Roughly - and a warning to experts: a bit of what I’m going to say now is naive and actually misleading, and I’ll correct it later - what happens is the same process shown in Figure 1, but on steroids. What happens when a high-energy quark is kicked out of a proton? For instance, suppose a speeding electron plows into a proton and hits a quark really hard, giving it a motion energy much larger than the mass-energy of the entire proton?!
#What does a quark look like free#
Thus your attempt to free the quark from its prison would inevitably fail, and the energy that you exerted to do so would instead be converted into the mass-energy of a second hadron. 1: If you tried to pull a quark out of a proton (using a magical pair of tweezers), you would discover the proton would first distort and then break into two hadrons (perhaps a proton and a neutral pion). Electric charge is conserved too, so you either end up with a neutral pion and a proton, or a positively-charged pion and a neutron.įig. (In the breaking, a quark and anti-quark pair form in a particular way- energy in the form of the band’s tension is converted into mass-energy of the quark and anti-quark, along with some motion-energy for some additional gluons.) Energy is conserved: you started with the mass-energy of the proton, you added some energy in stretching the proton, and you end up with the mass-energy of two hadrons (and nothing stretching).
#What does a quark look like plus#
What happens when it breaks is that instead of one hadron (the proton) you now have two: a proton or neutron, plus (typically) a pion. Once the energy stored in this elastic band gets large enough, nature would prefer to break the band in two rather than let you keep pulling on it. Except that this rubber band, before you pulled it too far, would always break. It would be almost like pulling on a rubber band - an elastic string. And that means that if you could try, for instance, to pull a quark out of a proton, as in Figure 1, you would find that it would not get easier as you tried to pull the quark further and further out. Instead, the force, generated by the gluon field, becomes a constant. That’s not an accident the size of a proton is actually set by this effect. What happens with the strong nuclear force is that although it too grows at short distances and shrinks at long distances (though a tiny bit slower than electric forces do, which is important in the story of the strong interactions) it stops shrinking at distances of about a millionth of a billionth of a meter (a meter is about three feet), which is just about the radius of a proton, or 100,000 times smaller than the radius of an atom. You see this yourself when you rub a balloon, making it charged with “static electricity” as we call it colloquially if you bring the balloon close to your head your hair will stand on end as it is attracted to the balloon, but the effect drops off quickly as you move the balloon away. The same is true of the electrical force between two charged objects, which also falls off like the square of the distance. Most forces between two particles become weaker with distance for example, the gravitational force between two planets falls off as the inverse of the square of the distance between them. This feature, which makes quarks behave so differently from charged leptons, neutrinos, photons and the like, is a consequence of the fact that quarks and gluons are affected by the strong nuclear force, while the other known particles are not. In this article I’ll give you a rough idea of how and why a jet is created from a high-energy quark, anti-quark or gluon. Instead, a high-energy quark (or gluon or anti-quark) is transformed into a spray of hadrons. It is a fascinating aspect of the physics of our world that when one of these particles is kicked out of the hadron that contains it, flying out with high motion-energy, it is never observed macroscopically. Quarks, gluons and anti-quarks are the constituents of protons, neutrons and (by definition) other hadrons.
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