Eli5: CERN discovers 3 new ‘exotic particles’


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?

In: 29

The CERN explanation is [here](https://home.cern/news/news/physics/lhcb-discovers-three-new-exotic-particles ).

Something causes quarks to bind together into durable particles like the proton. We have little evidence for what that is and how it works. These particles might be part of the answer to those questions, but we don’t have a clear picture. It’s possible that the combination of charm quarks and charm anti-quarks in tetraquarks could explain the charm property of quarks, but there are still more questions than answers.

The significance is that the LHC is working, after a year long refurb program, and producing new data that can be accumulated into new theories.

This might be a bad analogy, but maybe you can think of the work that theoretical physicists do at places like CERN kinda like someone who knows nothing of construction trying to figure out how a house is built.

You know there are walls and floors and windows and doors, but you don’t understand how they all fit together to make this structure. So you take it apart and examine each piece, writing out how it works with and supports the pieces around it to make this whole thing.

To understand how our universe is built, physicists have to take apart the pieces that build it. Long ago, the learned people of the world thought that everything was comprised of four elements – Earth, Wind, Fire and Water. As their knowledge and understanding of physical laws increased, they saw this was not so. So the theory of +atoms was developed.

Then we realized that atoms were not the smallest thing there was. They were themselves made of smaller particles – electrons, protons and neutrons. THEN scientists found that even THESE had still smaller components that made those parts.

But we can’t actually see the parts, we can only deduce their existence and their properties by blowing them up and observing their interactions. Kinda like blowing up a house and figuring out how it’s built by how the pieces fly apart.

I don’t need to know the names and properties of every particle they find, I’m just waiting for the end result, myself.

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.

most stuff is made out of what we call atoms.

those in turn are made up of neutrons, protons and electrons.

neutrons and protons themselves are made up of quarks.

unlike the other, bigger “thingies”, quarks cant be found separately. basically they always appear in pairs or groups of three. when you try to separate them, you need to pump so much energy into them that you create new ones (that combine with the ones you have in pairs or groups of three).

well, now they’ve found that with enough power you can get groups of 4 or even 5 quarks to form an extremely shortlived kind of “cousin” of protons and neutrons.

those wont exist for more than the millionst part of a second (usually much less), so the immediate impact on our world is small.

HOWEVER this allows us to refine our models and our predictions and since there’s often “symmetries” it might lead to other discoveries.

The odds are that this will essentially “only” further our basic understanding of the universe, but there’s a fraction of a percent chance that it will also directly or indirectly lead to some crazy tech or power source (very unlikely though!)