Faster, better, stronger.
A new phase of operations at the Large Hadron Collider – the world’s largest particle accelerator – is set to begin in a few weeks, just a day after the 10th anniversary of its greatest achievement to date: the discovery of the long-sought Higgs boson. .
The reopening of the collider (it has been closed since 2018) is an important event for global science, as what is generally considered to be one of the greatest scientific experiments ever conducted has already revealed important details about the fabric of the reality.
Higgs’ discovery in July 2012 confirmed the Standard Model of particle physics, which still dominates as the best explanation of how matter works. But scientists hope the latest LHC run will explain even bigger mysteries of existence, including the invisible particles that make up dark matter, and why there’s anything here.
“We are now ready for Run 3,” said Rende Steerenberg, who leads beam operations for CERN, the international organization that runs the LHC – a vast, hidden ring of tunnels and detector caverns built deep beneath the rocks. fields, trees and cities on the LHC. border between France and Switzerland, more than 8 km wide and more than 25 km around.
The LHC has been idle for more than three years as it has been upgraded with tens of millions of dollars worth of upgrades – the upgraded facility will reach energies of up to 13.6 trillion electrons – volts (TeV), up from just 13 TeV in the previous run – and advanced detection equipment to better examine the chaotic explosions inside the giant atom breaker. It is currently being tested at low power and the first experimental collisions of the third series will begin on July 5.
The LHC uses giant magnets to accelerate beams of protons and atomic nuclei in opposite directions around the underground ring, then brings them together for a series of high-energy collisions at nearly the speed of light. This makes it possible to reach energies that have not been seen since the first fractions of a second in the universe after the Big Bang.
Studying the remnants of such collisions can tell scientists what particles formed there, even for a tiny fraction of a second. Scientists believe that the thousands of collisions made inside the LHC every hour will produce at least some of the exotic particles they seek.
Steerenberg explained that the latest LHC upgrade is half a step before better detection methods are installed after 2027, when the LHC will operate at full capacity as a “high-luminosity” LHC – its fourth and final. incarnation before an even larger particle accelerator, the Future Circular Collider, is online after 2040.
The LHC is a crucial tool for physicists. Several unresolved problems remain in the theories intended to explain physical reality – some of which date back to the early 20th century – and scientists have suggested a variety of ideas about how it all fits together. Some of these ideas work on paper, but require the existence of certain particles with particular qualities.
The LHC is the most advanced particle accelerator built to date. It was designed to search for these particles and measure them. The results are integrated into the Standard Model which describes all known particles (there are currently 31, including the Higgs boson) and three of the four known fundamental forces: the electromagnetic force, the strong nuclear force and the weak nuclear force, but not gravity.
As well as enabling even more precise measurements of the particles that make up all the matter we see, scientists believe the upgraded LHC can help resolve several recently reported Standard Model anomalies.
One of the most puzzling is a discrepancy in the decay of the B meson, a transient particle made up of two types of quarks – the subatomic particles that make up protons and neutrons.
According to the theory, B mesons should decay into electrons and muons – a related class of subatomic particles – with equal rarity. But experiments show that B mesons decay into electrons about 15% more often than they decay into muons, said particle physicist Chris Parkes, who leads the Large Hadron Collider Beauty (LHCb) experiment.
LHCb takes its name from the ‘beauty’ quark which figures prominently in the study of the differences between matter and antimatter experiment (quarks can also be classified as ‘truth’, ‘up’, ‘down’ “, “charming” or “strange”, depending on their characteristics).
Equal amounts of matter and antimatter should have annihilated in the first moments of the Big Bang, but that clearly didn’t happen: instead, matter predominates, and the LHCb experiment aims to find out why. .
The reported anomaly in the decay of B mesons is related to this question, Parkes said, and the new LHC run could provide insight into the reasons for the anomalous decay.
“There are a lot of different metrics out there and, oddly enough, a number of them are pointing in the same kind of direction,” he said. “But there is no ‘smoking gun’ – rather it is an intriguing image that has been seen over the past few years.”
Another notable anomaly concerns the mass of the W boson, a subatomic particle involved in the action of the weak nuclear force that governs certain types of radioactivity.
The Standard Model predicts that W bosons have a mass of about 80,357 million electron volts, and this figure has been verified in several particle accelerator experiments.
But a series of precise experiments at Fermilab’s massive Tevatron particle accelerator near Chicago suggests instead that the W boson weighs a little more than it should – and that it could simply indicate “new physics” at the moment. beyond the standard model.
Particle physicist Ashutosh Kotwal, a professor at Duke University in Durham, North Carolina, who led the research at Fermilab that reported the discrepancy earlier this year, thinks it could be caused by a refinement of the model standard called “supersymmetry”, for which there is no solid evidence so far.
Kotwal is also a researcher at the LHC, and he hopes his improved version can verify that supersymmetry is more than just an idea. “It is possible that the W boson detects the existence of supersymmetric particles,” he said.
And if supersymmetry turns out to be a principle of the universe, it could explain several other mysteries – like the nature of the ghostly “dark matter” particles that many physicists believe make up about three-quarters of all matter in the universe. .
Although the gravity of dark matter particles explains the structure of galaxies, the particles themselves have never been seen and physicists cannot yet explain what they might be.
“If we look for indications of this particle directly at the LHC, it would be a manifestation of potential supersymmetry and it would be a manifestation of dark matter at the same time,” Kotwal said. “That’s the kind of stuff I push for.”