Can someone explain this in laymens terms? I don’t know what Pentaquarks or tetraquarks or whatever else this stuff mean. And what does this change about what we know about physics or sub atomic particles etc?
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Ordinary matter is made up of atoms, which consist of a cloud of electrons and a central nucleus, which is made up of protons and neutrons. Protons and neutrons are themselves made up of quarks, and there is a force called the strong nuclear force which is the main thing responsible for holding both nuclei and protons/neutrons together.
The strong nuclear force is kind of like a much more complicated version of electromagnetism. For example, the key property that determines how particles interact electromagnetically is their “charge”, which can be positive or negative. But the main property for the strong force is something which has been dubbed “colour charge” and which comes in three different flavours, known as red, green and blue (these are just arbitrary names – it has nothing to do with actual colour). Antiquarks are instead antired, antigreen or antiblue. There is a phenomenon called “colour confinement” which ensures that quarks only exist in arrangements in which the colour charges balance out – red+green+blue balance out, as do red+antired, antired+antigreen+antiblue, etc. For example, in a proton you will always have a red quark, a green quark and a blue quark (though they constantly switch colours with each other). You don’t just get free quarks floating around by themselves. But there are two other possible arrangements of quarks which have been known about for a long time. In addition to baryons (particles made of three quarks) you can get antibaryons, which are made of three antiquarks, and you can get mesons, which are made up of one quark and one antiquark. Mesons are unstable, but they play a very important role in some physical processes.
There has long been speculation about other, “exotic” arrangements of quarks in which the colour charges would balance out. The simplest are the tetraquark, consisting of two quarks and two antiquarks, and the pentaquark, consisting of four quarks and an antiquark. In recent years a number of experiments have started to find evidence of tetraquarks and pentaquarks, but the LHCb experiment has placed these discoveries on a firm footing and has now identified several specific tetraquarks and pentaquarks with a high degree of certainty. These particles are unstable and only exist for a very short length of time, and it’s not clear how important they are. But the strong force is still quite poorly understood (due to being so hecking complicated), so I’m sure these results will be useful to people trying to understand it better.
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