Particle accelerators and colliders

Factual Questions
1

When you slam protons and neutrons together in particle accelerators you see in bubble chambers that they “explode” into all sorts of smaller particles. My understanding is there are currently something like 80 different particles smaller than protons and neutrons that have been observed.

Question 1:
I also understand that most of these particles only exist for brief moments…and then…what? Do they recombine to form protons and neutrons or do they disintegrate into photons or what? Anyone know?

Question 2:
Is it reasonable to say that if you smash protons, neutrons, and electrons hard enough they will ultimately reduce to pure energy? Photons? Is this implied by the equation E=mc^2?

As always I appreciate web site links and book recommendations for easy to read info.

2

This is an extremely difficult question to answer in a short space (like less than a couple hundred page?).

But first, nuetrons are generally not accelerated. Accelerators use electromagnetic fields to propel the particles. Neutrons have no electric charge and therefore don’t work as projectiles in these devices.

I would answer first by pointing you to some pretty good books.

First book, “QED: The Strange Theory of Light and Matter” by Richard Feynman. Probably hard to find a much clearer explanation of Quantum Electro Dynamics and you will get introduced to wit of Mr. Feynman. This will give you the basics of our understanding of quantum behavior and then into understanding the atom to the level of why the parts of atoms that we interact with (electrons) behave the way the do.

Next book, find a good book on QCD (Quantum Chromo Dynamics), perhaps chronos can help you find this one. This will explain that the principals you learned in the first book still apply at the nuclear level and start spelling it out for you. I thought Richard Feynman did a book on QCD, but I can’t find it… maybe I am missing it. The QED will keep ya busy for a while though.

The short answer to your Q1: It varies
Q2: No, but you can use the kenetic energy of a collision to make particle anti-particle pair from scratch. When these come together they will/can vanish into “pure energy”. E=mc^2 governs this. In the end, your starting pieces will still exist (some provisios apply).

Fenyman uses 158 pages to explain QED, and you need more than that to really get to heart of what you are asking. I can’t think of way to sum it up here in a couple of paragraphs.

3

Actually, you usually get particles heavier than the original protons (the extra mass comes from the kinetic energy of the original particles). The only known particles lighter than the proton are:

Two of the three species of charged leptons (electron and muon) and their antiparticles
Three corresponding species of neutrinos, and (maybe) their antiparticles
A total of 16 of the mesons, counting particles and antiparticles (some of these are their own antiparticle)
Three of the six quarks, and their antiparticles, though these can’t be isolated
Three of the vector bosons (photon, gluon, graviton), all of which are massless and their own antiparticle (of these, only the photon has been directly detected)
For a total of 37 known particles lighter than the proton. Now, there’s also an unlimited number of particles heavier than the proton. Any object can, in principle, be considered as a “particle”, albeit a very complicated one, but things larger than atoms or so usually aren’t.

Most of these are unstable. The only things that are stable are the electron, the three neutrinos (a bit debateable), the photon, gluon, and graviton, the proton (maybe not, but it lasts next best thing to forever), and some atoms made up of protons, neutrons, and electrons (the neutrons themselves aren’t stable, but the atoms can be). They all decay into something, ultimately getting down to those handful of stable particles, but what the end results are, and what path it takes to get there, depend on the original particle.

Some decays are impossible, being forbidden by various conservation laws: For instance, if you start off with something charged, you have to end up with something charged, and if you start off with baryons (things like protons and neutrons), you have to end up with baryons. Some particles, on the other hand, can decay to nothing but light: The [symbol]p[/symbol][sup]0[/sup], for instance, typically decays to two photons.