Topic 2 – When the Goal is a Physics Discovery

 

Speaker: Dr. Archana Sharma (Senior Scientist at the Department of Physics at CERN)

 

What is the universe made of?

 

Dr. A. Sharma said that CERN studied the elementary building blocks of matter and the forces that controlled their behaviour, all of which fitted together in a model known as the Standard Model. She drew attention to the fundamental forces of nature on which life was dependent, namely electromagnetism, the strong nuclear force, the weak nuclear force and gravity. All of those forces together were what made the sun shine, for example.

The work of CERN was about recreating the conditions of the Big Bang to improve our understanding of the universe. CERN did so with the help of experimental information from telescopes, which provided a view of the universe far away in time and space, as well as through the use of accelerators, including the Large Hadron Collider (LHC).

 

The Large Hadron Collider (LHC) :

 

The LHC consisted of a 27 km ring along which counter-rotating beams of protons were made to collide. The collisions produced particles that were likely to have been present during the Big Bang. Some of the particles were highly expected while others were unsuspected, hypothetical or even extinct. For example, the Higgs boson particle had been a theory for many years before its actual discovery.

In line with the equation E = mc2, it was possible to observe that the energy generated in a collision converted into mass. It was the Higgs boson that gave mass to other particles by triggering electro-weak symmetry breaking. With enough energy, a Higgs boson could be produced in a collider. The theory behind the Higgs boson had been first advanced in 1964 by Francois Englert, Robert Brout, Peter Higgs, Gerald Guralnik, Carl Hagen and Tom Kibble. However, it had remained undiscovered for many years after.

The LHC had been built with the precise goal of discovering the Higgs boson. The project had a number of components: (1) accelerators; (2) detectors; (3) computing; and (4) collaborative science on a worldwide scale. Accelerators were powerful machines that accelerated particles to extremely high energies and brought them into collision with other particles. Detectors were gigantic instruments that recorded the resulting particles as they “streamed” out of the point of collision. Computing was needed to collect, store, distribute and analyse the vast amount of data produced by the detectors. The data had enabled pattern recognition and allowed scientists to predict the probable mass of the Higgs boson. Lastly, due to the scale of the LHC project, huge international collaboration was required across many different sectors. There were many people involved, including scientists, engineers, technicians, software engineers, financial advisors and lawyers.

 

The LCH as an extraordinary machine :

 

The LHC itself was the largest piece of scientific apparatus on the planet and many challenges were involved in its operation. For instance, the equipment needed to be kept at 1.9 degrees Kelvin, which was colder than the empty space in the universe. As much as 20–30,000 amperes of energy were required to get the protons moving and it had been difficult to create a cable that could carry a current so large (many conductors, such as copper, would burn). There had also been a need to create a vacuum so that the protons could move at all. Lastly, the collisions were happening 40 million times per second which made it challenging to collect data, including pictures.

 

The Higgs hunters :

 

ATLAS and the Compact Muon Solenoid (CMS) were the two detectors of the LHC designed to detect the Higgs boson as well as any other unexpected particle. They used completely different technology but were working towards the same goal. The detectors were electronic and worked by converting radiation into human-accessible form. For example, the CMS took digital pictures of the different particles created in a collision. Pictures were taken in every single direction so that no data was missed. Thanks to an in-built algorithm, it was possible to quickly sort through the pictures and make cuts based on their relevance. Thus, 40 million collisions could be reduced to about 1,000.

There had been many challenges involved in building the detectors. For instance, some parts were so huge that it had been difficult getting them on site. The enormous size of the detectors as a whole had also made them hard to operate.

Human resources from around the world were needed to make the LHC project a reality. Currently, CMS had around 6,288 people actively working on it, including 3,394 physicists, of which 1,228 were students, 1,102 engineers and 282 technicians from across 57 countries and regions.

 

Challenges in detecting the Higgs boson :

 

The Higgs boson had been difficult to detect for a number of reasons. First, it was not produced in every collision. Second, if it was produced, it was very unstable and would immediately start to decay into other particles. As such, the probability of “catching” it was one in a billion. Despite those difficulties, the Higgs boson had finally been discovered in 2012 by the ATLAS and CMS detectors – 48 years after the theory had been first advanced and two years after the detectors had been put into operation. The fact that both detectors had seen it had confirmed the discovery.

The discovery of the Higgs boson had been a very exciting, celebratory moment for the world, especially for CERN, and a giant leap forward for physics. The project had also been an example of the power of collaboration. It had shown that addressing problems collaboratively, believing in each other, and forgiving each other for mistakes could lead to great things.

 

Social impact :

 

There was now a question of what the future held for CERN. Some ideas included experiments on dark matter or antimatter. In addition, CERN technologies were being used in projects all over the world. Detectors had, for instance, been installed within the Egyptian pyramids where a void had been discovered. CERN also worked closely with primary schools hoping to encourage young, diverse people to enter the field.

The work of CERN could not only have a social impact but would also benefit business, industry and many other fields. A such, it was important to raise awareness about its scientific research and cutting-edge technology.