CERN discovers a new 'Tetraquark' in an experiment using the LHC, which has a long life and is expected for further research

by Morton Lin

A quark is a group of elementary particles , which are the smallest units that make up a substance. On July 29, 2021, the European Organization for Nuclear Research (CERN) reported that it discovered a new type of ' tetraquark ' consisting of four quarks in an experiment using the Large Hadron Collider (LHC). Did. The tetraquark found this time has a long life as a particle, and is expected to be a clue for further research.

Twice the charm: long-lived exotic particle discovered | CERN
https://home.cern/news/news/physics/twice-charm-long-lived-exotic-particle-discovered

New particle discovered at CERN is a long-lived double charmer
https://newatlas.com/physics/cern-new-particle-double-charm/

Up quarks , down quarks , charm quarks , strange quarks , top quarks, and bottom quarks have been found as the basic components of a substance. Multiple quarks combine by strong interaction to form hadrons such as protons and neutrons .

A normal hadron is composed of two or three quarks, but in recent years particles with more quarks have been discovered, and a hadron composed of four quarks is called a tetraquark. CERN is a high-energy physics of the conference, which was held in 2021 July 26 to 30 days EPS-HEP2021 in, reported that he has discovered a new Tetraquark named 'T cc +'.

According to CERN, a new tetraquark was discovered in an experiment using the Large Hadron Collider (LHC). The tetra quark consists of two quarks and anti-particles (anti-quarks) that have the same mass and spin but opposite positive and negative attributes such as electric charge, and the 'T cc + ' discovered this time is two charm quarks.・ It is said that it is composed of one anti-up quark and one anti-down quark.

by CERN

Multiple tetraquarks have been discovered so far, and CERN also discovered a tetraquark consisting of two charm quarks and two anti-charm quarks in 2020. However, ' T cc + ' has two charm quarks with the third largest mass among the quarks, while the antiquarks that combine are the down quark with the fifth smallest mass and the up quark with the sixth smallest mass, and are particles. It is characteristic that the masses of quarks and antiquarks are not balanced as a whole.

Because the mass of charm quarks is much larger than that of down quarks and up quarks, researchers call particles without anti-charm quarks that balance the mass of charm quarks 'open charms'. In the case of 'T cc + ', the mass of two charm quarks is not balanced with the antiquark, so it is said to be 'double open charm'.

In addition to being a double open charm, 'T cc + ' has the longest lifespan of any special hadron (exotic hadron) found so far. Tetraquark, which consists of two heavy quarks and two light quarks, is said to be divided into intermediates consisting of 'one heavy quark and one light quark' and collapse. CERN explains that a tetraquark consisting of 'one anti-up quark and one anti-down quark' is less likely to disintegrate than other particles due to its mass.

According to CERN, the discovery of 'T cc + ' has the potential for research such as searching for longer-lived tetraquarks by replacing two charm quarks with 'two bottom quarks' and measuring the quantum number of particles with high accuracy. It is said that it will open.