An extremely rare event in the world of particles has taken place during a Chinese-led study at the Large Hadron Collider (LHC) near Geneva, Switzerland.
And the event has scored yet another victory for the Standard Model – our current best theory to describe how the basic building blocks of the universe interact.
Sifting through experimental data collected between 2016 and 2018, researchers from Peking University and their colleagues from around the world spotted the simultaneous appearance of three force-carrying particles, known as bosons, which had never been seen together before. READ MORE...
Illustration of two types of long-lived particles decaying into a pair of muons, showing how the signals of the muons can be traced back to the long-lived particle decay point using data from the tracker and muon detectors. Credit: CMS/CERNThis search for exotic long-lived particles looks at the possibility of “dark photon” production, which would occur when a Higgs boson decays into muons displaced in the detector.The CMS experiment has presented its first search for new physics using data from Run 3 of the Large Hadron Collider. The new study looks at the possibility of “dark photon” production in the decay of Higgs bosons in the detector.
Dark photons are exotic long-lived particles: “long-lived” because they have an average lifetime of more than a tenth of a billionth of a second – a very long lifetime in terms of particles produced in the LHC – and “exotic” because they are not part of the Standard Model of particle physics.The Standard Model is the leading theory of the fundamental building blocks of the Universe, but many physics questions remain unanswered, and so searches for phenomena beyond the Standard Model continue.
CMS’s new result defines more constrained limits on the parameters of the decay of Higgs bosons to dark photons, further narrowing down the area in which physicists can search for them. READ MORE...
Preparations for a massive new particle smasher near Geneva are picking up speed. But the European-led project, which hopes to answer some of the biggest questions in physics, faces many obstacles, including competition from China.
In 2012 scientists at the European Organization for Nuclear Research (CERN) achieved a key breakthrough when they detected the elusive Higgs boson, an elementary particle that gives mass to all the others. This followed decades of work using accelerators such as the famed Large Hadron Collider (LHC), the world’s most powerful particle collider located north of Geneva.
Yet many fundamental questions about the universe remain unanswered: What constitutes dark matter? Why is our universe filled with matter and not antimatter? Or why do the masses of elementary particles differ so much?
The search for answers to these and other big physics questions requires another “leap to higher energies and intensities”, says CERN. The organisation wants to build a more powerful and precise successor to the LHC, which was conceived in the early 1980s and will complete its mission in 2040.
“We build these machines to explore the nature of the universe. It’s about going out into the unknown and exploring further,” says Mike Lamont, CERN’s director of accelerators and technology.
And so, following requests by the global physics community, plans for the so-called Future Circular Collider (FCC) have been taking shape over the past ten years. READ MORE...
The Large Hadron Collider (LHC) sparked worldwide excitement in March as particle physicists reported tantalizing evidence for new physics — potentially a new force of nature. Now, our new result, yet to be peer reviewed, from CERN’s gargantuan particle collider seems to be adding further support to the idea.
Our current best theory of particles and forces is known as the standard model, which describes everything we know about the physical stuff that makes up the world around us with unerring accuracy. The standard model is without doubt the most successful scientific theory ever written down and yet at the same time we know it must be incomplete.
Famously, it describes only three of the four fundamental forces – the electromagnetic force and strong and weak forces, leaving out gravity. It has no explanation for the dark matter that astronomy tells us dominates the universe, and cannot explain how matter survived during the big bang. Most physicists are therefore confident that there must be more cosmic ingredients yet to be discovered, and studying a variety of fundamental particles known as beauty quarks is a particularly promising way to get hints of what else might be out there.
Beauty quarks, sometimes called bottom quarks, are fundamental particles, which in turn make up bigger particles. There are six flavors of quarks that are dubbed up, down, strange, charm, beauty/bottom and truth/top. Up and down quarks, for example, make up the protons and neutrons in the atomic nucleus.
The LHCb experiment at CERN. Credit: CERNBeauty quarks are unstable, living on average just for about 1.5 trillionths of a second before decaying into other particles. The way beauty quarks decay can be strongly influenced by the existence of other fundamental particles or forces. When a beauty quark decays, it transforms into a set of lighter particles, such as electrons, through the influence of the weak force. One of the ways a new force of nature might make itself known to us is by subtly changing how often beauty quarks decay into different types of particles. TO READ MORE, CLICK HERE...
Harry Cliff, a Cambridge particle physicist writes...After years without particle physics making the news, recent announcements suggest a breakthrough. Could a new fundamental force also explain the mystery of the three generations of matter? Harry Cliff weighs up the case.
Most of my colleagues would probably admit, at least in private, that it’s been an anxious time to be a particle physicist. Thirteen years ago, when the world’s largest (and most expensive) scientific instrument, the Large Hadron Collider (LHC), fired up for the first time, hopes were high that we would soon discover new particles and forces that could help address some of the most profound mysteries in science.
Things got off to a spectacular start with the discovery of the long-sought Higgs boson in 2012, but momentous as its discovery was, the Higgs belongs to the well-established ‘standard model’ of particle physics, which took shape more than half a century ago in the 1960s and 70s. Now, I don’t want to do the standard model down. It is without a doubt the most successful scientific theory ever devised, describing everything we know about the fundamental building blocks that makes up the world around us with stunning precision. You could make a good case for it being the greatest intellectual achievement of humankind. But we know it can’t be the end of the story.
The standard model has no solutions for numerous thorny problems, including how matter survived annihilation during the Big Bang, or indeed why we observe the set of particles that we do. Perhaps its most glaring omission is its failure to account for a whopping 95% of universe, which astronomy tells us is dominated by enigmatic substances known as dark matter and dark energy. So, when the LHC switched on in September 2008, particle physicists like me were itching to see something altogether new, something that might show us the way to an expanded picture of the subatomic world.
Yet almost a decade later, after literally thousands of searches performed by the four big LHC experiments, nature has stubbornly refused to give up its secrets. After the discovery of the Higgs, the LHC experiments continued to verify the predictions of the standard model, while ruling out a whole host of speculative new theories that were intended to extend it into new territory.
Some began to talk about a crisis in particle physics. Could it be that the long quest for an ever-deeper understanding of the fundamental constituents of our universe had reached a dead end? However, amid the gathering gloom, a series of unexpected chinks of light were beginning to appear.
Once again, particle physics made headline news around the world. Major discoveries seemed to be arriving like buses.
The LHCb experiment, one of the four giant detectors that study particle collisions produced by the LHC and the experiment on which I work, was reporting a growing number of ‘anomalies’; measurements that seemed to be in tension with the predictions of the standard model. While intriguing, for a long while these deviations were too subtle for physicists to have much confidence that they were anything other than random statistical wobbles in the data. That is until the 23rd March of this year.
On that day, my colleagues at LHCb announced they had found firm evidence for exotic particles known as beauty quarks decaying in ways that the standard model can’t explain. If borne out, these results suggest the existence of a brand-new force of nature, which would make it arguably the most momentous scientific discovery of the 21st century so far. The story broke out into the mainstream media, quickly making it one of the most widely covered particle physics stories since the discovery of the Higgs in 2012.
Then, just two weeks later on the 7th April, a completely different experiment at Fermilab in the United States announced a second result that seemed to suggest that fundamental particles called muons were also experiencing the tug of a hitherto undiscovered force. Once again, particle physics made headline news around the world. Major discoveries seemed to be arriving like buses. READ MORE
