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6rant6's avatar

What does CERN's luminosity record mean?

Asked by 6rant6 (13705points) April 27th, 2011

CERN announced that they set the record for the highest luminosity ever in their particle beam. It’s 4.67×10^32 / Cm^2 per this article

It sounds very impressive to have all those zeroes, but I don’t quite understand. It seems like there is a unit missing – “Gleekos per Cm^2,” or something. If so, what is it? How does this compare to, say, daylight, or a 60 watt bulb at a meter?

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6 Answers

dabbler's avatar

I agree there’s some unit missing… This article link about a Japanese collider comes close to defining it as the number of collisions on a surface per second. It would have direct correlation to beam density and the more collisions in a target area the more statistically likely it is that something interesting will happen !

FireMadeFlesh's avatar

From your link – “The new record measured a level of luminosity of 467,000 billion billion billion—467 followed by 30 zeros—per square centimetre per second”.

The units in question are collisions/cm^2/sec.

6rant6's avatar

Still not enough information.

So there’s apparently a very narrow beam that if it were as wide as1 cm^2 would result in 4.67×10^32 PHOTON collisions with anything placed in it’s path? How does that compare with something I am familiar with, like sunshine?

FireMadeFlesh's avatar

I must apologise, my previous answer was grossly incorrect.

Luminosity, in this sense, appears to be a measure of beam intensity. “Luminosity gives a measure of how many collisions are happening in a particle accelerator: the higher the luminosity, the more particles are likely to collide.” (Source). That means, as far as I can tell, that the units given are correct. A beam of X luminosity is equivalent to a beam in which X number of particles pass through 1cm^2/sec. This serves to increase the probability of collisions, due to a greater density of particles.

dabbler's avatar

@FireMadeFlesh that sounds like a correct definition but I’d still agree with @6rant6 that it could make more sense to put particles/cm2*sec or collisions/cm2*sec. Or are those ‘units’ close but not really correct either?

FireMadeFlesh's avatar

@dabbler This is really going beyond my knowledge now, and I’m sure they have a good reason for expressing it in that way. Maybe there is a weighting factor applied depending on the types of particles involved as well, since a proton beam wouldn’t really be comparable to a neutron beam or an electron beam etc. Also on that scale, each particle appears as a wave function, so you cannot say it is in a particular location. Therefore you cannot say X number of particles are within a certain space when the given space is so small, because no particle is definitely within that space.

I’ll do some more reading and see if I can find a better answer. This question is really bending my mind!

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