Physicist recalls witnessing Higgs particle's discovery at CERN

Theoretical physicist who was at CERN the day Higgs particle was found ponders its meaning for mankind and for pure research

PUBLISHED : Sunday, 13 October, 2013, 12:00am
UPDATED : Monday, 14 October, 2013, 9:20am

About five years ago, during one of my many scientific visits to the European Centre for Nuclear Research ( CERN), the Large Hadron Collider (LHC) was officially turned on. I still have vivid memories of that day: I was in the main auditorium of CERN along with other scientists, eagerly awaiting that historic moment. The atmosphere was somewhat similar to the opening of the Olympics. While the Olympics are held every four years, many scientists have been longing for that moment for decades. Many of their careers hinge on the success of this experiment. The tension and excitement in the air was palpable.

Undoubtedly, the LHC is the world's largest and the most complex experiment. The LHC is large in every sense of the word, and a true exemplar of "big science". To get a sense of scale, here are some numbers. The project took more than 30 years from conception to completion. It is a collaborative effort of nearly 10,000 scientists and engineers from more than 100 countries, many have dedicated their careers to this project for decades.

The LHC, located in the border of Switzerland and France, is a huge particle accelerator. The circular tunnel of the LHC is approximately 27 kilometres in circumference and 100 metres underground.

Inside the accelerator, protons (particles that make up the nucleus) circulate around at nearly the speed of light. With this incredible speed, proton beams going in opposite direction undergo millions of collisions in the blink of an eye. It is from the results of these complex collisions that physicists try to infer the underlying laws of the universe.

The situation is similar to analysing the cause of a chain traffic accident from the debris left by the violent collisions, but with immensely more difficulty. One can imagine the engineering and technical problems that need to be faced. Thus we see that although the starting point of basic science research is not about practical use, the problems researchers encountered along the way often drive the development of applied technology.

The worldwide web is an example of such byproducts of basic science. It was invented because particle physicists need to share and transfer huge amount of data with scholars around the world.

To understand why scientists would devote their lifelong effort to carry out this arduous experiment, let us start with the Higgs boson (commonly known as the "God particle"). Half a century ago, theoretical physicists had already postulated that the presence of this particle can unlock the secret of the origin of mass.

What exactly is the Higgs particle? I believe we all have the following experience. When you take a dip in the water, you find it more difficult to move than on land because of the water resistance.

If you do not know that you are in water, you might have thought that you had mysteriously gained weight. In the early 1960s, Peter Higgs, Francois Englert and the late Robert Brout, along with a number of theoretical physicists, made a rather bold suggestion: if the entire universe is filled with an invisible "field", like a fish that has never left the ocean. We do not know that the resistance we feel is due to us living in the "Higgs ocean".

This resistance can be understood as the origin of mass. Just as different types of fish encounter different degrees of water resistance, different elementary particles constituting the universe (such as electrons and photons) feel the Higgs field differently, and thus have a different mass. For their work, Higgs and Englert shared this year's Nobel Prize in physics.

Since the Higgs field is the same everywhere in space, how do we know it actually exists? If you were a fish in a calm ocean, you could not tell whether or not you were living in a sluggish medium. The situation is different in turbulent water. Consider this analogy: if the protons running in the opposite directions within the LHC are two high-speed submarines, the water specks they create upon collision are the long-sought-after Higgs particles.

In other words, if the Higgs field is a vast ocean, the Higgs particle is a tiny water speck that constitutes this ocean! Producing a "Higgs speck" requires a lot of energy, and this is one of the reasons the LHC experiment is challenging.

On July 4 last year, two independent teams of CERN's LHC researchers (Atlas and CMS) officially announced the discovery of a Higgs particle. I happened to be at CERN at that time to give a talk and was fortunate to witness the unveiling of this scientific revolution.

As a theoretical physicist, I was particularly pleased to see that this experimental result once again proved that theoretical work is not just speculative. The Higgs particle is an important clue to understanding the cosmic blueprint, but scientists believe that it is likely just the first of many exciting discoveries to come. Cosmological data indicates that ordinary matter makes up only a small fraction of the universe; the rest is unknown, something we refer to as "dark matter" and "dark energy".

In light of these exciting prospects, three universities in Hong Kong joined forces early this year to establish a Joint Consortium for Fundamental Physics.

In the last century, research driven purely by scientists' curiosity to understand the microscopic world led to the discovery of quantum physics. Today, results from this basic scientific research has provided the necessities of our lives, such as mobile phones and computers. It is not inconceivable that research in particle physics today will bring us a better tomorrow.

Gary Shiu is chair professor of physics at Hong Kong University of Science and Technology

Watch: Prof. John Ellis of CERN tells The Post a Higgs boson joke and more.


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