Saturday, October 12, 2013

Crash Course on Particle zoo…

In school we were taught about the proton, neutron and electron – which allegedly made up the basic structure of an atom. We were taught that these are the basic structure of all matter. Well, now that we are grown and no more in school, its time we learn some adult stuff. So here is the crash course, to start with.
Lets recap- We know that an atom has a nucleus, which contains protons and neutrons. Electrons go around them. We also know electrons are negatively charged and have negligible mass. Protons are positive and neutrons are neutral and have equal mass.
Our old friends’ electrons are not alone, they have 5 more brothers and physicists call them flavours. Electron, Muon and tau are negatively charged brothers and electron neutrino , muon neutrino and tau neutrino have no charge. Electrons are smaller than muons which are smaller than tauons. All six together are called ‘Leptons.’
Our other old friends, Proton and Neutrons are actually made of smaller particles. These smaller particles are called Quarks. Quarks come in six flavours. Up (u), down (d), charm (c), strange (s), top (t) and bottom (b).
Protons are made of 2 up quarks and one down quark. Neutrons are made of one up and 2 down quarks. Similarly various other particles are made up of a combination of these quarks. When a particle is made up of 2 quarks it is called a ‘Meson’. When it is made of 3 quarks it is a ‘Baryon’. Protons and neutrons are examples of baryons.
In terms of mass u & d are lighter than c & s, which are lighter than t & b.
Just one thing to remember, these 6 quarks, mentioned above also have an anti-quark each.
So the above are the 12 elementary particles that make up our universe, including you and me. Now for the four fundamental forces of nature, without which the zoo is not complete.
1. The strong force: The strongest force in nature, but has a very small range (just within the nucleus). This force holds the quark together and forms the protons and neutrons.
2. Electromagnetic force: Responsible for electromagnetic emission and absorption.
3. The weak force: It has a smaller range than the strong force. It is an important part of nuclear reactions
4. Gravitational force: He needs no introduction. This though is the weakest of all forces, but has an infinite range.
Now these forces are carried by the so called ‘force particles’ Gluons carry the strong force, photons carry the electromagnetic force and W and Z bosons carry the weak force. Though not a part of the standard model, Gravitons are suggested to carry Gravitational force.
Gluons and photons are massless, while rest of the elementary particles have mass. The reason for this was explained by the Higgs- boson particle. The so called ‘God Particle’ that is making news now and then. Scientists at CERN are trying to hunt it down to conclusively prove its existence. Thank you and hope you had a lovely time.

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