What We Can’t See: The Subatomic World

Human curiosity has seemingly always asked the classic question “What is everything made of?”. The world we live in seems incredibly, infinitely complicated with millions of particles - but what is the key? Scientists answer this question with “the Higgs boson”, something that the press likes to call “The God Particle”, even though the scientists may not agree with that terminology.

"Protons collide at 14 TeV in this simulation from CMS, producing four muons. Lines denote other particles, and energy deposited is shown in blue" (Image: CMS)

The Higgs boson is an elementary particle in the standard model of particle physics. It was formally discovered on 4 July 2012 in the CERN laboratory, Geneva, Switzerland. The term Higgs boson seems to have captured the attention throughout the world. The journal, Science, called it the “breakthrough of the year”. It has been trending so much that there are even bands and beers with same name.

So what is the Higgs boson? Before answering this, I need to talk about matter. When Mendeleev first designed the periodic table, it had only 80 elements - these atoms were considered to be indivisible. A series of developments proved this not to be the case:

  • J.J. Thompson discovered the existence of negatively-charged particles called electrons.

  • Ernest Rutherford found out from his famous “gold foil experiment” that there was something in the centre of an atom where the positive charge is concentrated and named this the nucleus.

  • Neils Bohr published his model which assumes electrons move around the nucleus in a discrete set of orbits.

  • Louis de Broglie proposed that all particles behave to an extent like waves.

The latter was the profound idea which led to development of a mathematical model of atom, describing the electrons as 3D waveforms rather than point particles. This made it mathematically impossible to obtain precise values of both the position and momentum of a particle at a given point in time, known as the Heisenberg’s Uncertainty Principle - the foundation of Quantum Mechanics.

James Chadwick’s long-awaited discovery of the neutron, a particle with no charge but same mass as the proton, “completed” the model: an atom is made up of a nucleus of protons and neutrons, while electrons revolve around it, attracted to the protons in the nucleus by electromagnetic forces.

To enter Quantum Mechanics is to kiss your logical understanding of reality goodbye. In spite of this, it has influenced so many practical applications in real life such as transistors, lasers, and x-rays.

The Standard Model is a collection of theories which are based on atomic symmetry, describing the experimentally observed sub-atomic particles and the forces that dictate their interactions. There are fundamentally 16 elementary particles that define the existence of matter and the energy in the universe. Out of these: 6 are quarks, 6 Leptons and 4 bosons. These particles are too small to be observed by an instrument of observation available at the moment.

Composites of quarks are called hadrons, for example protons and neutrons.

Bosons dictate forces: the electromagnetic forces, the strong and weak nuclear forces and, lastly, gravity. However, gravity is not explained by the Standard Model.

(Source: livescience)

So now let’s go from apples to the Alps. Possibly the freakiest experiment in the history of science happened in a tunnel under the Alpine mountain range. All the theories in the Standard Model had a huge problem: all the equations would work only if the particles were massless, which we know is not the case. Peter Higgs proposed a model whereby the Universe has a special quantum field in which every particle moves and interacts, but still the 16 elementary particles did not give a whole picture. Mathematically, an element was missing: the Higgs boson, which provides an explanation for the cosmic connection.

The Large Hadron Collider (LHC) experiment is the largest single machine in the world, and an extremely complicated feat of human engineering. To put it in simple words, two hadron collider beams are allowed to smash head on at a speed higher than that of light using particle accelerators that are 17 miles long. Using measurements gained from these particle collisions, and Einstein’s Theory of Relativity, investigations can be carried out into new particles. However, these particles occur so rarely, in about 1/10 billion collisions, and also have an instantaneous decay of 10^-22 sec. A powerful supercomputer scrutinises each second of the collision, providing the data for the Higgs boson. It was finally hypothesised that the Higgs boson has an energy of about 1025 GeV and is 133 times mass of a proton.

This has begun a whole new era of Particle Physics, in which we are closer than ever before to understanding the laws of the Universe. We are very privileged to live in such an era, but the quest must continue, as the Standard model does not explain many important features of the known universe, such as: gravity, dark matter and dark energy.

#HiggsBosonParticle #Physics #HimaHaridevan

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