# Batting averages of the Large Hadron Collider

As I understand it, the Large Hadron Collider's function is to throw particles into each other while avoiding hitting the nucleus?

If quantum mechanics dictate the position of a particle can only ever be an educated guess how accurate or reliable is the collider's standard results for a successful observation? Does it miss more than it hits?

What happens if the nuclei collide, would their impact result in a nasty reaction that would destroy the collider at the least?

I can go on, has it ever done so and what was the effect?

-
By the way, QM doesn't really say the position of a particle can only be an educated guess, it says it is determined by a probability distribution. But that's a separate issue ;-) – David Z Jun 30 '12 at 1:19

 As I understand it, the Large Hadron Collider's function is to throw particles into
each other while avoiding hitting the nucleus?


No. In the nuclei are the quarks and trust me, we want to beat the crap out of them (the quarks) with as many direct hits as possible.

 If quantum mechanics dictate the position of a particle can only ever be an educated
guess how accurate or reliable is the collider's standard results for a successful
observation? Does it miss more than it hits?


As far as the uncertainty principal goes, its doesn't forbid you from creating states that still have very small uncertainty in space and momentum. In the case of the LHC the wavefunction of the protons is still fairly localized to a small peak that they send around the collider, outside of which there is a negligibly small chance of detecting the proton. So just because the proton is quantum mechanical doesn't mean there is an equal chance of detecting it anywhere in Geneva.

Furthermore, what little uncertainty in the proton wave-packets there is, it isn't much of an issue as far as I can tell. Most of the time something is making contact when the beams cross. The real question is, how often does something interesting happen? It turns out not often - they don't bother recording something like >%99 of the data simply because nothing interesting happened. That is, an automated quick check of the data is performed to see if something triggered an interesting channel, if it doesn't they dump that data, and if something (possibly) interesting happens they store the data and look at in detail later all together.

 What happens if the nuclei collide, would their impact result in a nasty reaction that
would destroy the collider at the least?


The nuclei collide all the time and the collider is still here. More importantly there is much higher energy processes happening all the time in the universe for a long time and we are still here.

-

Most of the time, the LHC is focusing opposite traveling bunches of protons, in a vacuum so as to avoid undesired collisions with nuclei, together at the various detector locations. No nucleus is involved unless the LHC is colliding heavy ions in which case, the ion nuclei collide and produce amazing images but no damage to the collider.

According to one LHC FAQ:

When the bunches cross, there will be only about 20 collisions among 200 billion particles. However, bunches will cross about 30 million times per second, so the LHC will generate up to 600 million collisions per second.

-
Which of course results in a batting average on order of 000.000001...which is actually very good by collider standards. – dmckee Jun 29 '12 at 21:04
It might be good to correct the OPs misunderstanding that the goal is to avoid colliding nuclei. In colliders that use heavy ions, that is exactly the goal; in colliders that don't use heavy ions, it's not hard to avoid the nuclei because there aren't any. – Colin K Jun 29 '12 at 21:15
Indeed! Will clarify. – Alfred Centauri Jun 29 '12 at 21:27