The laws of physics have to do with the forces and correlations between the tangible objects of our surroundings, which in physics are described as matter, and the energy emissions between these objects, that are in general described as radiation. In order to do that, we must reduce the study to the smallest possible constituents of both, which in physics are called particles. The term, even though it applies to, does not define real physical entities.
At this time, particles are understood and defined as excitations of quantum fields that interact according to their dynamics. The definitions of the fundamental fields of particle physics are incorporated to what scientists call Standard Model. To put it as simplistically as possible, Particle Physics is the study of the Standard Model’s content of particles along with possible extensions like the recent discovery of Higgs boson.
Many would think that particle physics belongs to the theoretical models that have no practical application. That is completely incorrect. Without their study, the Internet and touchscreens would be impossible. Particle physics is also responsible for superconductors, cyclotrons and PET imaging. Actually half the current medical technology is based on particle physics. Other practical applications can be found in computing, national security and workforce development. These fields alone are demonstrative of the importance of this branch of research.
To understand what this is all about, let’s start with the basics of particle physics. It all starts with the theory. To comprehend what we want to research, we formulate a theoretical model upon which to make the necessary comparisons and tests. This model includes the framework, the mathematics and the experimentation required. It also makes provisions and predictions about the future. As aforementioned, at this time, the model created and used is the Standard Model which offers the basis for further exploration by extrapolating parameters and using results of experiments that are more or less predictable as to their outcomes.
The point of the exercise is to reach a better understanding of nature’s building blocks. This is a complicated effort due to the challenges of quantum chromodynamics. To work on the issues involved, scientists use three major theories. The quantum field, the effective field and the lattice field theories. These will be explored in later articles, but for now we will begin with what these theories actually work with. The particles. It will be useful before we reach more advanced issues like the Higgs Mechanism, supersymmetry, the Randall-Sundrum models and the Preon theory.
All these are the fundamental principles upon which string theory was developed and it currently represents the best effort of the famous “theory of everything” or theory of unification of quantum mechanics and the general theory of relativity. It has been the point of convergence for scientists for years. The effort to explain everything through one single theory.
The first question to answer is what exactly the Standard Model is. It explains the state and classifications of all the elementary particles. There are three kinds of interaction between these particles: strong, weak and electromagnetic. The standard model describes these interactions through gauging with mediating particles. Currently, 24 fundamental particles are included in this model. Actually, since the existence of matter and anti-matter has been confirmed, it’s 12 particles and their anti-particles. These are separated in three categories:
1. The Bosons
These are the mediating particles that are used to gauge the interactions between the elementary particles. These are separated in three species:
a. The gluons
The quarks interact with each other through strong relations. These relations are mediated through 4 pairs of gluons.
b. The W–,W+ and Z bosons
Wherever there is a weak interaction between two particles of different kinds, this is mediated by these three species. The plus and minus signs indicate a +1 or -1 electrical charge, while Z bosons are neutrally charged.
c. The photons
Between two electrically charged particles there is electromagnetic force. Photons mediate that force.
2. The Fermions
These are particles that respect the Pauli Exclusion Principle and they are classified depending on what charges they carry. There are 12 pairs (particles and corresponding anti-particles).
Six of these pairs are called quarks and they are separated to flavors:
They combine to form more composite particles that are called hadrons. Examples of these hadrons are the protons and the neutrons. A phenomenon called color confinement makes it impossible to isolate the quarks, so they are observed only within baryons and mesons.
The other six are called leptons. They do not undergo strong interactions and they are divided into two sections: the electron-like and the neutrinos. The three electron like are:
- The electron which governs almost everything that has to do with chemistry
- The muon
- The Tau
The electron neutrino, the muon neutrino and the tau neutrino are the remaining three leptons and the reason they are called neutrinos is that they actually do not interact with anything.
3. Higgs Boson
This is the key building block in the standard model. It is a massive scalar particle, and it explains why the other elementary particles, except the photons and the gluons, are massive. It was a theoretical concept until on Jul 04, 2012 when a particle with similar properties was isolated in the Large Hadron Collider.
In future articles we will explain the spins, color charges and the other properties of these elementary particles and how the study of these properties is used to explain not only what is defined as matter, but also how they react to higher concepts like high-energy collisions and cosmic rays. We will also be discussing the four fundamental forces or interaction: the strong, the weak, the electromagnetic and the gravitational. And then we will try to explain string theory as simplistically as possible.