Atom Smasher

I was watching the morning news last week when a pair of elaborately-coiffed newsreaders (one hesitates to call them "journalists") had a bit of a yuk-yuk over those dumbassed coneheaded scientists who had already broken their new toy, the Large Hadron Collider at CERN in Switzerland. They thought this was quite funny, drawing all sorts of conclusions about how highbrow scientists can't be trusted with expensive equipment, unlike (say) elaborately-coiffed newsreaders. Excuse me, dear newsreader but do you even know what a goddamned hadron is? This streak of American anti-intellectualism kind of irritates me. No, it doesn't "kind of" irritate me; it just flat-out irritates me, and I simply can't see why people would be proud of their selective ignorance.

But what, really, is the Large Hadron Collider all about? What does it do? At its heart, it is a giant circle some 27 kilometers in diameter. It passes a beam of protons around this circle, accelerating them to the highest speeds possible, before steering them into head-on collisions with fixed targets or (even more fun) a beam of anti-protons circling the opposite direction. Let's not worry about that latter business too much for now.

What's a hadron? Physicsts divide the dizzying array of subatomic particles into several general categories based on various physical characteristics. In this case, we're using weight. Light particles (like electrons) are called leptons, which is Greek (I think) for "light ones". Medium-weight particles (like pions) are called mesons, which is Greek (I think) for "medium-weight ones." Heavy particles, like protons and neutrons, are called hadrons, which is Greek (I think) for "heavy ones." So that's all a hadron is, a heavy particle with a rest mass somewhere in the ballpark of the proton and on up from there (some hadrons get really heavy indeed).

(Update: I was lying in bed last night after my dosing with tonic water, spluttering and shuddering, when it struck me that I'd confused hadron with baryon. In the preceeding discussion, this business of light, medium and heavy particles, what I called hadrons are in fact baryons, and the distinction has really nothing at all to do with the LHC. Nay. Hadrons are a class of particles that are bound together by the strong nuclear force, chiefly protons and neutrons.)

Why are we colliding hadrons? What's in it for us? What, fundamentally, is the point of all this? One point would be proving or disproving the validity of the "Standard Model" of quantum mechanics. Fundamental to this model is the existence of the so-called "Higgs field", along with its associated "Higgs particle". These are required to exist by the Standard Model because they enforce symmetry breakages at specific energies, but nobody's ever actually seen a Higgs particle. Proving or disproving the existence of the Higgs particle would have major consequences for particle physics and cosmogony, to name just two areas.

The "Standard Model" of quantum mechanics also predicts the theoretical existence of other particles, most of them fairly exotic, like gluons and quarks. Proving that these particles really exist (or proving that they don't really exist) would have a major impact on quantum physics (if we can't prove quarks exist, well then, we've got a lot of work to do).

So how would we prove that quarks, gluons, Higgs particles and other exotic particles exist? The basic problem is that they can exist only in very high energy situations, such as the first few milliseconds after the Big Bang or in the heart of a thermonuclear weapon, neither of which are entirely feasible experimental apparati - there's only been one Big Bang that we know of, and one imagines that a grant proposal that includes the line "...then we detonate the hydrogen bomb..." would likely not get past the National Science Foundation safety people.

So that's the problem. To detect these exotic particles, we first have to create them, and to create them, we need to jam an awful lot of energy into a fairly small area. In particle physics, the easiest way to produce high energies is to slam atomic nuclei or subatomic particles at high speed into targets of various sorts (some of them as ordinary as chunks of aluminum). We remember from our high school physics that the kinetic energy of a moving object is a product of the mass of the moving object times the square of the speed - KE = 1/2 MV^2. The easiest way to increase the energy is to increase the speed of the collision, but if you're already pushing particles as fast as you can, the only way to increase energy is to increase the mass of the particles.

Think of it this way. You're standing at a table covered with ping pong balls and steelies, and ten feet away is a pane of glass that you'd like to break. So you throw a ping pong ball at the glass, and it bounces off. So you throw a ping ping ball harder, and it still bounces off. Eventually you're throwing ping pong balls as hard as you can, hard enough to dislocate your shoulder and produce that funny sensation of recoil up your neck and into your brain. And still the window doesn't break. Conclusion: we've gotten all the speed we can out of the accelerator (your arm) so to increase the energy we're going to have to increase the mass of the particle. Grab a steelie and throw it, and it shatters the window.

That's exactly what the LHC hopes to do. It hopes to move the heaviest practical particles, protons, at the highest practical speed, just shy of the speed of light, and by so doing pack enough energy into collisions to crease a few of these Higgs particles and gluons and quarks and whatnot that are predicted to exist at high energies. It is different from other particle accelerators simply because it is larger and operates at higher energies - it's the Ferrari of particle accelerators, one could say.

Will it work? It'll probably successfully liberate quarks and gluons. Indeed, they've already been claimed to have been seen in other particle accelerators, but in such densely packed messes that they've been hard to study. The LHC might produce them in an environment that is easier to work with. Will it find the Higgs particle? I hope so, but I'm not entirely sanguine. For one thing, the theoretical predictions of the mass of the Higgs particle are awfully one-sided. They say "It has to be at least this heavy, but it may be a lot heavier." Meaning, if we don't see it with the LHC, it might because there's no such thing as the Higgs particle, or maybe because the Higgs particle is just a hair too heavy for the LHC to produce. Things like this drive me crazy.

The End Of The World Angle

People have been worrying a lot lately about whether the LHC will create "quantum black holes" that will eventually cause the destruction of the Earth. The theory is that the quantum black hole, once generated, will slowly settle to the center of the Earth, where it will slowly consume the crystalline and liquid iron at the core and become a not-so-quantum black hole, whereupon it will either (choose your poison) consume the Earth entirely, or blow the Earth to smithereens with high-energy gamma rays.

It's possible, I suppose, but I think it's unlikely. My reasoning goes like this. The Earth is constantly bombarded by cosmic rays, which are basically nothing more than protons and other charged particles from deep space. Some of these particles are most impressively energetic, to coin a phrase. One of them, referred to as the "Oh-My-God Particle", had roughly the energy of a baseball thrown by a major league pitcher. In fact, some of these particles pose problems for Special Relativity in that they seem to exceed the GZK Limit, a sort of "speed limit" imposed by interactions between the particles and the photons of the background radiation; above a certain velocity they would interact and bleed off energy in the form of pions. But we occasionally detect particles well above the GZK Limit, which seems to hint that either Special Relatively is wrong or is inconsistent at large scales (leading to formulations such as "Doubly-Special Relativity").

My point has nothing to do with GZK limits. It has to do with the idea that very high energy cosmic rays fill space, and there are uglier things out there too, gamma rays and x-rays, and all of this shit (no other word will do) flies around and collides and never seems to produce quantum black holes, at least not that we've ever seen. Not even supernovae seem to produce the beasts. If the universe itself seems disinclined to produce quantum black holes with all of the energies and particles at its disposal, I can't really see the LHC making any either. If the LHC were closer to the Planck energy I might be more worried, but it's nowhere near that level of performance.