Russian scientists participating in the LHCb collaboration at the Large Hadron Collider have announced the discovery of a new particle — the exotic tetraquark Tcс+. This is a new form of matter, a press release published on the CERN website said.
Tcc+ tetraquark is the only particle known to science that consists of four quarks, two of which are charmed (c-quarks) with no presence of charmed antiquarks.
The charm stands for a flavour quantum number that characterizes the type of the quark (there are six different "types" of quarks known in total). At the same time, the lifetime of a new tetraquark is approximately 10-500 times longer than that of particles with a similar mass, which makes Tcc + tetraquark the longest-lived record holder.
It was originally believed that hadrons (compound particles) could only consist either of three quarks, like protons and neutrons, or of one quark and one antiquark. However, more than 50 years ago, physicists suggested that there were hadrons, consisting of four (tetraquarks) or five quarks (pentaquarks).
The existence of four pentaquarks and 20 tetraquarks has been experimentally proven.
The Tcc+ tetraquark consists of two heavy charmed quarks (denoted as cc), and two antiquarks with flavors u (up) and d (down). Previously known tetraquarks had hidden charm, that is, they contained an enchanted quark and an enchanted antiquark.
According to scientists, it is the presence of two heavy quarks that makes the particle relatively stable and long-lived. If instead of c-quarks there were b-quarks (beauty quarks) in it, then the particle lifetime would become even longer and amount to 10 to the minus 13th power of a second.