It’s been six years since physicists at Europe’s Large Hadron Collider announced the discovery of the Higgs boson, but they’re just now confirming what most of the mysterious subatomic particles do when they decay.
They’re transformed into bottom quarks, they announced today.
That’s not exactly a surprise: The mainstream theory of particle physics, known as the Standard Model, suggests that’s the most common course followed by the Higgs, which exists in the particle collider for only an instant before breaking down. About 60 percent of the Higgs bosons created in high-energy are thought to turn into a pair of bottom quarks, which is No. 2 on the mass scale for six “flavors” of quarks.
It took several years for researchers to nail down the evidence to a standard significance of 5-sigma — the same standard that applied to the Higgs boson’s discovery in 2012.
Experiments at Europe’s Large Hadron Collider have produced hard-to-come-by evidence of interactions between the Higgs boson and top quarks. The findings, announced today at a conference in Bologna, Italy, “give a strong indication that the Higgs boson has a key role in the large value of the top quark mass,” Karl Jakobs, spokesperson for the LHC’s ATLAS collaboration, said in a news release.
An experiment conducted deep underground in an old South Dakota gold mine has given scientists hope that a future detector could help solve one of physics’ biggest puzzles: why the universe exists at all.
Put another way, the puzzle has to do with the fact that the universe is dominated by matter.
That may seem self-evident, but it’s not what’s predicted by Standard Model of particle physics as currently understood. Instead, current theory suggests that the big bang should have given rise to equal parts of matter and antimatter, which would annihilate each other within an instant.
Scientists suspect that there must have been something about the big bang that gave matter an edge more than 13 billion years ago. So far, the mechanism hasn’t been identified — but one leading theory proposes that the properties of neutrinos have something to do with it.
The problem is, neutrinos interact so weakly with other particles that it’s hard to detect what they’re doing. The experiment conducted in the nearly mile-deep Sanford Underground Research Facility in South Dakota was aimed at figuring out whether a detector could be shielded well enough from background radiation to spot the effect that scientists are looking for.
An international team of researchers has detected a mysterious, previously unknown void deep inside Egypt’s Great Pyramid that may be as large as an art gallery space.
The anomalous space, known as the ScanPyramids Big Void, showed up on imagery produced by tracking concentrations of subatomic particles called muons as they zoomed through the pyramid’s stones.
“We don’t know if this Big Void is made by one structure, or several successive structures,” said Mehdi Tayoubi, president of the Heritage Innovation Preservation Institute and co-founder of the ScanPyramids campaign. “What we are sure about is that this Big Void is there, that it is impressive [and] that it was not expected, as far as I know, by any kind of theory.”
What happened to all the antimatter? A particle-smasher in Japan is well on its way to addressing that question and others on the frontier of physics.
The SuperKEKB accelerator is designed to smash together tightly focused beams of electrons and anti-electrons (better known as positrons) and track the subatomic particles that wink in and out of existence as a result.
The collider will follow up on an earlier round of experiments at the KEK laboratory in Tsukuba. Over the past five years, KEK’s 1.9-mile-round (3-kilometer-round) underground ring has been upgraded to produce collisions at a rate 40 times higher than the earlier KEKB experiments did. Europe’s Large Hadron Collider may smash protons together at higher energies, but SuperKEKB will trump the LHC when it comes to the “Intensity Frontier.”
On Feb. 10, scientists circulated a beam of positrons around the SuperKEKB ring at nearly the speed of light. Then, on Feb. 26, they sent a separate beam of electrons at similar velocities, but going in the opposite direction. These “first turns” serve as major milestones on the way to next year’s first physics run, when both beams will circulate simultaneously and smash into each other in SuperKEKB’s upgraded Belle II detector.
The Higgs boson is the biggest find of the century in particle physics, but for the past few weeks, physicists at the Large Hadron Collider have been considering whether there’s a mystery that’s even bigger. Or at least more massive.
The potential mystery has to do with a pattern of particle decay that results in the emission of two photons. The readings collected so far by the teams using the ATLAS and CMS detectors point to a slight “bump” in the expected pattern.
That may hint at the existence of a previously undetected particle with a mass of about 750 billion electron volts – six times heavier than the Higgs, French physicist Adam Falkowski (a.k.a. Jester) writes in his Resonaances blog.
Before the LHC’s startup in 2008, the Internet was set abuzz with worries that high-energy collisions could create globe-gobbling black holes or cosmos-wrecking strangelets. Protests were mounted, lawsuits were filed, and physicists at Europe’s CERN particle physics center had to explain in depth why the nightmare scenarios were nothing more than nightmares. Once the collider went into operation, the lawsuits were dismissed and the hand-wringing settled down.
Now the world’s largest collider is operating at near its design limits, and this week, CERN reported that lead-ion collisions in the LHC’s ALICE detectorreached energies beyond a quadrillion electron-volts – a level also known as 1 peta-electron-volt, or 1 PeV.
“This energy is that of a bumblebee hitting us on the cheek on a summer day. But the energy is concentrated in a volume that is approximately 10 -27 (a billion-billion-billion) times smaller,” Jens Jørgen Gaardhøje, professor at the Niels Bohr Institute at the University of Copenhagen and head of the Danish research group within the ALICE experiment, said in a news release.
At first blush, a quadrillion electron-volts sounds like a huge ramp-up from 13 trillion to 14 trillion electron-volts, or 13 to 14 TeV, the traditionally quoted figures for the high end of the LHC’s collision energy. That’s what set off the doomsayers. In the weeks leading up to the ALICE collisions, there was a drumbeat of postings claiming that “CERN LIED” and warning that 1-PeV smashups would have catastrophic consequences.