Edexcel A2 Physics
Unit 4 : Chapter 3 : Particle Physics
3.3: Detectors & Particle Interaction
Prepared By: Shakil Raiman
3.13.1: Principle of Detection
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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:
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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:
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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 highestenergy 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:
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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:
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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:
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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:
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Matter can appear out of nowhere, as if by magic, from energy. It is
converted from energy according to E=mc2
 Annihilation:
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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:
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The current theory, which identifies 12 fundamental particles from
which all matter is made
 Quark:
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The fundamental particles from which protons, neutrons (and some
other particles) are made. There are 6 types of quark.
 Leptons:
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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:
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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:
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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.