Physicists from the European Center for Nuclear Research have discovered a new particle, the 80th in its history, whose properties will help test models of quantum physics, CERN announced on Tuesday.
This is “the first particle identified since the improvement work on the LHCb detector completed in 2023” and “only the second time that a baryon composed of two heavy quarks has been observed”, underlines Vincenzo Vagnoni, spokesperson for CERN in a press release.
“This result will help theorists test models of quantum chromodynamics”, the theory which describes the strong interaction, the fundamental force which ensures the cohesion of the nucleus of atoms, he continues.
All the matter we observe around us – including the protons and neutrons that make up the nuclei of atoms – is made of baryons, common particles made up of three quarks.
Quarks with different flavors
Up, down, charm, strange, top and bottom: there are six kinds (or “flavors”) of quarks which differ according to their mass, their electric charge and their quantum properties.
In theory, many types of baryons can therefore be formed by combining these “flavors”. But most are very difficult to observe, because they are very unstable.
To produce them, CERN’s accelerator, the Large Hadron Collider (LHC), smashes particles thrown against each other in a ring at phenomenal speeds. Unstable hadrons (baryons and mesons composed of two quarks) decay quickly. But the more stable particles produced during decay can be detected and their presence allows scientists to deduce the properties of the original particle.
The new particle has a structure similar to that of the proton, consisting of two “up” quarks and one “down” quark. But the “up” quarks are replaced by heavier “charmed” quarks, which gives it a mass four times higher than the proton.
In 2017, the LHCb collaboration announced the discovery of a very similar particle, composed of two “charmed” quarks and an “up” quark. The new particle has a predicted lifetime up to six times shorter, making it even more difficult to observe.
