# Do the particles made in a collider exist outside the collider?

Below is the transcript of a section from Demystifying the Higgs Boson with Leonard Susskind. Around 1:02:23 Susskind says that

the heaviest of the fermions is called the top quark. Top quark is thousands of times heavier than the electron many many times heavier, and higgs preferentially will decay into top quarks. (higgs cannot decay to quarks because they are too heavy. so you take two quarks and align them to produce higgs! ... Go into the laboratory and take two top quarks, collide them together and make a higgs. The problem is that it is not so easy to find top quarks in nature... why not? they decay very rapidly to the other quarks. They are not sitting around. You cannot put them in the accelerator and accelerate them... they disappear in a tiny fraction of a second. There are no top quarks sitting around. Not even buried in protons and so forth. You have to make top quarks somehow in the collision...

My question is, are the particles that reveal themselves in a collider exist outside the collider, that is, outside the strong electric and magnetic fields that make them?

What I am trying to understand, if Higgs or quarks are "fundamental" and "elementary" particles, are there any experiments showing that they exist outside the magnetic and electric field that create them?

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– jinawee Nov 10 '13 at 23:51

This answer is not to the topical question but to the OP's comment to an answer:

Sorry for the ignorance, but, if so, are protons and neutrons observed outside electric and magnetic fields?

How does one get "outside" of electric and magnetic fields? Classically, a single charged particle has an electric field that extends over all space.

Further, quantum field theory wise, the quantum fields are fundamental - there is no getting "outside".

I think you should closely examine the presumptions you hold, to even ask this question, and do some further reading and thinking.

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"How does one get "outside" of electric and magnetic fields?" I would say that when you turn off electricity and magnetism you do not have electricity and magnetism. Is this not correct? – Zeynel Nov 11 '13 at 2:15
@Zeynel, how does one "turn off" electricity and magnetism? – Alfred Centauri Nov 11 '13 at 2:18
"how does one "turn off" electricity and magnetism?" I would say when the LHC is not powered and there is no beam, it is "turned off". Is this not so? – Zeynel Nov 11 '13 at 2:38
Yes, I think that phenomena that LHC was built to observe can only happen when LHC magnets are turned on. When electricity and magnets are turned off (if you want I can supply the link for LHC off state) then these phenomena that happen in LHC do not happen. If they did, there would be no need to build LHC. Are you disputing this fact? – Zeynel Nov 12 '13 at 23:49
@AlfredCentauri I think Zeynel is using "electric and magnetic fields" to mean "electric and magnetic fields of a very high intensity, as found inside a collider." In that case it makes perfect sense to talk about turning them off. – Nathaniel Nov 13 '13 at 8:58

There's no direct way to measure the Higgs particle directly. The way you use is basically measuring the particles, to which it decays. Take a look at the following Branching Ratio plot for the Higgs particle:

So check for example the decay of $\gamma \gamma$. What you do is that you look for somethings that you can measure on that curve, for example those $\gamma \gamma$ photons, and you measure the energy and momentum of those photons, and they have to satisfy the branching ratio curves that you see.

Yes, those particles (or fields basically) exist outside the collider, but we have no way at all to measure them, and actually we can't measure them even inside the collider some times, and we use some very sophisticated tricks to make this measurement possible.

One more thing I would like to mention is the idea of something that "exists"... actually if we talk in terms of quantum mechanics and quantum field theory, everything exists all the time, because you have quantum states which are superposition of all possibilities, but when you measure them, one of the possibilities show up. So, some particles exists with a very low probability, and that's why it's very hard to find them when doing a measurement, and some particles are almost all the time there. (Yes, it's crazy, but it's true).

Hope this helps.

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It depends on what particle you're talking about.

Up and down quarks are everywhere, since they constitute protons and neutrons.

The problem with the Higgs and the top quark is that they have a big mass, so you need high energies to create them and you won't generally find them, except in cosmic rays or other high energy sources.

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Sorry for the ignorance, but, if so, are protons and neutrons observed outside electric and magnetic fields? – Zeynel Nov 10 '13 at 23:33
@Zeynel Of course, you're a bunch of protons and neutrons. For example, the proton was discovered in 1918 by Rutherford. – jinawee Nov 10 '13 at 23:38
A quick search, e.g., this page, suite101.com/a/rutherford-and-the-atomic-nucleus-a45825 appears to say that protons were discovered in a magnetic field: "...which Rutherford determined by exposing the resulting hydrogen to magnetic fields..." If so my question is still valid. Thanks. – Zeynel Nov 10 '13 at 23:55
@Zeynel Well, particles will exist even if you don't measure them. And what Rutherford did was totally different from particle colliders, the energies are much lower and they don't create any particles. – jinawee Nov 11 '13 at 0:12

The Higgs boson and all the flavours of quark are indeed physical and they do "exist" physically. It is indeed possible, in principle, to detect them directly, both within the collision environment, at the detector, or outside it.

