Large Hadron Collider scientists discover three new ‘exotic’ particles

The first-ever observations of a new 'pentaquark' and the first pair of 'tetraquarks'.
Chris Young
A section of the Large Hadron Collider.xenotar/iStock

Scientists at European nuclear research center CERN discovered three never-before-seen subatomic particles while working with the Large Hadron Collider, which was only recently turned back on following maintenance, a press release reveals.

The CERN scientists made the discovery of a new type of "pentaquark" and the first-ever pair of "tetraquarks" on Tuesday, July 5, adding to the illustrious list of new hadrons first observed at the 27-kilometre-long (16.8-mile) LHC.

New subatomic particles join the party

Ten years ago, scientists at the LHC found the Higgs boson particle, also known as the 'god particle', which is thought to have played a vital role in the early formation of the universe. 

Now, the new subatomic particle discoveries will help physicists better understand the way in which quarks bing to form composite particles. "Finding new kinds of tetraquarks and pentaquarks and measuring their properties will help theorists develop a unified model of exotic hadrons, the exact nature of which is largely unknown," said LHCb spokesperson Chris Parkes. "It will also help to better understand conventional hadrons."

Large Hadron Collider scientists discover three new ‘exotic’ particles
An illustration of the new pentaquark, made up of a charm quark and a charm antiquark and an up, a down, and a strange quark. Source: CERN

Quarks are elementary particles that combine, most often in twos and threes, to form hadrons, such as protons and neutrons. Rarely, quarks bind into larger combinations such as four-quark, five-quark particles, tetraquarks, and pentaquarks.

Large Hadron Collider scientists discover three new ‘exotic’ particles
An illustration of the pair of new tetraquarks. The one on the left is made of a charm quark, a strange antiquark, and an up quark and a down antiquark, and the one on the right is made up of a charm quark, a strange antiquark, and an up antiquark and down quark. Source: CERN

"The more analyses we perform, the more kinds of exotic hadrons we find," physicist Niels Tuning explained in CERN's statement. "We're witnessing a period of discovery similar to the 1950s, when a 'particle zoo' of hadrons started being discovered and ultimately led to the quark model of conventional hadrons in the 1960s. We're creating 'particle zoo 2.0'."

The LHC will likely make many more discoveries before 2025

The LHC, the world's largest physics laboratory, first started up in 2008 and a massive batch of collisions observed between 2010-2013 provided the first evidence of the Higgs boson particle. Since then, the collider has been responsible for the discovery of 66 hadrons.

In March this year, CERN announced it was ceasing collaboration with Russian scientists following Russia's invasion of Ukraine. In April, after three years offline due to routine maintenance and Covid delays, the LHC fired up once again, before almost immediately breaking a new record. In preparation for its third run of experiments, the particle accelerator created the most energetic beams of protons ever made by humans, with an energy of 6.8 trillion electronvolts (TeV).

For its current run, the LHC is expected to operate until another scheduled shutdown between 2025 and 2027. The drastically energized beams of protons will cause more collisions which, in theory, will allow for more new discoveries. Aside from studying interactions that are relevant to the very distant past, CERN is also looking to the future with plans for a successor to LHC, the even-larger €20 billion ($21.9 billion) Future Circular Collider. That, as well as the LHC's upcoming experiments, could help unlock many of the universe's secrets, including the mysterious force of dark matter.

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