FINDING THE KEY TO THE COSMOS
WITH THE LARGE HADRON COLLIDER
6/8/11
Nienke Adamse
Introduction
As a scientist, I am on a mission to find the building blocks of nature, the subatomic
particles. I am trying to solve the mystery of how the universe came into existence
by delving deep into atoms. The atom is actually the key to the cosmos. To get a
glimpse of these particles we are using giant machines. These machines are called
colliders (or atom smashers) and they accelerate particles to almost the speed of
light. When these high-speed particles collide we imitate the Big Bang on a
microscopic scale.
The Big Bang Theory states that our universe was created about 13 billion years
ago. A huge amount of energy was converted into matter within tenths of a second.
The matter kept interacting and changing as it spread outward and eventually
became the matter that our universe is made up of: from stars, to planets to human
beings.
Matter is made up of atoms that consist of smaller elementary particles. To
investigate elementary particles, I, as a physicist, need to recreate the conditions
that occurred less than a second after the Big Bang. I hope to gain fundamental
insights into the make up of a proton and what holds a nucleus together. I am also
looking for new types of forces and particles, for example, the Higgs particle. As yet,
this particle is a hypothetical particle invoked to explain why the carriers of the
electroweak force (the W and Z bosons) have mass. “Peter Higgs and two Belgian
researchers (who worked independently of Higgs) came across the same idea for
settling the puzzle in 1964. If there is an otherwise undetectable field filling the
universe (now called the Higgs field), it could have been associated with a
previously unknown kind of boson, the Higgs particle, which has mass. “ (Answer,
2006) To sum up, Higgs Particles are believed to be responsible for mass of objects
in the universe.
I am also in search of the so-called ‘dark matter’: the invisible ‘stuff’ that seems to
hang around galaxies. I hope that with the experiments in the collider we will be
making dark matter.
Another mystery that I am very curious about is a GUT (Grand Unified Theory); I
hope we can find one. Grand Unified Theory combines three forces: strong and weak
nuclear and electromagnetic force into one unified force. Also, for centuries
scientists have tried to find a field theory that unifies electromagnetic force with
gravity. So far, however, they have not had any success. If we want to unify the four
forces of nature, we must find a way of combining general relativity with quantum
mechanics. However, these two theories have hardly anything in common. My quest
and that of other physicists would be to find the ultimate theory, a theory of
quantum gravity. And last but not least, I want to know if we will be able to find the
so-called graviton; a bosom particle that carries the force of the gravity force field
(See picture 1).
Particle accelerators
Although most people think the giant particle accelerators, such as the SLAC in
Stanford, the longest linac (linear accelerator) in the world or the Large Hadron
Collider (LHC) in Geneva, the largest cyclotron (circular accelerator) in the world,
are the only colliders, but most of us have particle accelerators in our homes. The
CRT (Cathode Ray Tube) in any TV or computer monitor is a low energy particle
accelerator. The CRT takes particles (electrons) from the cathode, speeds them up
and changes their direction by electromagnets and smashes them into phosphorous
molecules on the screen. This collision results in a lighted spot, or pixel, on the TV or
monitor (See picture 2).
The Large Hadron Collider
The Large Hadron Collider (LHC) is the world's largest and highest-energy particle
accelerator. It was built by the European Organization for Nuclear Research (CERN)
with the intention of testing various predictions of high-energy physics. It was built
in collaboration with over 10,000 scientists and engineers from over 100 countries,
as well as hundreds of universities and laboratories. The collider uses mostly
protons as colliding particles. The LHC lies in a tunnel 27 kilometers in
circumference and as much as 175 meters beneath the Franco-Swiss border near
Geneva, Switzerland (See picture 3).
The collider is a synchrotron collider, which is a cyclotron collider where the
particles reach a speed of almost light speed and where the energy of the particles is
being intensified in increasing particle mass.
Hydrogen atoms are entering the source chamber of the linear accelerator of the
LHC where the electrons are stripped off. Leaving only the hydrogen nuclei; protons
with a positive charge. This positive charge makes it possible to be accelerated by
an electric field. This initial acceleration brings them up to a speed of a third of light
speed. The protons then enter the booster where they are divided up into four
beams in order to maximize the intensity of the beam. Each beam occupies one ring
of the booster. The movement of the protons in circles accelerates them more than
in a linear track. The circles of the booster are 175 meters in circumference. While
the packages of protons are circulating in the booster, a pulsating electric field
accelerates them even more. Electromagnets exert force on the particles at right
angles of their motion and bend the beams around the circle. The electromagnets
are very powerful because they are made with superconducting materials. The
booster accelerates the particles up to 91.6% of the speed of light and squeezes
them closer together. Recombining the packets into a single beam, the protons are
being flung into the Proton Synchrotron. The Proton Synchrotron is 628 meters in
circumference and the protons circulate for 1.2 seconds with a speed of 99.9% of
the speed of light. At this point they cannot accelerate any more and the point of
transition is reached. The energy added to the protons by the pulsating electric field
cannot increase the speed, because the protons have almost reached the maximum
speed of light, thus the protons would become heavier. The energy of each proton
has risen to 25 GEV. The protons are now 25 times heavier than they are at rest. The
protons are now channeled into the Super proton Synchrotron, a huge ring with a
circumference of 7000 meters. Here, the energy of the protons is increased to 450
GEV. They now become energized enough to be launched into the Large Hadron
Collider, or LHC, a gigantic ring with a circumference of 27km, which lays 175 meter
under the ground. There are two vacuum pipes within this ring containing proton
beams traveling in opposite directions. The counter rotating beams cross over in the
four detector caverns where they can be made to collide. The detectors are made up
of huge electromagnets and each magnet weighs almost 2,000 tons. It sits inside a
large, red octagon-shaped cavern, and is surrounded by layers of scientific
equipment. The detector is called CMS for Compact Muon Solenoid.
