Wednesday, April 08, 2009

Know Your Reference (Quark Matter 2009)

So much for those dispatches: I could barely figure out where I wanted to be at any given time, much less come up with reasonable summaries of what I had just seen. Conferences are like that. Anyway, I do have a few photos, but just a few. Above you can see Bill Zajc of Columbia University telling us a few things to keep us focussed, two of them not about heavy ions at all, but about the "control measurements" we do with smaller systems that we assume are "references".

Now that I'm home, it's interesting to reflect on how little attention we've questioned our reference systems as such. Generally, the less we worry about them, the better we feel, since they then remain "someone else's" problem (i.e. that of our particle physicist friends). However, the more I hang out in this neck of the scientific woods, the less I believe that nominally "simple" systems are that simple (even protons are made of many quarks and gluons), or are even that different than the bigger systems we create with huge (ok, still subatomic) nuclei. While it can be a little confusing, I find these ambiguities the most compelling aspects of this business.

I'll get to this in the next few posts. In the meantime, if you want to see the official summaries, check out the four rapporteur talks here.

1 comment:

Mike Lisa said...

''Generally, the less we worry about [our reference systems], the better we feel, since they then remain "someone else's" problem''

Peter, excellent point. Bill's comments are generic to science in general, and heavy ion physics tends to ignore them. I think it is a legacy from our evolution from lower energies, where it was pretty clear that *nuclei* had physics well beyond hadronic physics. We carried that assumption to ultrarelativistic energies-- where *nuclear* effects in the traditional sense are irrelevant-- and forgot where the assumption came from. New students-- the ones who grew up in the ultrarelativistic era-- are raised with the built-in view that heavy ion collisions are "obviously" very different than hadronic ones.