The problem, however, is that their existence is temporally very brief. Higgs bosons do pop into existence in the LHC, but unfortunately their lifetime is very brief. Therefore, they decay before they've had any chance to get out or even make it to the detector. This means that all we can do is measure their decay products. However, this does not mean that they did not exist in the first place.

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Ok, can you sketch an experiment that, "in principle", can detect a "fundamental" particle without using electricity or magnetism? Otherwise, you phrased your answer as an opinion without physical basis. – Zeynel Nov 11 '13 at 0:41
There is no opinion anywhere. This is all standard physics. On the other hand, it is impossible to 'design an experiment without using electricity or magnetism' to do... anything. All detections of particles are via electromagnetism, as are all other experiments in physics. We can detect and observe the gravitational and strong and weak nuclear forces, but our apparatus will always depend on electromagnetism, if only to stay together as a coherent object. – Emilio Pisanty Nov 11 '13 at 1:25
As for the sketch, it's easy: if a Higgs or a quark ever made it to the detector, it would be visible in the same way as all other particles produced in the collision. – Emilio Pisanty Nov 11 '13 at 1:26
"All detections of particles are via electromagnetism, as are all other experiments in physics." Maybe I am not reading you correctly, but this sentence appears to say that there are no experiments where these fundamental particles are observed outside magnetic and electric fields. If so, my question is still valid: How do we know these particles are not artifacts of electricity and magnetism? – Zeynel Nov 11 '13 at 1:41
You are reading me correctly. There are no experiments where detection of any particle takes place by means other than electricity and magnetism. For further information, please see Alfred Centauri's answer. Have a good day. – Emilio Pisanty Nov 11 '13 at 1:45

This answer is also to a comment by the OP to the answer of @EmilioPisanty. The OP insists

If so, my question is still valid: How do we know these particles are not artifacts of electricity and magnetism?

Physics at the present time has modeled all of nature quite successfully, i.e. ordering and prediction almost all data in particle physics, called the Standard Model .

In this model, the SU(3)xSU(2)xU(1) symmetries of the Lagrangian actually create as artifacts of the symmetry all elementary particles in the table and all the dynamically produced composites from these.

There is no way out of electromagnetism. The fact that you are reading this depends on innumerable electromagnetic interactions of photons with your eye and brain (virtual photons in the chemical messaging). In everyday life all data coming into our brain is electromagnetic and everything we can construct and use to detect anything depends on electromagnetism.

U(1) is the symmetry of electromagnetism in these groups and yes, everything is an artifact of the combination of forces , weak strong and electromagnetic. This has been the most economical way of describing the experimental data, and encapsullating them in one mathematical model.

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Physics at the present time has modeled all of nature quite successfully, i.e. ordering and prediction almost all data in particle physics, called the Standard Model. I am confused about the sweeping and absolute generalization in this sentence. Is it really true that "physics has modeled all of nature…"? This seems to me hyperbole that is not justified by observations. "All nature" includes, for instance, biology. How much of biology can physicists model using the Standard Model Lagrangian? – Zeynel Nov 16 '13 at 2:02
"All of nature" includes, genetics, how much of the Standard Model Lagrangian models genetics? The way I see it, Standard Model Lagrangian is limited to modeling some specialized events happening in high energy colliders. I cannot agree with your implicit reasoning that "everything is made of particles, we model collisions of particles, therefore, we conclude that we modeled 'all of nature'" – Zeynel Nov 16 '13 at 2:03
"All of nature" in the sense of the foundation of all of nature. The model physicists accept and the one most scientists in other disciplines accept, as far as measuring physical properties of the type length, time, energy, mass and similar, is that the underlying nature is a quantum mechanical framework working on "particles" which carry the quantum mechanical duality of particle/wave. Riding on this is the meta level of atoms molecules and all of solid state and biological models, still displaying quantum mechanical quantities but using the lower level as an alphabet (example). – anna v Nov 16 '13 at 4:46
When dimensions and times and energies become large enough so that the h_bar of the Heisenberg Uncertainty Principle is to all intents and purposes of measurement zero, the classical domain is reached as a further meta level using the underlying atomic level as an alphabet ( a new language written on an underlying alphabet). In this sense yes, the Standard Model explains nature, in the way that foundations hold up the whole building. Different foundations might have done the same job, but the experimental fact is that these are our foundations. – anna v Nov 16 '13 at 4:50