HIGGS FORCE
by Nicholas Mee

Physics is the new Rock ‘n’ Roll, apparently. And everyone wants to know what the Higgs boson is. So, what is it, where does the name come from and why is it sometimes called the God Particle? The first part of the name is easy to explain. It derives from the name of British theorist Peter Higgs who first dreamt it up in 1964. It is a boson, because this is what physicists call particles that transmit a force. (Boson derives from the name of the Indian physicist Satyendra Nath Bose who sent Einstein a paper discussing such particles in the early 1920s.)

It could be argued that the term God Particle arose because the Higgs boson plays such an important role in creating the intricate universe in which we live, and there is some truth in this. The world around us is filled with a multitude of complex and beautiful objects. We are surrounded by trees, galaxies, water droplets, volcanoes, ant colonies, mobile phones, rock bands and an endless array of other marvellous objects. All of which are the product of the subtle interplay of a small number of particles and forces, and the Higgs boson plays a critical role in ensuring that the forces have just the right properties to make the universe so complex and interesting.

Modern physicists understand the working of these forces very well. For instance, they know how the stars shine, they understand what matter is composed of and, quite remarkably, they even know how atoms were created. By the middle of the 20th century, everything could be attributed to the working of just four fundamental forces. Two of them – gravity and electromagnetism – are very familiar to us. Gravity holds us to the ground. Electromagnetism gives us the electricity that powers our guitars and synthesizers. But electromagnetism also holds atoms together. Atoms are composed of negatively charged electrons bound to a positively charged nucleus. When we delve even deeper, we find that the nucleus is a collection of particles known as protons and neutrons, bound together by a third force – the strong force. By contrast the fourth force is extremely feeble, it is known as the weak force.

Each force has its role, but the weak force is rather special, because it can transform one particle into another. In particular, it changes protons into neutrons and neutrons into protons. When this takes place in the nucleus of an atom, the atom is converted into a different atom and this is what happens in stars. A star, such as the sun, is just a huge ball of hydrogen that is gradually being converted into helium, with a steady release of energy. It is very important for us that the weak force is so weak, because this means that it will take the sun around ten billion years to convert all its hydrogen into helium. If the weak force were as powerful as the electromagnetic force, then it would all be over in the blink of an eye, or at least much less time than it would take for an eye to evolve.

This is where the Higgs particle comes in. Physicists now believe that the electromagnetic and weak forces are really two faces of a single force known as the electroweak force. The effect of the Higgs is to split what is ultimately one force into two very different ones. The idea is that the whole of space is filled with the Higgs field and that other particles find this background field sticky and become hindered as they move through it, with the result that they become heavy. But not all particles feel the Higgs Force; the ones that don’t just carry on zipping along unaffected. Critically, these include the bosons that transmit the electromagnetic force. They remain massless, and so electromagnetism remains powerful and long range. (Incidentally, these bosons are the fundamental particles from which light is formed. Physicists call them photons.) The bosons that transmit the weak force, on the other hand, become very heavy, with the result that the weak force is incredibly weak and extremely short range.

Despite the obvious importance of the Higgs boson – we wouldn’t be here without it – physicists feel rather uncomfortable about the term The God Particle. It originated as the title of a book published in 1993 by the Nobel Prize winning American physicist Leon Lederman. His book aimed to boost support for a particle collider called the Superconducting Supercollider (SSC) that was under construction in Texas. Unfortunately, the SSC, which would have been even more powerful than CERN’s Large Hadron Collider, was cancelled, leaving Texas with a two billion dollar hole in the ground, and physicists with the embarrassment of Lederman’s nickname for the Higgs.

The CMS Detector at the LHC. (Copyright CERN, Geneva)

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