![]() When quarks were first discovered, scientists realised that several combinations should be possible in theory. Worse still, we can’t even calculate which combinations of quarks would be viable in nature and which would not. We therefore cannot (yet) prove theoretically that quarks can’t exist on their own. An unpleasant feature of the theory of the strong force is that calculations of what would be a simple process in electromagnetism can end up being impossibly complicated. This has been shown repeatedly by experiments – we have never seen a lone quark. This may sound weird but according to quantum mechanics, which rules the universe on the smallest of scales, particles can pop out of empty space. You end up with a proton and a brand new “meson”, a particle made of a quark and an antiquark. If you pull a quark out of a proton, the force will eventually be strong enough to create a quark-antiquark pair, with the newly created quark going into the proton. To complicate matters further, all the particles in the standard model have antiparticles which are nearly identical to themselves but with the opposite charge (or other quantum property). Unless, of course, you smash them open at incredible speeds, as we are doing at Cern. As a result, quarks are forever locked up inside particles called hadrons – particles made of two or more quarks – which includes protons and neutrons. While the electromagnetic force gets weaker as you pull two charged particles apart, the strong force actually gets stronger as you pull two quarks apart. However, the way gluons interact with quarks makes the strong force behave very differently from electromagnetism. You can think of gluons as analogues of the more familiar photon, the particle of light and carrier of the electromagnetic force. It describes how quarks interact through the strong force by exchanging particles called gluons. “ quantum chromodynamics”, is on very solid footing. If we switched the strong force off for a second, all matter would immediately disintegrate into a soup of loose quarks – a state that existed for a fleeting instant at the beginning of the universe.ĭon’t get us wrong: the theory of the strong interaction, pretentiously called The nucleus is made up of protons and neutrons, which are in turn each composed of three tiny particles called quarks (there are six different kinds of quarks: up, down, charm, strange, top and bottom). One of its most troublesome features is its description of the strong force which holds the atomic nucleus together. That said, the theory is still far from being fully understood. And the LHC has delivered the goods – it enabled scientists to discover the Higgs boson, the last missing piece of the model. The LHC’s goal is to explore the structure of matter at the shortest distances and highest energies ever probed in the lab – testing our current best theory of nature: the Standard Model of Particle Physics. Excitingly, while some of these new particles were expected based on our established theories, some were altogether more surprising. This means that the LHC has now found a total of 59 new particles, in addition to the Nobel prize-winning Higgs boson, since it started colliding protons – particles that make up the atomic nucleus along with neutrons – in 2009. Of four brand new particles at the Large Hadron Collider (LHC) in Geneva.
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