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In reference to the findings talked about here http://online.wsj.com/articles/two-new-subatomic-particles-found-using-large-hadron-collider-scientists-say-1416409980 and other similar articles describing these, and other, subatomic particles.

What role do such newly discovered particles play in the standard model? Physics in general? What does the discovery mean for physics?

With the Higg's boson, there was an immediate problem, of sorts, or fact more accurately, which was proven when it was discovered, but with these particles there is nothing that appears to be as sensational!

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    $\begingroup$ New excited states of previously know particles. Interesting and useful but not revolutionary. $\endgroup$ – dmckee Nov 20 '14 at 14:39
  • $\begingroup$ useful in what sense? purely in that it is proof we can 'manipulate' fundamental particles or that they have a purpose? $\endgroup$ – Phizzy Dec 17 '14 at 15:47
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The new particles are baryons, and baryons are composite particles made up from three quarks. So the new particles aren't fundamental in the way that the Higgs is.

To make an analogy, suppose physicists discover a new element. That's interesting, but like all atoms it's made of electrons, neutrons and protons. So the new element is just another way of arranging more fundamental particles. Likewise, the new particles are just another way of arranging three quarks. So they are interesting, but not Earth shattering.

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The good thing about this discovery is that those particles were predicted by the standard model but never measured before. So it is, yet again, another good news for the standard model, it seems to work perfectly.

In science anyway you are more exited when you discover something that you didn't expect. In this sense the Higgs boson was unusual: we were expecting it and yet there was a big excitement. Long story short: we invested so much money and time that it became really important to discover it.

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  • $\begingroup$ And the non-existence of the Higgs would mean that the standard model was fundamentally wrong in some way. If you dont' find some particular baryon, it probably means that we've been doing qcd calculations incorrectly. And if the Higgs was much heavier than it is, it would mean that we would likely would have had to abandon supersymmetry, and therefore, also string theory. $\endgroup$ – Jerry Schirmer Nov 20 '14 at 16:16
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Quantum physics is a fascinating place, sometimes likened to a zoo, full strange noises and unexpected surprises!

If you take a tour of the subatomic zoo, you will see that there are many, many subatomic particles, not all of which are considered 'fundamental' or 'elementary' within the current theory of particle physics (known as the Standard Model).

In order to make sense of what would otherwise seem like total nonsense, physicists have engaged the services of mathematicians to seek out patterns and maintain some logic to what would otherwise appear as nothing short of mind-bogglingly paradoxical.

According to the (current) 'Standard Model' of particle physics, there are 12 fundamental particles: six of them are called 'quarks' and six of them called 'leptons'. Collectively, these are all called 'fermions' because they follow a statistical law called the 'Fermi-Dirac' distribution, in which, at any given time, no more than two such 'fermions' can exist with a certain amount of energy at a particular point in space.

In addition to the 12 fundamental fermions, there are 5 fundamental 'gauge bosons' which are the 'force carrier' particles, responsible for the four fundamental physical forces of gravity, electromagnetic, strong and weak force. Bosons 'mediate' the interaction (forces) between the particles. They therefore act as like the 'glue' which bind the other particles together.

For example, quarks can not exist on their own, but are 'bound' into composite particles (known as 'hadrons') by the strong nuclear force. This force, conveniently enough, only acts over very short distances! Composite particles made up of 3 quarks are called 'baryons'. These include the humble proton and neutron which are no longer considered 'elementary' particles. Other hadrons include 'mesons' which are made up of a quark and it's anti-quark.

There are of course many other such composite particles (hadrons) predicted by the Standard Model which have not been discovered yet, hence the significance of the Large Hadron Collider in helping scientists discover the existence of these subatomic particles and confirm (or refine) the theories. The existence of some of these 'new' hadrons may not be a complete surprise to some, as they are predicted within the Standard Model.

The major 'discovery' of the Large Hadron Collider was confirmation of the Higgs boson, which was the last elementary particle (according to the Standard Model) to be observed.

Whilst discoveries such as these, which confirm the existing theory are important, physicists are also looking for experimental data which may help confirm one theory over another, particularly in areas which are not explained within the existing model.

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  • $\begingroup$ The graviton isn't actually in the standard model and there are 8 gluons. $\endgroup$ – Chess_Player 21 Feb 10 '17 at 19:14

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