The long road to the Higgs boson – and beyond
On 4 July 2012 CERN announced to the world that they had found what they believe to be the elusive ‘God Particle’, the Higgs boson. A day now known to physicists as Higgserpendance Day. The following day the front covers of newspapers did not have the usual politics, banking scandals or Kim Kardashian’s latest exploits, they were completely dedicated to this subatomic particle. What is the importance of this? Why would anyone care? What does it do?
I recently attended The Bakerian Medal and Lecture at The Royal Society, an award which started in 1775 by Henry Baker. It is the premier lecture in the physical sciences which is awarded yearly. This year it would be given by Professor John Ellis CBE FRS of Kings College London on his work at CERN and the Higgs boson, entitled, ‘The Long Road to the Higgs boson – and beyond’.
I had seen photos of John Ellis with Stephen Hawking, wearing t- shirts and chinos, long silver hair and big silver bushy beard and I thought ‘cool dude’. In person he does not disappoint, a larger-than-life character.
Professor Ellis received his PhD in theoretical particle physics from King’s College, Cambridge in 1971. His areas of interest focus on particle physics, astrophysics, cosmology, quantum gravity and lately the interface between particle physics and cosmology (particle astrophysics). He has held positions at the Stanford Linear Accelerator Centre and California Institute of Technology. He then moved to CERN, where he remains and maintains a joint position as the Clerk Maxwell Professor of Theoretical Physics at King’s College London. He has received awards including the Maxwell Medal and the Paul Dirac Prize, in 2012 he was awarded a CBE. He was awarded the 2015 Bakerian Medal and Lecture for his ground breaking work in the physics of the Higgs boson and his attempts at unifying the fundamental forces of nature through his work at the Large Hadron Collider (LHC).
After decades of searching, starting in 1964 by Peter Higgs, the discovery of the Higgs boson occurred at CERN’s LHC in 2012. This unique particle which is the signature of the origin of the masses of elementary particles. It completes the Standard Model describing all physical matter in the Universe.
After taking to the stage Professor Ellis thanked the audience for attending, and that it was his pleasure to be giving this lecture to us. Being humble with success is such a redeeming quality. He attempted to share what Higgs is telling us and what is beyond in the Universe and how one would go about finding it?
We know that matter contains molecules, these molecules contain atoms and atoms contain nuclei, which at the centre have electrons whizzing around, protons and neutrons, up or down quarks defining the protons and neutrons. What they are trying to achieve at the LHC is not only the physical properties of visible matter, but also of what the physical properties of the invisible, like Dark Matter, believed to having played a pivotal role in the formation of the galaxies.
During the 20th century experiments were carried out on cosmic rays, which contained charged particles with extremely high energies. It was through the experiments on these particles that phenomena such as anti-matter were discovered. As techniques progressed during the 20th century, if one were to work with these particles, they would need to be done so in a controlled manner using known beams of particles and known energies. Hence, particle accelerators were constructed. The experiments carried out revealed what is known as the Standard Model of particle physics. Experiments began to find new physical phenomena of the type that had been predicted with the Standard Model. During the 1980’s and 1990’s more detailed experiments were carried out, confirming predictions made by the Standard Model with extreme accuracy.
So what does this Standard Model consist of? It describes visible matter known in the universe. The nuclei of the visible matter, the quarks, electrons and heavier electron like particles such as muons. These particles are the basic building blocks of matter. Therefore, to build something, you have to stick these building blocks together. To understand the fundamental forces, such as gravitation, electro magnetism and the two other forces that act within the nuclei, the strong nuclear force that holds the nuclei together and the weak nuclear force that is responsible for radioactivity. These are what John Ellis likes to call the Cosmic DNA, encoding all information needed to make all the visible stuff in the universe.
One has to know where particle mass comes from? We know that weight is proportional to mass as told by Newton, Einstein told us that energy is related to mass in his famous equation. But unfortunately they did not tell us where this mass came from in the first place? They did not explain the origin of mass? This is where Peter Higgs comes in, his theory of where particle masses may come from. In his 1964 paper, he would predict the existence of the particle known as the Higgs boson. The basic idea was to postulate what physicists call a field, a sort of universal medium that extends throughout all of space. To be able to travel through the Higgs field, one would imagine that a massless photon would travel through this field at the speed of light without really interacting, just skimming through the field. Particles containing mass, such as an electron move more slowly, it will interact with the field, it is moving slower than the speed of light. A heavier particle with a large mass will move very slowly through the field and interact deeply.
The Higgs field is said to be similar to the electromagnetic field, always being constant and everywhere. It is this field in particular that may explain why particles have mass. It has been difficult to confirm that this field really exists, this being of importance to finding the Higgs boson particle. If one imagines this field as snow, quantum of this snow would be a snowflake. The quantum of this field is the Higgs boson particle. Of course not all snowflakes are the same, each one will have different composites of water molecules. Subsequently, will there be other formations of the Higgs boson particles? Having found one Higgs boson particle, the search now is to find others. The importance of finding this particle can confirm that the Standard Model was correct. What they discovered at CERN, was that the particle did behave, interact and decay in the manner that the Standard Model predicted.
In a pre-published paper John Ellis sent to a science publication, they said that they had, “without a doubt found the Higgs boson particle”. Of course the scientific journal replied with, no, no, no, you cannot claim that you have without a doubt found the Higgs boson particle. On 10 December 2013, Peter Higgs and Francois Englert won the Nobel Prize, with the Nobel Prize headline, that they had, “without a doubt found the Higgs boson particle”. It seems what was a no for a science journal, was fine for the Nobel Prize Committee.
Professor Ellis continues to work at CERN on the physics of the Higgs boson particle, and Dark Matter. However his primary work is Supersymmetry, which is an extension of the Standard Model that may predict a partner particle for each particle in the Standard Model, explaining why particles have mass.
By Darren Carty, second year student, BSc Honours Biological Sciences (Molecular Biology & Genetics)