Scientists at the Large Hadron Collider have announced the discovery of the pentaquark, a class ofsubatomic particle consisting of four quarks and one antiquarkbound together. Like the Higgs boson before it, the pentaquark’sexistence has been theorized for years, but experiments in theearly-2000s claiming to have detected the exotic form of matterwere later invalidated. Many scientists had since given up on thepentaquark for good, but this time, say CERN physicists, there’s nodoubt it’s been found.
As its name suggests, the pentaquark is a particle consisting offive quarks bound together. Quarks are elementary particles thatexist in six variations known as flavors (these are given theunusual names of up, down, strange, charm, top, andbottom). These bind together in different combinations to forma range of composite particles, of which the most commonly knownare neutrons and protons, consisting of three quarks each.
“THE PENTAQUARK… HAS NEVER BEEN OBSERVED BEFORE INOVER 50 YEARS OF EXPERIMENTAL SEARCHES."
“The pentaquark is not just any new particle," said Guy Wilkinson, a spokesperson for the LHCb, one of theLHC’s seven particle detectors and the site of the pentaquark’sdiscovery. “It represents a way to aggregate quarks… in a patternthat has never been observed before in over 50 years ofexperimental searches. Studying its properties may allow us tounderstand better how ordinary matter, the protons and neutronsfrom which we』re all made, is constituted."
The discovery was made by watching the decay of a type ofsubatomic particle known as the Lambda B baryon. The data forthe resulting paper (which has beensubmitted for publication in the journal Physics ReviewLetters) was recorded between 2009 and 2012, butscientists were wary of the results given previous invalidated experiments. “We were studying something elseat the time so at first we ignored it," LHCb physicist SheldonStone told Nature. “For historicalreasons we were quite haunted by the word pentaquark, so we didevery conceivable check we could."
Some scientists have suggested thatthere may yet be a better interpretation for the data that does notinvolve pentaquarks, but CERN’s physicists are certain."Benefitting from the large data set provided by the LHC, and theexcellent precision of our detector, we have examined allpossibilities for these signals, and conclude that they can only beexplained by pentaquark states," said LHCb physicist TomaszSkwarnicki.