XPost: sci.physics   
   From: bodkinodd@gmail.com   
      
   On 3/5/2017 5:39 PM, Norm X wrote:   
   >> An isolated neutron will on average, in its own rest frame, decay into an   
   >> electron and a proton in less than 15 minutes. The electron is an   
   >> indivisible particle, while the proton is not.   
   >>   
   >> The nucleus of all atoms except hydrogen, is some kind of ensemble of   
   >> protons and neutron, bound by the strong nuclear force. Isolated protons   
   >> and neutrons are each identical particles. This may be true even if they   
   >> are not isolated.   
   >>   
   >> According to the standard model, protons and neutron are each some kind of   
   >> ensemble of quarks, bound by the strong nuclear force.   
   >>   
   >> Question: to what extent can we consider the nucleus an ensemble of quarks   
   >> without recourse to the proton/neutron description of the nucleus?   
   >>   
   >> Thanks.   
   >   
   > Supplementary question:   
   >   
   > Which is better, the proton/neutron description or the quark soup model, for   
   > prediction of observables, like the scattering diameter of a nucleus? On the   
   > other hand, are any such observables, useful for refinement of the strong   
   > nuclear force in the standard model?   
      
   Well, as I said, which model is better depends on the energy scale   
   you're looking at it.   
      
   For nuclear interactions, like fission and the like, the energies   
   involved are around a tenth of the proton mass at most, and so then the   
   low-energy treatment works just fine. For proton-proton scattering at,   
   say, the LHC, though, the high-energy treatment works better. At these   
   latter scales, in fact, the "scattering diameter of the nucleus" becomes   
   almost irrelevant, because you're really just looking at the scattering   
   of one quark against another quark, or a gluon against a gluon, or a   
   gluon against a quark.   
      
   The analogy would be if you got two purse-sixed burlap bags, and in each   
   you put three steel ball bearings. Now put the bags in two launchers and   
   fire them at each other. If you use slingshots as the launchers, then   
   you'll see one bag bouncing off another bag, and the rattling around of   
   the ball bearings inside won't change things much. But if you fired them   
   out of high-speed cannons, then the impact would most likely be one ball   
   bearing bouncing off one other ball bearing (the purses being big enough   
   that it's unlikely that two pairs would collide in the same firing), the   
   recoiling balls breaking loose from the burlap bags as though they   
   weren't even there.   
      
   >   
   > Thanks again.   
   >   
   >   
      
      
   --   
   Odd Bodkin -- maker of fine toys, tools, tables   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)