting events per second out of the billions collisions per second that occur and recording the measured information.
The detector must also be capable of long and reliable operation in a very hostile radiation environment.
3.14.1: Particle Interaction: Creation:
Matter can appear out of nowhere, as if by magic, from energy. It is converted from energy according to E=mc2
Annihilation: Just as matter can appear spontaneously through a conversion from energy,
so energy can appear through the disappearance of mass. This is the source of energy in nuclear fission and fusion. In both reactions, the sum of the masses of all matter involved before the reaction is greater than the sum of all the mass afterwards. This mass difference is converted into energy as heat.
If a particle and its antiparticle meet, they will spontaneously vanish from existence to be replaced by the equivalent energy: we call this interaction annihilation.
3.14.1: Particle Interaction:
3.15.1: Standard Model: Standard Model of Particle Physics:
The current theory, which identifies 12 fundamental particles from which all matter is made
Quark: The fundamental particles from which protons, neutrons (and some
other particles) are made. There are 6 types of quark.
Leptons: Fundamental particles with a very small mass. The electron is one of
the six types of lepton.
3.15.2: Quarks:
3.15.3: Leptons:
3.15.3: Particle Reactions: Hadron:
Groups of quarks held together by strong forces (baryons and mesons).
Baryon: Hadron made from three quarks bound together. The protons and neutron are both baryons
Meson: Hadron made from two quarks bound together. The pion and the kaon are the most common examples of mesons. Pions: Pions are the lightest of the meson family of fundamental
particles and are often produced in particle physics experiment.
3.15.3: Baryons and Mesons:
3.15.3: Baryon number and lepton number:
Baryon Number: The baryon number is one third of the difference between the number of quarks and the number of antiquarks within a system.
Lepton Number: The number of leptons, minus the number of antileptons, within a system.
For a reaction to be possible, the lepton number and baryon number must be conserved.
3.15.4: Reactions conserve properties:
The combination of mass/energy must be equal before and after the reaction.
Momentum must conserve. Charge must conserve. the lepton number and baryon number must be
conserved.
3.15.4: Alpha and beta-minus decay: Alpha decay: Radioactive decay in which the nucleus releases an alpha
particle (a helium nucleus). In alpha decay the mass number decreases by 4 and the proton number by 2.
Radioactive decay in which an electron and an antineutrino are emitted as a neutron in the nucleus turns into a proton. The atomic number of the parent atom is increased by 1
3.15.6: Leptons and Antileptons:
3.15.6: Particle and properties:
3.15.6: Reactions:
3.15.6: Reactions:
3.15.6: Exchange Bosons: There are four other particles that are not matter particle. These are
known as exchange bosons. They interact by the four forces of nature. Electromagnetic force: The force experienced by a current-carrying
conductor in a magnetic field. Strong Nuclear force: The force which binds nucleons together in the
nucleus. Weak Nuclear force: One of the four fundamental forces. The weak
nuclear force is responsible for beta decay. Gravity: cause due to mass of objects.
3.15.6: Exchange Bosons Particles:
3.15.6: Exchange Bosons Particles:
Thank You All
Wish you all very good luck.