The energy of the collision is double that of the individual opposing protons. The
debris of this collision is tracked into the large detectors. The speed of the protons is
now very near the speed of light and they circulate the ring 11000 times each
second! At the point of collision each proton carries energy of 7TEV and they are
7000 times heavier than at rest. In order to reach such a high electric field, the
magnets of the electromagnets are kept at a temperature of 3 Kelvin. Here, the
magnets become superconductors, i.e., the electromagnetic force flows without any
resistance. Steering magnets bring the protons into a collision course; the protons
collide with a total energy of 14 TEV, which simulates a similar state of moments
after the Big Bang. Computers connected to the detectors analyze the data of the
particles that are formed out of this collision, some of them with a life span of a
millionth of a second. These particles will give us more information about what
happened during the Big Bang, but it will give us also valuable information about
what happens in the subatomic world (See picture 4).
The Higgs particle
Finding the Higgs particle, sometimes called the ‘God particle,’ was the primary
reason for building the super collider. Only a super collider could have the energy
necessary to produce and detect the Higgs boson. What is this particle and why is
finding it so important to us physicists? The theory that physiscis have developed to
explain the world and what holds it together is called the Standard Model Theory. It
is a simple and comprehensive theory that explains all the hundreds of particles and
their interactions with each other: six quarks, six leptons and the particles that carry
the four known forces, the force carrier particles. All the known matter particles are
composites of quarks and leptons, and they interact by exchanging force carrier
particles. The Standard Model, however, cannot explain why a particle has a certain
mass. That is why physicists have theorized the existence of the so-called Higgs
Field. This field interacts, in theory, with particles to give them mass (if they have
mass). The Higgs Field requires a particle: the Higgs boson. This particle has never
been observed, but we are looking for it with great enthusiasm because finding it
would mean we would have found part of the puzzle of why most of the known
particles become massive and why there is a difference between the
electromagnetic force field carrying particle, the photon, which is mass-less and the
W and Z bosons, which mediate the weak force and do have mass. Finding the Higgs
bosom would be finding the integral and pervasive component of the material
world.
Atlas
To create a real Higgs particle (particles that are given enough energy to exist as real
particles and not as extremely short time virtual particles), we need to fire particles and
anti particles together to create a fireball of energy. Out of this fireball we look for decay
products that indicate that we have found or created a Higgs boson. The energy needed to
find the Higgs boson depends on the Higgs mass. Since we do not know for sure what the
mass of a Higgs boson is, we expect it to be between 114 and 200 GEV/c. 2 We just need
to collect a lot of data of the Higgs signals from all the collisions we create.
The detector of the GHC that should be able to detect the Higgs particle is called Atlas. It

is a gigantic, seven story high apparatus designed to enable scientists to detect the decay
particles of a high-energy collision. It is a multi-component detector that tests different
aspects of a collision event. Each component of the detector is used to measure the
energies of different particle types. The detector is spherical or cylindrical in shape
because during a colliding beam experiment, the particles radiate in all directions. The
inner section, or Tracking Chamber, measures the tracks of charged particles, which are
bent by thin foils of superconducting magnets. Outside of these are two calorimeter
devices, the Electric Calorimeter and the Hadron Calorimeter, which measure the
energies of the particles. Finally the Muon Spectrometer in the Muon Chamber measures
the tracks of muons, which are bent in the field of the superconducting Toroidal magnets.
An electron, for example, will travel through the inner detector, leaving a track behind
before it stops in the Electromagnetic Calorimeter. A photon behaves in a similar way,
but it leaves no track in the tracking chamber. A proton leaves a track and interacts
primarily in the Hadronic Calorimeter. A neutron behaves in a similar way but it also
leaves no track before it arrives in the Hadronic Calorimeter. A muon, on the other hand,
passes all the way through Atlas leaving tracks behind. Finally a neutrino passes through
Atlas without being detected at all. (See picture 5)
Picture 5
References
Al-Khalili, J. (2003) Quantum. A Guide for the Perplexed
London, UK: Weidenfeld and Nicolson
Atlas. Retrieved from
http://www.bing.com/videos/watch/video/atlas-episode-2-the-particlesstrike-back-part-1
Krane, K. (1996) Modern Physics.
USA: Wiley
Large Hadron Collider. Received from
http://www.youtube.com/watch?v=XnX2_r0o4OA&feature=player_embed
Lederman, L. (2006). The God Particle. If the Universe Is the Answer, What Is the
Question?
New York, NY: Mariner Books
What are Higgs particles? Received from
http://answers.yahoo.com/question/index?qid=1006050112158