Re: [Phys-L] Particle physics

[Bill Nettles <bnettles@uu.edu>]

> -----Original Message-----
> From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Paul Lulai
> Sent: Tuesday, June 18, 2013 2:02 PM
> To: Phys-L@Phys-L.org
> Subject: Re: [Phys-L] Particle physics


> Fundamental particles have no constituent parts. We believe leptons,
> quarks, and some bosons are fundamental.

JD (as much as I appreciate and anticipate his explanations) ignored the first sentence here. If we take that as a definition of a "fundamental particle", (see _The Physics of Nuclei and Particles_  by Richard Dunlap) then based on the Standard Model, leptons, quarks,  and gauge bosons would (today) be classified as "fundamental."  We have no experimental evidence of internal structure. I'm not aware of models other than string theory that propose internal structure for them, but I don't peruse ArXiv looking for such papers :).

> Is the Higgs boson fundamental?  I thought it must be, but that is simply
> because it felt like it must be if it is what the Higgs field uses to interact with
> particles to give them mass.  Since I am going on feelings, I don't trust them.
> Dan addresses this to a certain extent.  My interpretation, 'The Higgs seems
> to be as fundamental as anything else, however, we simply might not have
> the resolution to see anything smaller just yet.'  So I feel somewhat at
> (perhaps temporary) peace with this point.

Not sure what you mean by smaller.  The mass of a Higgs boson is expected to be in the 100-200 GeV range, whereas a proton has a mass less than 1 GeV. The difference is the free-particle stability. A Higgs boson quickly decays, and the proton doesn't.  The Higgs decay channels involve gauge bosons (W+/W- pairs, photons, Zo) and end up with leptons.  I haven't found anything which says Higgs is or isn't fundamental, but maybe I'm missing something in my reading.  From what I've gathered it seems the theorists don't believe there is any "reason" for Higgs to have structure.  Fundamentally, the Higgs boson is simply a point-mass manifestation showing the existence of the Higgs field, the field being the all-important idea that particle physicists are trying to confirm.  It's kind of like the search for the positron or gravitational lensing. The model predicts it should be there, so let's look for it to see how powerful this model is.

> Another cleaning up of my language, discussing the creation of a particle,
> energy, charge, momentum, lepton number (possibly baryon number) are
> conserved.  If one runs a proton - proton collision, are all of the particles
> detected just the rearrangement of the quarks and bosons present in the
> initial protons?  Are some created as the result not of the reaarangement of
> particles, but as a result of (really bad phrasing here) leftover energy?  I
> understand that some of the energy would simply go to the kinetic energy of
> the particles.

Consider the p + p -> p + p + p + p_ (antiproton) reaction.  You certainly don't have a mere rearrangement of  quarks. You have some new quarks.  What you do have is conservation of quark number (where the antiproton has antiquarks which count as -1), baryon number (2), lepton number along with energy, momentum, etc. That's just a simple reaction, and there are gobs more that other channels with "new" quarks and antiquarks.

> I think this would likely not be simply the rearrangement of particles since
> positron - electron collisions also produce particles.

Yes

> The above questions lead to what maybe should have been the only
> question I asked, but the question I am trying to resolve.  I guess I am
> wondering if within the accelerator & detector, is there something like pair
> production happening?  If so, what would be the other half of the pair
> produced with the Higgs Boson?  Quick answer would be the anti-Higgs, but
> that is so knee-jerk that I feel I should put it back in my mouth and fingertips
> before I send the note.  If there is not pair-production, then is everything
> either the re-arrangement of existing particles (with some color changing of
> quarks possible) along with some decay processes to more stable particles?
>
> Thanks for your time and help.
>
> Paul.
>
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