FUNDAMENTAL PARTICLES

ABSTRACT

We and all things around us are made of atoms.

Protons, electrons, neutrons, neutrinos and even quarks are often featured in news of scientific discoveries. All of these, and a whole "zoo" of others, are tiny sub-atomic particles too small to be seen even in microscopes. While molecules and atoms are the basic elements of familiar substances that we can see and feel, we have to "look" within atoms in order to learn about the "elementary" subatomic particles and to understand the nature of our Universe and materials that make up the Universe. This paper will try to answer the following questions:

•        What are the Elementary Constituents of Matter?

•        What are the forces that control their behaviour at the most basic level?

•        What kind of equipment is used to detect them?

•        What are the benefit of their study to life in general?

                  INTRODUCTION
Atoms were postulated long ago by the Greek philosopher Democritus, and until the beginning of the 20th century, when modern particle science was formed, atoms were thought to be the fundamental indivisible building blocks of all forms of matter. The discovery of the atomic nucleus in the gold foil experiment of Geiger, Marsden, and Rutherford was the foundation of the field. The components of the nucleus were subsequently discovered in 1919 (the proton) and 1932 (the neutron).

    INTRODUCTION CONT.

•        In the 1920s the field of quantum physics was developed to explain the structure of the atom. The binding of the nucleus could not be understood by the physical laws known at the time. Based on electromagnetism  alone, one would expect the protons to repel each other. In the mid-1930s, Yukawa proposed a new force to hold the nucleus together, which would eventually become known as the strong nuclear force. He speculated that this force was mediated by a new particle called a meson.

WHAT IS A FUNDAMENTAL PARTICLE?

•        An elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic particles of the universe from which all larger particles are made.

•        The science of this study is called Particle Physics, Elementary Particle Physics or sometimes High Energy Physics (HEP).

INSIDE OF AN ATOM

The central nucleus contains protons and neutrons which in turn contain quarks. Electron clouds surround the nucleus of an atom. The science of particle physics surged forward with the invention of particle accelerators that could accelerate protons or electrons to high energies and smash them into nuclei — to the surprise of scientists, a whole host of new particles were produced in these collisions. By the early 1960s, as accelerators reached higher energies, a hundred or more types of particles were found. Could all of these then be the new fundamental particles?

 

A SENSE OF SCALE

There are two basic sets of particles: the quarks and leptons (among the leptons are electrons and neutrinos), and a set of fundamental forces that allow these to interact with each other. By the way, these "forces" themselves can be regarded as being transmitted through the exchange of particles called gauge bosons. An example of these is the photon, the quantum of light and the transmitter of the electromagnetic force we experience every day.

MATTER AND FORCES

QUARKS

•       Most of the matter we see around us is made from protons and neutrons, which are composed of up and down quarks.

•       There are six quarks, but physicists usually talk about them in terms of three pairs: up/down, charm/strange, and top/bottom. (Also, for each of these quarks, there is a corresponding antiquark.)

•       Quarks have the unusual characteristic of having a fractional electric charge, unlike the proton and electron, which have integer charges of +1 and -1 respectively. Quarks also carry another type of charge called color charge, which we will discuss

Is the whole Universe made only of quarks and electrons?

No! There are also neutrinos! n

Electron, proton and neutrons are rarities!

For each of them in the Universe there is 1 billion neutrinos.

Neutrinos are the most abundant matter-particles in the Universe!

All stable matter around us can be described using electrons, neutrinos, u and d “quarks

 

•       It has been found by experiment that the emitted beta particle  has less energy than 0.272 MeV

•       Neutrino accounts for the ‘missing’ energy

 

Fundamental blocks

•       Two types of point like constituent

 

•       Plus force carriers (will come to them later)

•       For every type of matter particle we've found, there also exists a corresponding antimatter particle, or antiparticle.

•       Antiparticles look and behave just like their corresponding matter particles, except they have opposite charges.

 

Generations of quarks and leptons

3 Families (or Generations)

The particles of ordinary matter

Anti-matter

•        For every fundamental particle of matter there is an anti-particle with same mass and properties but opposite charge

Quarks and colour

FUNDAMENTAL FORCES

•       Although there are apparently many types of forces in the Universe, they are all based on four fundamental forces:

•       Gravity, Electromagnetic force, Weak force and Strong force.

 

•       The strong and weak forces only act at very short distances and are responsible for holding nuclei together.

 

•       The electromagnetic force acts between electric charges.

•       The gravitational force acts between masses.

 

•       Pauli's exclusion principle is responsible for the tendency of atoms not to overlap each other, and is thus responsible for the "stiffness" or "rigidness" of matter, but this also depends on the electromagnetic force which binds the constituents of every atom.

