Tag: Quarks

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LHC spots exotic particles — and starts hunting for more

Pentaquark illustration
A new type of pentaquark is shown as a pair of standard hadrons loosely bound in a molecule-like structure. Credit: CERN

Physicists say they’ve found evidence in data from Europe’s Large Hadron Collider for three never-before-seen combinations of quarks, just as the world’s largest particle-smasher is beginning a new round of high-energy experiments.

The three exotic types of particles — which include two four-quark combinations, known as tetraquarks, plus a five-quark unit called a pentaquark — are totally consistent with the Standard Model, the decades-old theory that describes the structure of atoms.

In contrast, scientists hope that the LHC’s current run will turn up evidence of physics that goes beyond the Standard Model to explain the nature of mysterious phenomena such as dark matter. Such evidence could point to new arrays of subatomic particles, or even extra dimensions in our universe.

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What happens to Higgs bosons? Here’s a clue

Higgs boson decay
A diagram shows a proton-proton collision in the Large Hadron Collider’s ATLAS detector that produced a Higgs boson, which quickly decayed into two bottom quarks (bb, shown as blue cones). The collision also produced a W boson that decayed into a muon (μ) and a neutrino (ν). (ATLAS / CERN Graphic)

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.

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Electron ion collider gets thumbs up from experts

A report from the National Academies endorses the idea of building a large-scale electron ion collider to probe the next level of subatomic mysteries. Such a collider would smash electrons into beams of protons or heavier ions — in contrast with the Large Hadron Collider, which smashes protons together.

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