PARTICLE DECAY (AT THE SUBATOMIC LEVEL) AND THE FUNDAMENTAL FORCES

WHAT ARE THE FUNDAMENTAL FORCES?

There are 4 fundamental forces in the universe :-

1. Strong Nuclear Force (Due to quarks binding together to form hadrons, which include protons and neutrons. Carried by the gluon)
2. Weak Nuclear Force (Facilitates a change in the atom in some way; thereby causing nuclear reactions)
3. Gravity
4. Electromagnetic force

Nuclear reactions are responsible for changes in the nucleus of an atom while chemical reactions involve the valence shell electrons (electrons in the outermost shell of an atom)..

Nuclear reactions are those in which something in the nucleus “decays”, giving off radiation and changing one element to another.

HOW WAS RADIOACTIVITY DISCOVERED?

Henri becquerel, in 1896, discovered that Uranium emitted radiation that was able to interact with a photographic film

Marie Curie then found out that the element thorium was emitting similar radiation.

Marie Curie, working together with Pierre Curie, took some samples of uranium (it’s ore was known as pitchblende; of the formula UO₂) and purified them. She then noticed that this uranium was unaffected by changes in temperature and observed that energy was constantly emitted from the sample. She named this energy “Radiation”.

She observed that the strength of the Radiation did not vary from element to element, rather every radioactive element emitted the same amount of radiation in a given quantity of the element.
Now, this should imply that this radiation is something common to every element, that is, something fundamental. Marie went on to discover 2 new elements, radium and polonium.

Furthermore, it was observed that the unstable nucleus of the atom emitted 3 types of radiation- alpha, beta and gamma radiation on the basis of their penetrating power (alpha radiation has the least penetrating power while gamma has the highest). Nucleus of an atom becomes unstable when the number of neutrons are much more than the number of protons.

The quantum theory says that we cannot predict the timing of particle emission by a nucleus.
This property of radioactivity is only shown by atoms whose atomic number is greater than 83, since smaller atoms’ protons and neutrons are held together by a much stronger force in the form of the nuclear force.

Therefore, radiation can be described as an unstable nucleus emitting high energy particles to maintain it’s proton to neutron ratio, so as to hold the nucleus together.

Now, since mass can be converted into energy and vice-versa, we can also harness these energies for ourselves.

TYPES OF RADIOACTIVE DECAYS

1. Alpha decay- When the electromagnetic force causes 2 protons and 2 neutrons to be emitted out of the radioactive nucleus. Mass number decreases by 4 and Atomic number decreases by 2 in this case. There are too many protons in this case (N/Z ratio is too low, where N are the number of neutrons and Z is the atomic number, or the number of protons.). For example, alpha decay occurs when Uranium decays to Thorium. An alpha particle is released in this case (equivalent to Helium-4’s nucleus)
2. Beta minus decay- In this case, there are too many neutrons in the nucleus. Therefore, the neutron changes in to a proton and an electron. The electron is released and the proton is retained to maintain the N/Z ratio. The lost electron has a very high energy and is therefore known as a beta particle. (example) Carbon decays to Nitrogen by this method.
3. Beta plus decay– This is opposite to Beta Minus Decay and there are too many protons in the atom. A proton gets converted into a neutron with the release of a positively charged electron (high energy particle; unstable; negligible mass; charge=+1 unit), known as a positive beta particle, or a positron. The mass number (neutrons+protons) stays the same but the atomic number changes.
   
   In all cases, energy is released in the form of ionizing radiation (which can be either gamma rays, alpha particles or beta particles), which has enough energy to knock off an electron from an atom. (and gamma rays have high penetrating capacity too).
   This energy is also able to break through a chemical bond, which is known as the Szilard-Chalmers effect.

RADIOACTIVITY AND PARTICLE PHYSICS (THE STANDARD MODEL)

With the discovery of radioactivity and general relativity describing gravity (however, not completely, which we will discus later), only three fundamental forces (The Strong Nuclear Force, the weak nuclear force and the electromagnetic force) remained to be explained through a unified theory.
The Standard model describes these three forces with high accuracy.

The Standard model says that every particle, is either a fermion (a matter particle), a boson (a force particle) . Fermions obey the Pauli Exclusion Principle, which says that two particles can’t be at the same place at the same time, while bosons can be stacked on top of each other because they don’t follow Pauli’s Exclusion principle.

1. Fermions- We can say that everything that we see around us can be reduced to three species of particles, called the electrons, the up quarks and the down quarks. Protons have 2 up quarks and one down quark, while neutrons have one up quark and 2 down
2. Neutrinos- They’re extremely light and move with speeds close to the speed of light. They’re products of nuclear processes and on Earth, they come from the Sun, or nuclear processes inside the Earth or by cosmic rays hitting Earth’s atmosphere. They have been detected at the Large Hadron Collider in Switzerland. They can be made by particle accelerators too. We know that they come from particles that have been accelerated at speeds which are more than a billion times greater than what humanity can do. They therefore, contain information about their sources, which supposedly are giant “gravitational wells” we have no idea of (most probably black holes in our knowledge, but who knows? They’re may be something else?). We’re trying to detect them by somehow making them collide with matter, which is, transparent (at IceCube in Antarctica). This is made possible by detecting blue light produced by a neutrino’s nuclear reactions with the nucleus of the ice particles. This produces a stream of charged subatomic particles which travel faster in ice than light does in ice. This further causes for blue light to emerge from the atoms, which is detected. Further, we are able to detect their origin, thereby answering the question to where such high-energy particles came from. However, now, even after several years of data collection, we don’t know the source of the neutrinos, and have no idea about how can they help us.
   Therefore, we’re looking for alternatives in the form of the string theory.

If we are able to peer into a black hole (which is the only place where gravity works with the particles of the Standard model), then the Standard Model of the Universe would be complete, and humans, would be able to advance to such a scientific advancement that we will be able to predict and know everything happening, in the universe (or even the multiverse), at all times.

+notice how the image in the background of the post title concerns strings (a nod to the string theory!)