Comments on: Time Machine Possible in New Particle Accelerator http://www.nuclearblog.org/2008/02/19/time-machine-possible-in-new-particle-accelerator/ Fri, 05 Sep 2008 16:45:07 +0000 http://wordpress.org/?v=2.3.2 By: Richard Bindel http://www.nuclearblog.org/2008/02/19/time-machine-possible-in-new-particle-accelerator/#comment-78 Richard Bindel Fri, 20 Jun 2008 20:38:28 +0000 http://www.nuclearblog.org/2008/02/19/time-machine-possible-in-new-particle-accelerator/#comment-78 On a different note, this blog seems a little Berkeley-centric at the moment, but here at U. of Maryland, me and my east-coast posse are all about Professor Mather and *his* Nobel Prize! On a different note, this blog seems a little Berkeley-centric at the moment, but here at U. of Maryland, me and my east-coast posse are all about Professor Mather and *his* Nobel Prize!

]]> By: Richard Bindel http://www.nuclearblog.org/2008/02/19/time-machine-possible-in-new-particle-accelerator/#comment-77 Richard Bindel Fri, 20 Jun 2008 20:36:59 +0000 http://www.nuclearblog.org/2008/02/19/time-machine-possible-in-new-particle-accelerator/#comment-77 The LHC will undoubtedly have lots of attention as scientists search for the Higgs boson (the “god particle”) using proton-proton collisions. For my part, I want to see the results when they start colliding large nuclei. Smash these together at LHC and there will be so many particles produced that, initially, they’ll barely move without bumping into each other. Or, who knows? Maybe the particles (probably quarks) will just sail by each other without interacting. We know that at RHIC, they apparently interact very strongly. They jostle around so much that they equilibrate locally, and you can use thermodynamics to understand them in bulk. In fact, when they expand, it looks very much like a compressed little droplet of liquid flowing outward, so hydrodynamics is used to understand the stuff. At the predecessors to LHC, this liquid expansion (it’s called elliptic flow) grew stronger and stronger as they cranked up the collision energy. At the top RHIC energy, the expansion was so strong that it looked like a liquid droplet with almost zero viscosity. Probably before that, it was sort of liquid-like but it wasn’t a completely thermal system. But now people think that the elliptic flow can’t get any bigger, because you can’t get any more liquidy than a zero viscosity liquid! So, at LHC I’ll be looking to see if the RHIC people got it right. Is this really hot nuclear matter a zero-viscosity liquid, in which case the elliptic flow won’t grow? Or did they get it wrong, and it just keeps getting bigger as the collision energy dial is turned up? (I know, I know... there’s no dial. They probably have a LabView vi instead.) The LHC will undoubtedly have lots of attention as scientists search for the Higgs boson (the “god particle”) using proton-proton collisions. For my part, I want to see the results when they start colliding large nuclei. Smash these together at LHC and there will be so many particles produced that, initially, they’ll barely move without bumping into each other. Or, who knows? Maybe the particles (probably quarks) will just sail by each other without interacting. We know that at RHIC, they apparently interact very strongly. They jostle around so much that they equilibrate locally, and you can use thermodynamics to understand them in bulk. In fact, when they expand, it looks very much like a compressed little droplet of liquid flowing outward, so hydrodynamics is used to understand the stuff. At the predecessors to LHC, this liquid expansion (it’s called elliptic flow) grew stronger and stronger as they cranked up the collision energy. At the top RHIC energy, the expansion was so strong that it looked like a liquid droplet with almost zero viscosity. Probably before that, it was sort of liquid-like but it wasn’t a completely thermal system. But now people think that the elliptic flow can’t get any bigger, because you can’t get any more liquidy than a zero viscosity liquid!

So, at LHC I’ll be looking to see if the RHIC people got it right. Is this really hot nuclear matter a zero-viscosity liquid, in which case the elliptic flow won’t grow? Or did they get it wrong, and it just keeps getting bigger as the collision energy dial is turned up? (I know, I know… there’s no dial. They probably have a LabView vi instead.)

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