Rare boson particle ‘triplets’

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...

Preventing Our Universe From Collapsing

Physicists have proposed our universe might be a tiny patch of a much larger cosmos that is constantly and rapidly inflating and popping off new universes. In our corner of this multiverse, the mass of the Higgs boson was low enough that this patch did not collapse like others may have. (Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images)

The Higgs boson, the mysterious particle that lends other particles their mass, could have kept our universe from collapsing. And its properties might be a clue that we live in a multiverse of parallel worlds, a wild new theory suggests.

That theory, in which different regions of the universe have different sets of physical laws, would suggest that only worlds in which the Higgs boson is tiny would survive.

If true, the new model would entail the creation of new particles, which in turn would explain why the strong force — which ultimately keeps atoms from collapsing — seems to obey certain symmetries. And along the way, it could help reveal the nature of dark matter — the elusive substance that makes up most matter.

A tale of two Higgs
In 2012, the Large Hadron Collider achieved a truly monumental feat; this underground particle accelerator along the French-Swiss border detected for the first time the Higgs boson, a particle that had eluded physicists for decades. The Higgs boson is a cornerstone of the Standard Model; this particle gives other particles their mass and creates the distinction between the weak nuclear force and the electromagnetic force.

But with the good news came some bad. The Higgs had a mass of 125 gigaelectronvolts (GeV), which was orders of magnitude smaller than what physicists had thought it should be.

To be perfectly clear, the framework physicists use to describe the zoo of subatomic particles, known as the Standard Model, doesn't actually predict the value of the Higgs mass. For that theory to work, the number has to be derived experimentally. But back-of-the-envelope calculations made physicists guess that the Higgs would have an incredibly large mass. So once the champagne was opened and the Nobel prizes were handed out, the question loomed: Why does the Higgs have such a low mass?  READ MORE...

From the Dawn of Time

The particle was produced inside the Large Hadron Collider at CERN. (Image credit: Shutterstock)

Physicists at the world's largest atom smasher have detected a mysterious, primordial particle from the dawn of time.

About 100 of the short-lived "X" particles — so named because of their unknown structures — were spotted for the first time amid trillions of other particles inside the Large Hadron Collider (LHC), the world's largest particle accelerator, located near Geneva at CERN (the European Organization for Nuclear Research).

These X particles, which likely existed in the tiniest fractions of a second after the Big Bang, were detected inside a roiling broth of elementary particles called a quark-gluon plasma, formed in the LHC by smashing together lead ions. By studying the primordial X particles in more detail, scientists hope to build the most accurate picture yet of the origins of the universe. They published their findings Jan. 19 in the journal Physical Review Letters.
wie X particle's internal structure, which could change our view of what kind of material the universe should produce."

Scientists trace the origins of X particles to just a few millionths of a second after the Big Bang, back when the universe was a superheated trillion-degree plasma soup teeming with quarks and gluons — elementary particles that soon cooled and combined into the more stable protons and neutrons we know today.

Just before this rapid cooling, a tiny fraction of the gluons and the quarks collided, sticking together to form very short-lived X particles. The researchers don't know how elementary particles configure themselves to form the X particle's structure. But if the scientists can figure that out, they will have a much better understanding of the types of particles that were abundant during the universe's earliest moments.  READ MORE...

A New Force

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