# Why did it take a long time to discover top quark?

In high school physics, I learned that it took a long time before the top quark was discovered. One of the reasons that was given in my book was that the top quark has a large mass, much larger than the other 5 quarks, and there just wasn't a powerful enough particle accelerator to produce large energies.

My doubts:

1. In such an experiment, do high speed particles just collide and energy is just given off that can be converted to mass? Is this how quarks are produced?

2. As far as I can understand, in a particle collision, large energy is produced and this is converted to mass i.e. a top quark in this case. However, I also learned that individual quarks cannot exist and hadrons form... so how did scientists get an individual quark?

3. If the top quark was formed from energy, it must mean that there was a "pair production" and an anti-top quark is also supposed to be produced. So, does the collision have to produce energy that is equivalent to the mass of two top quarks?

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Re your question 1, have a look at my answer to Conversion of mass and energy. You might also want to look at What keeps mass from turning into energy?, which is related. These give a basic desciption of how the energy of motion can turn into particles of matter like top quarks.

Re questions 2 and 3: the discovery of the top quark was made at the Tevatron in 1995. Top-antitop pairs were created and identified by their decay products. There's a nice article on this here.

You are correct that twice the energy of a top quark is required, because you have to create both a top and antitop. The collision energy in the Tevatron was 1.8TeV. However the Tevatron was colliding protons and antiprotons, and the actual collisions are between the quarks and antiquarks that make up the proton. Any particular quark has only a fraction of the total energy of the proton, so the collision energy has to be well above the approx 350GeV needed to create a top-antitop pair. That's why such a high energy collider was required.

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