All the Particles in the Universe- The Standard Model

In the previous post we had an overview of Quantum Mechanics, what is it, and several theories regarding the field.

Quantum Mechanics is that field of study which involves the smallest or the most fundamental particles of the universe and their properties which differs from Classical Physics theories.

The Universe is Made of Particles and all these particles have their own properties and ways of interaction. All the 'known' particles till today have been mapped together in the 'Standard Model' of Physics.

The Standard Model is missing a few puzzle pieces (conspicuously absent are the putative particles that make up dark matter, those that convey the force of gravity, and an explanation for the mass of neutrinos), but it provides an extremely accurate picture of almost all other observed phenomena.

Yet for a framework that encapsulates our best understanding of nature’s fundamental order, the Standard Model still lacks a coherent visualization. Most attempts are too simple, or they ignore important interconnections or are jumbled and overwhelming.

Consider the most common visualization, which shows a periodic table of particles:

A new Interpretation, 2013:

 

QUARKS:

Matter particles come in two main varieties, leptons and quarks. (Note that, for every kind of matter particle in nature, there is also an antimatter particle, which has the same mass but is opposite in every other way. As other Standard Model visualizations have done, we elide antimatter, which would form a separate, inverted double simplex.)

Let’s start with quarks and in particular the two types of quarks that make up the protons and neutrons inside atomic nuclei. These are the up quark, which possesses two-thirds of a unit of electric charge, and the down quark, with an electric charge of −1/3.

Up and down quarks can be either “left-handed” or “right-handed” depending on whether they are spinning clockwise or counterclockwise with respect to their direction of motion.

LEPTONS:

Now let’s turn to the leptons, the other kind of matter particles. Leptons come in two types: electrons, which have an electric charge of −1, and neutrinos, which are electrically neutral. Now let’s turn to the leptons, the other kind of matter particles. Leptons come in two types: electrons, which have an electric charge of −1, and neutrinos, which are electrically neutral.

Now let’s turn to the leptons, the other kind of matter particles. Leptons come in two types: electrons, which have an electric charge of −1, and neutrinos, which are electrically neutral.

Forces and carrier particles

There are four fundamental forces at work in the universe: the strong force, the weak force, the electromagnetic force, and the gravitational force. They work over different ranges and have different strengths. Gravity is the weakest but it has an infinite range. The electromagnetic force also has infinite range but it is many times stronger than gravity. The weak and strong forces are effective only over a very short range and dominate only at the level of subatomic particles. Despite its name, the weak force is much stronger than gravity but it is indeed the weakest of the other three. The strong force, as the name suggests, is the strongest of all four fundamental interactions.

Three of the fundamental forces result from the exchange of force-carrier particles, which belong to a broader group called “bosons”. Particles of matter transfer discrete amounts of energy by exchanging bosons with each other. Each fundamental force has its own corresponding boson – the strong force is carried by the “gluon”, the electromagnetic force is carried by the “photon”, and the “W and Z bosons” are responsible for the weak force. Although not yet found, the “graviton” should be the corresponding force-carrying particle of gravity. The Standard Model includes the electromagnetic, strong and weak forces and all their carrier particles, and explains well how these forces act on all of the matter particles. However, the most familiar force in our everyday lives, gravity, is not part of the Standard Model, as fitting gravity comfortably into this framework has proved to be a difficult challenge. The quantum theory used to describe the micro world, and the general theory of relativity used to describe the macro world, are difficult to fit into a single framework. No one has managed to make the two mathematically compatible in the context of the Standard Model. But luckily for particle physics, when it comes to the minuscule scale of particles, the effect of gravity is so weak as to be negligible. Only when matter is in bulk, at the scale of the human body or of the planets for example, does the effect of gravity dominate. So the Standard Model still works well despite its reluctant exclusion of one of the fundamental forces.

So far so good, but...

...it is not time for physicists to call it a day just yet. Even though the Standard Model is currently the best description there is of the subatomic world, it does not explain the complete picture. The theory incorporates only three out of the four fundamental forces, omitting gravity. There are also important questions that it does not answer, such as “What is dark matter?”, or “What happened to the antimatter after the big bang?”, “Why are there three generations of quarks and leptons with such a different mass scale?” and more. Last but not least is a particle called the Higgs boson, an essential component of the Standard Model.

On 4 July 2012, the ATLAS and CMS experiments at CERN's Large Hadron Collider (LHC) announced they had each observed a new particle in the mass region around 126 GeV. This particle is consistent with the Higgs boson but it will take further work to determine whether or not it is the Higgs boson predicted by the Standard Model. The Higgs boson, as proposed within the Standard Model, is the simplest manifestation of the Brout-Englert-Higgs mechanism. Other types of Higgs bosons are predicted by other theories that go beyond the Standard Model.

On 8 October 2013 the Nobel prize in physics was awarded jointly to François Englert and Peter Higgs “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider”.

So although the Standard Model accurately describes the phenomena within its domain, it is still incomplete. Perhaps it is only a part of a bigger picture that includes new physics hidden deep in the subatomic world or in the dark recesses of the universe. New information from experiments at the LHC will help us to find more of these missing pieces.

Feel free to ask your question(s) in the comment, and I'll be happy to respond. All the best!

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Written By:

Shubham Sagar,

Code Star

E-mail: sk0374391@gmail.com