 

 

•       All other forces are based on these four. For example, friction is a manifestation of the electromagnetic force acting between the atoms of two surfaces, and the Pauli exclusion principle, which does not allow atoms to pass through each other.

 

•       The forces in springs modeled by Hooke’s law are also the result of electromagnetic forces and the exclusion principle acting together to return the object to its equilibrium position.

 

•       Centrifugal forces are acceleration forces which arise simply from the acceleration of rotating frames of reference

Force Particles (summary)

Forces at the fundamental level

•       The particles (quarks and leptons) interact through different “forces”, which we understand as due to the exchange of “field quanta” known as “gauge bosons”.

The Standard Model

Beyond the Standard Model:Unification of forces

PARTICLE ACCELERATORS

•        Particle accelerators are machines that speeds up particles to increasingly higher energies.

•        It’s a chain of machines each boosting the energy of a beam of particles.

•        In the Large Hadron Collider (LHC) – the last element in this chain – particle beams are accelerated up to the record energy of 4 TeV per beam.

•        The proton source is a simple bottle of hydrogen gas. An electric field is used to strip hydrogen atoms of their electrons to yield protons.

•        These also speed protons, antiprotons, electrons, or   positrons to near the speed of light and then make them collide head-on with each other or with   stationary targets.

 

Fig 10: Matter and Antimatter collision

When particles of matter and antimatter collide they annihilate each other, creating conditions like those that might have existed in the first fractions of a second after the big bang.

•        In an accelerator, focusing magnets and bending magnets guide the beam of particles around a ring. (Only a few of the bending magnets are shown here). High frequency microwave (RF) cavities accelerate the beams as they pass through.

 

30 km

PARTICLE DETECTORS

•       To observe and interpret the results of collisions, particle detectors have to be developed that can track and analyze the particles that fly apart and disappear in nanoseconds.

•       The detectors gather clues about the particles – including their speed, mass and charge – from which physicists can work out a particle's identity.

•       Particles produced in collisions normally travel in straight lines, but in the presence of a magnetic field their paths become curved. Electromagnets around particle detectors generate magnetic fields to exploit this effect. Physicists can calculate the momentum of a particle – a clue to its identity – from the curvature of its path

 

•       Modern particle detectors consist of layers of subdetectors, each designed to look for particular properties, or specific types of particle. Tracking devices reveal the path of a particle; calorimeters stop, absorb and measure a particle’s energy; and particle-identification detectors use a range of techniques to pin down a particle's identity.

BENEFITS/APPLICATIONS

•        Medicine

    Particle accelerators and detectors first developed for particle physics are now used by every major medical center in the nation to treat and diagnose millions of patients.

•       Homeland Security

    From scanning cargo in ports to monitoring nuclear waste, the same advanced detector technology that physicists use to analyze particles also better protects the nation.

•       Industry

    Particle physicists rely on industry to produce and advance the millions of components that experiments require, putting companies on a fast-track towards new products and life-changing technologies.

 

CONCLUSION

    The study of fundamental particles and forces though is seemingly a green area of research in the world of science but no doubt have contributed immensely to science and engineering and also to life generally. There is yet a great anticipation for more discoveries as the Large Hadron collider (LHC) at CERN gets to work. One big goal is to unite all forces with one theory. We have already seen some convergence of the forces, but the question is, beyond the quark model can we get the Grand Unified theory (GUT) and what would that do to the world of science and engineering and to our idea of reality?  Only time will tell.

 

REFERENCES

1.  Sears and Zemansky’s University physics, by Hugh D. young and Roger A. Freedom.

2.  The Particle Odyssey: A Journey to the Heart of the Matter by Michael Marten, Christine Sutton, Frank Close. Oxford Press (2002)

3. The Charm of Strange Quarks : Mysteries and Revolutions of Particle Physics by R. Michael Barnett, Henry Muehry, Helen R. Quinn. American Institute of Physics, (2000)

4. The Particle Adventure (Lawrence Berkeley Lab) http://www.particleadventure.org/particleadventure/

5. Inquiring Minds (Fermi National Lab.) http://www.fnal.gov/pub/inquiring/index.html

6. The World of Beams (Center for Beam Physics, Lawrence Berkeley Lab), http://cbp-1.lbl.gov/

7. Big Bang Science, (Particle physics & Astronomy ResearchCouncil, UK) http://hepwww.rl.ac.uk/pub/bigbang/part1.html

8. Introduction to elementary Particle Physics by Emmanuel Olaiya March 2005

 

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