On Sept. 10, scientists and citizens tuned in for the successful startup of what is being touted as the greatest experiment in particle physics: the Large Hadron Collider (LHC). Found underground at the CERN laboratories near Geneva, the world’s largest particle accelerator is the result of 14 years of collaborative efforts that bridged languages and nations, including contributions from several University of Toronto scientists.
“It’s a fantastic moment,” said LHC project leader Lyn Evans about the collider’s first successful particle steering. “We can look forward to a new era of understanding about the origins and evolution of the universe.”
Before entering the main particle accelerator loop, positively charged particles called protons are channeled through a series of circular paths, in which superconducting magnets increase their velocity. As the protons are shifted to larger and larger circular paths, they approach the speed of light. At this point, energy added through magnetic and electric fields makes the particles heavier. The final stage of the LHC channels these “heavy” particles into the main accelerator, an underground tube with a circumference of 27 kilometers, located at the France-Switzerland border. Once inside, the particles are split into two channels and travel around the final track in opposite directions. The collision of these two groups of high-speed particles occurs at unprecedented levels of high energy. The results of these collisions should allow scientists to discover the fundamental forces and particles that were at work in creating the universe.
The LHC hopes to validate the Standard Model, which according to U of T Physics Professor Robert Orr has “allowed us to understand the behaviour of the minute particles that make up matter.” While the Standard Model represents everything humans currently understand about particle physics, there are several phenomena left unexplained, including the origin of mass. It is thought that the “Higgs Mechanism” may be the answer, in which case a so-called Higgs boson particle would exist. The Higgs boson, occasionally referred to as the “God Particle,” is theorized to be the crucial link in explaining how matter has mass. This elusive entity has not yet been revealed by less powerful particle accelerators. U of T’s role in the LHC project is focused on the ATLAS (AToroidal Lhc ApparatuS) experiment, one of the goals of which is and attempt to find Higgs boson particles.
At an event held by the Department of Physics last week, U of T ATLAS team members revealed that preliminary data is promising. Dr. Richard Teuscher, an experimental physicist at U of T, works with the LHC at CERN. He indicated that the next step is studying the calorimetric component, which investigates the heat of reactions or any physical changes that occur.
While this initial startup is a monumental moment in history, Dr. Teuscher is quick to note, “We will need several years to find the needles in the haystack such as the Higgs boson.” Two to three years worth of LHC data will be required in order for scientists to make meaningful analyses about Higgs boson particles. Due to the relative low Higgs boson production rate, for every few hours the collider is running, scientists estimate that only one of these sought-after particles will be generated.
The first stage in unraveling the universe’s origins has already yielded positive results. The operational LHC gives a preliminary picture of what occurs during the time of collision. LHC collaborators point out that it will take several weeks to months for the particles to reach the critical speeds necessary to surmise creating the Higgs boson particle.
