This past August, the University of Toronto hosted the 21st annual Hadron Collider Physics Symposium, where the first results of the Large Hadron Collider were presented and shared amongst particle physicists.
This year, the results included the reappearance of particles captured by previous particle accelerators, as well as evidence that the LHC can capture higher energy particles than expected. The event represents the obstacles overcome by LHC over the 20 years of its development — from vast feats of civil engineering, to firing up experiments that will hopefully explain the universe’s earliest stages.
The LHC is the world’s largest and most powerful particle accelerator (and fridge: the inside of the LHC is -271°C, making it colder than outer space). It is owned by CERN, the European Organization for Nuclear Research, and is located in Geneva, Switzerland. The LHC is a 27 km long underground tunnel, composed of two general-purpose detectors, CMS and ATLAS.
The detectors are essentially enormous cameras designed to take snapshots of particle collisions at a rate of 40 million frames per second. As for information flow, the amount of data collected by the LHC can fill 100,000 dual layer DVDs every year, solving the mystery of the relationship between physicists and caffeine. The LHC works by launching two beams of protons (or “hadron” particles) at 99 per cent the speed of light, 24 hours a day, seven days a week, and — you guessed it — smashing them to analyze the resulting particle decay.
These high precision proton beams are monitored around the clock by scientists such as U of T physics Professor William Trischuk, a TRIUMF scientist and ATLAS team member. The beams inside the accelerator must be controlled so that they do not stray and cause damage to the device. In fact, it is crucial that precautions are taken for any part of the LHC, because technical problems can delay the operation for months. One such incident occured in 2007 with a broken magnet, and again in 2009 when scientists discovered vacuum leaks.
The results from the LHC are significant to the study of physics because there are many contentious issues that lie unresolved regarding the make-up of the fundamental building blocks of the universe. What we learn from the LHC may very well confirm or destroy the Standard Model of Particle Physics, the current model of the elementary particles that make up all matter.
To give you an idea of what’s at stake, replacing the Standard Model of Particle Physics is probably harder than doing a decathlon, learning Icelandic, and sitting through Gigi. If that’s not enough, throw in river dancing and completing a degree in Engineering Science. All before breakfast.
A hot topic that comes to mind when people think of the LHC is the Higgs boson particle. The Standard Model has already gone through many trials testing the kinds of particles that constitute it: leptons, quarks, and the force carriers (such as the photon). However, the mass of these particles, especially the Z boson and W boson, relies on the Higgs boson as the key to the origin of particle mass.
According to U of T Professor Pierre Savard, a TRIUMF scientist and ATLAS team member, the Higgs boson is not made up of anything. It is the simplest particle with no spin and no electric charge.
An interesting detail about the Higgs boson is that it generates a Higgs Field. John Ellis of CERN describes the Higgs Field as analogous to a field of snow in which heavy particles that travel through the Higgs Field leave a bigger imprint than lighter particles do. The reason why some particles are heavier than others is simply due to how much they interact with the Higgs Field.
Despite this and other captivating images the Higgs may generate, it is important to keep in mind that the Higgs boson is not the sole answer to the origins of the universe and life itself. The coining of the Higgs as the “God Particle” by Leon Lederman, director of Fermilab, unintentionally creates a misconstrued perception of the Higgs in the mass media.
As experimental high-energy physics professor and ATLAS team member Robert Orr confirms, this colloquial definition of the Higgs is not very descriptive of what the Higgs really is. The Higgs may have “god-like” power in confirming or disconfirming the Standard Model, but it is not scientifically accurate to assign it an alias with religious connotations.
According to Professor Trischuk, “Finding the Higgs boson will confirm the Standard Model of Particle Physics as an accurate description of the universe — or at least until the model starts to break down before the precise moment of the Big Bang.” The Higgs theory will work until it is falsified using the LHC. And so for now, the Standard Model currently holds. However, a good example of an LHC-tested and disproved theory was that Earth had magnetic monopoles.
There are many exciting and terrifying conclusions that will result whether or not the Higgs is proven. If the Higgs is found, physicists will have to continue to better understand the nature of the Higgs and its ability to explain particle mass. But there are many theories that might remain unanswered, such as gravity, which continues to puzzle physicists.
It is also unknown whether the discovery of the Higgs will solve the great problem of missing mass and dark energy in the universe. Even if the Higgs is found, it will be some time before scientists are certain that it is a fundamental particle.
As Professor Savard points out, it is still not clear if quarks are fundamental particles. Quarks are point particles, meaning that physicists cannot see what is going on inside them. “For now the quark is a point particle, but we are not sure if it is fundamental,” says Professor Savard. “Looking at the history of particle physics, we see changes from the atom to the proton and neutron, and so on. So there is still a chance that the Higgs may be made up of more particles.”
Although it is very unlikely the Higgs will be found in the near future, this may be good news for busy particle physics professors. “If we find the Higgs, then I need to write new lectures,” jokes Professor Savard.
Given the question of what he believes students should take away from the LHC, Professor Savard replies that students may benefit from expanding their minds to harness the relationship between the “infinitely small to the infinitely big” in our universe.
Professor Orr eloquently adds that students can learn to appreciate the way the universe is “subtle, beautiful, and we’re only starting to learn how it works.”
