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Pentaquark finally discovered

After 50 years of searching: the pentaquark, with four quarks and an antiquark

CERNAfter 50 years of searching: the pentaquark, with four quarks and an antiquarkCERN

An uncommon type of particle studied by physicists for at least 50 years was unexpectedly identified by researchers at Syracuse University in the United States, members of one of the research groups of the Large Hadron Collider (LHC) in Geneva, Switzerland.  Protons and neutrons – the building blocks of atoms, along with electrons – are made up of smaller particles called quarks.  Each proton and neutron is composed of three quarks.  Announced in July 2015 by the European Organization for Nuclear Research (CERN), home of the LHC, the newly discovered particle – called the pentaquark – is also a component of protons and neutrons.  The difference is that it contains five quarks, or rather, four quarks and an antiquark, whose electrical charge is opposite to that of “regular” quarks.  This was an unknown combination until now.  Quarks are particles that move almost at the speed of light.  Scientists had been searching for the pentaquark for at least 50 years, to no avail, making them think it might actually not exist.  Curiously, it was found when the researchers were pursuing completely unrelated research goals.  The study of pentaquarks, now more than just a theory, may expand existing knowledge about possible interactions between elementary particles of matter.