New particle discovered at CERN is a long-lived double charmer
Physicists at CERN have discovered an exotic new particle that’s quite charming. Known as Tcc+, the particle belongs to a rare class called tetraquarks, and its unusual composition makes it the longest-lived exotic hadron found so far.
Matter is made up of fundamental particles called quarks, which come in six “flavors”: up, down, strange, charm, top and bottom. These quarks group together in different ways to make up different types of matter – baryons like protons and neutrons are made up of several quarks, while mesons are formed from quarks paired with antiquarks, their antimatter equivalents.
Baryons are usually comprised of two or three quarks, but exotic baryons made up of four or five have been discovered in recent years, after being theorized for decades. Tcc+ is one of these unusual particles with four quarks, known as a tetraquark.
The new particle contains two charm quarks, an up antiquark and a down antiquark. That makes it particularly exotic, the team says. When quarks and antiquarks pair up they usually do so within their own flavor: i.e., a charm quark with a charm antiquark. But this the first particle found to have charm quarks that aren’t countered with their own antiquarks. That makes Tcc+ what the researchers call “double open charm.”
Even more intriguing is the mass differences – charm quarks are considered heavy, while the up and down antiquarks are light. The mismatched masses essentially slow down the decay process of the particle, making it more stable. In fact, Tcc+ is the longest-lived exotic hadron known.
But it might not hold that record forever. The team says that the discovery suggests that another similar particle could be even more stable. If one or both of the charm quarks were swapped out for bottom quarks, the particle would last several orders of magnitude longer.
In the meantime, scientists will continue to study the new Tcc+ particle to see what other secrets it might unlock.
The discovery was presented at the European Physical Society Conference on High Energy Physics this week.