In April, scientists outside the European Center for Nuclear Research, or CERN, Geneva, once again fired their cosmic gun, the Large Hadron Collider. After a three-year shutdown for repairs and upgrades, Collider has resumed shooting naked protons of protons – hydrogen atoms – around its 17-mile electromagnetic underground racetrack. In early July, the collision will cause these particles to start collapsing together to create a spark of primitive energy.
And so amidst new developments and the fresh hopes of particle physicists, the great game of hunting for the mysteries of the universe is about to begin again. Even before its renovation, the collision was producing signs that nature could hide something wonderful. Mitesh Patel, a particle physicist from Imperial College London who conducts an experiment at CERN, His previous run data has been described as “the most compelling set of results I’ve ever seen in my professional life”.
A decade ago, CERN physicists created global headlines with the discovery of the Higgs boson, a long-sought-after particle that powers all other particles in the universe. What’s left to find? Almost everything, says optimistic physicists.
When the CERN Collider was first launched in 2010, the universe was ready to capture. The largest and most powerful machine ever built to detect the Higgs boson. That particle is the keystone of the standard model, a set of equations that explain everything scientists are able to measure about the subatomic world.
But there are deeper questions about the universe that the standard model does not explain: Where did the universe come from? Why is it made of matter instead of antimatter? What is the “dark matter” that fills the universe? How does the Higgs particle itself have mass?
Physicists had hoped that some answers would come true when the Large Collider was first launched in 2010. Nothing appears except Higgs – in particular, there is no new particle that can explain the nature of dark matter. Disappointingly, the standard model remained unchanged.
The collider was shut down in late 2018 for extensive upgrades and repairs. According to the current schedule, the Collider will run until 2025 and then shut down for another two years to install other comprehensive upgrades. This set of upgrades includes improvements to the giant detector that sits at four points where the proton beam collides and analyzes the collision debris. Starting in July, those detectors will cut their work for them. The protons have been squeezed to intensify the beam, increasing the likelihood of protons hitting at the crossing point – but confusing for detectors and computers in the form of multiple sprays of particles that need to be separated from each other.
“Data will come at a faster rate than we used to,” said Dr. Patel said. Where at one time there were only two collisions at each beam crossing, now there will be more like five.
“It makes our lives harder in some sense because we have to be able to find the things that interest us in between all those different interactions,” he said. “But that means there’s a greater chance of seeing what you’re looking for.”
Meanwhile, various experiments have revealed potential cracks in the standard model – and hinted at a broader, more profound theory of the universe. These results include the rare behavior of subatomic particles whose names are unknown to most of us in Cosmic Bleachers.
Muon Low, a subatomic particle that briefly became popular last year. Muns are often referred to as fat electrons; They have the same negative electrical charge but are 207 times larger. “Who ordered?” Isador Rabi, a physicist, states that when Muns was discovered in 1936.
No one knows where the muons fit into the grand scheme of things. They are created by the collision of cosmic rays – and in the event of a collision – and they radically decay in microseconds into electrons and haunted particles called neutrinos.
Last year, a team of about 200 physicists affiliated with the Fermi National Accelerator Laboratory in Illinois reported that munitions moving in a magnetic field sank significantly faster than predicted by the standard model.
The discrepancy with the theoretical hypotheses occurred in the eighth decimal place of the value of the parameter named g-2, which describes how the particle reacts to the magnetic field.
Scientists have attributed the fractional but real difference to a quantum whisper of yet-unknown particles that will temporarily materialize around Muon and affect its properties. Confirming the existence of particles will, in the end, break the standard model.
But two groups of theorists are still working to reconcile speculations about what the G2 should be, while awaiting further information from the Fermilab experiment.
“The G2 anomaly is still very much alive,” said Ida X. Al-Khadra, a physicist at the University of Illinois who helped establish a consensus prediction in a three-year effort called the Muon G-2 Theory Initiative. “Personally, I am hopeful that cracks in the standard model will increase earthquakes. However, the exact position of the cracks can still be a dynamic target.
Munn also has a figure in other discrepancies. The main character in this play, or perhaps the villain, is a particle called B. quark, one of the six species of quark that forms heavy particles like protons and neutrons. B means beauty at the bottom or, perhaps, at the bottom. Such quarks occur in two-quark particles called B masons. But these quarks are unstable and are likely to deviate in a way that violates the standard model.
Some rare decays of B. quark involve a daisy chain of reactions, ending in a separate, lighter type of lightweight particle pair called quark and leptons, either electrons or their plump cousin, muon. The standard model assumes that electrons and muons appear alike in this reaction. (There’s a third, heavier lepton called a tau, but it crumbles too fast to be observed.) But Dr. Patel and his associates have discovered more electron pairs than muon pairs in violation of a principle called lepton universality.
“This could be a standard model killer,” said Dr. Patel, whose team is investigating B Quark with LHCB, a large detector of the Large Hadron Collider. This discrepancy, like the magnetic dissonance of muon, indicates an unknown “influencer” – a particle or force interfering with the reaction.
One of the most dramatic possibilities, if this data is retained in the next collider run, Dr. There is a subatomic speculation called leptocarc, Patel says. If a particle did exist, it could bridge the gap between the two classes of particles that make up the physical universe: lightweight leptons – also electrons, muons and neutrinos – and heavier particles like protons and neutrons, which are made up of quarks. There are six types of quark and six types of leptons.
“We are going into the race with more optimization that a revolution can come,” said Dr. Patel said. “Fingers crossed.”
There is yet another particle in this zoo that behaves strangely: the W boson, the so-called weak force responsible for radioactive decay. In May, physicists with a collider detector at Fermilab, or CDF, reported a 10-year effort to measure this particle mass, based on about 4 million W bosons harvested from collisions in Fermilab’s Tevetron, the world’s most powerful collider. Until the Large Hadron Collider.
According to the standard model and previous mass measurements, the weight of the W boson should be about 80.357 billion electron volts, which is the unit of mass-energy chosen by physicists. In comparison, the Higgs boson weighs 125 billion electron volts, which is equivalent to an iodine atom. But W’s CDF measurement, the highest ever, came at more than 80.433 billion. The experimenters calculated that 2 trillion – 7-sigma, in physical terms – was the only chance that this discrepancy was a statistical fluke.
The mass of the W boson is connected to a mass of other particles, including the infamous Higgs. So this new discrepancy, if it retains, could be another crack in the standard model.
Nevertheless, the three discrepancies and the theorists’ hopes for a revolution could evaporate with more data. But for optimizers, all three point in the same incentive direction towards hidden particles or forces interfering with “known” physics.
“So a new particle that could explain both the G2 and the W mass could be within the reach of the LHC,” said Kyle Cranmer, a physicist at the University of Wisconsin who works on other experiments at CERN.
John Ellis, a theorist at CERN and King’s College London, noted that at least 70 papers have been published indicating clarification for new W-Mass discrepancies.
“Many of these disclosures also require new particles that may be accessible to the LHC,” he said. “Did I mention Dark Matter? So, lots of things to keep in mind! “
From the next race, Dr. Patel said: “It will be exciting. It will be hard work, but we’re really looking forward to seeing what we’ve got and whether there’s really anything exciting in the data.
He added: “You can go through a scientific career and not say it once. So it feels like a privilege.”