Re: Question About Charged Particles.

[Jack Uretsky <jlu@HEP.ANL.GOV>]

Hi all-
        I was about to add to my previous message when this came in.

On Sun, 8 Apr 2001, Robert B Zannelli wrote:

>             I believe that my question has produced some helpful responses.
> If I understand the points made correctly, Jack Uretsky holds the opinion
> that a theory which incorporates electrically charged massless particles is
> possible

        I have exhibited such a theory (see the Schwinger reference -and
set the rest mass to zero).

> but he suspects that in order for the theory to be consistent
> massless particles may have to be confined. John S. Denker finds no intrinsic
> reason why QM would not allow massless charged particles. He takes the very
> clever approach of taking a charged particle like an electron and continue to
> reduce it's rest mass. The question to ask is, at what point in this weight
> loss program do we produce inconsistencies with known laws of physics. ( Here
> I equate mass and weight for the sake of pun)
>
>          John also makes the point, which I agree with, that one road to
> answering this question is to get beyond the standard model and come up with
> a theory that could calculate particle masses from first principals.  Of
> course this a tall order.
>  Nevertheless if I understand Gordon Kane of the University of Michigan
> correctly (I am just starting to look into his work) a successful theory
> incorporating Supersymmetry may be able to do this. This theory should give
> us a better understanding of the Higgs mechanism which is closely related to
> my question I believe.
        Yes, Gordon is a high priest of supersymmetry.  But no one that I
know of has proposed that supersymmetry is the road to understanding
particle masses.  Quite the opposite.  It is the string theorists who
believe that they are on the road to a "theory of everything".

>     Jack Uretsky has made the comment that in Physics, arguments from
> authority are worthless. Of course he is correct. Nevertheless it is also
> true that when certain people offer their opinion on a subject that by virtue
> of talent and education they are experts on, one should listen very carefully
> to what they say. Both John and Jack fall into this category and I am
> grateful for their responses. I find it interesting that even though Jack
> said the question was without meaning he was still able to offer a very
> reasoned response.
>
>    I would like to respond to Jack's point on the value of this question.
> There are certainly meaningless questions. If I were to ask if it were true
> that the Universe was made in seven days by a loving but stern father figure
> and that he planted evidence to fool us into thinking the whole thing took 15
> billion years that would be a meaningless question. It would be meaningless
> because there is no possibility of disproving it so this question has no
> value. I do not believe that my question falls into this category at all.
>
>         First to be consistent, the standard model requires massless
> particles with the observed masses being due to the Higgs mechanism.
> Shouldn't we be sure we can say this and be consistent?

        Consistent with what?  The Higgs mechanism was fine in the context
in which it was invented.  When applied to Quantum field theory the rules
became a bit vague.  QCD is the extant preferred theory of matter, and
we don't really know how to calculate with it.

> If not, then how do
> we deal with this question in the standard model?  Jack points out that in a
> later post that we don't even know what electric charge is.

        You've got the wrong guy.  Didn't happen on my watch.

> This is true, but
> to be fair how much do we really know about any of the terms we use to
> describe reality. Mass, spin etc. To me this sounds like a philosophic
> question, not a question we should be dealing with when we talk physics.
>
>            Finally we do have zero rest mass particles which carry color
> charge (they are confined by this force) and we did not question a massless
> neutrino with weak charge. Now we strongly suspect that neutrinos are not
> massless. So perhaps we can redefine the question, must all zero mass charged
> particles be confined, as Jack suspects?

        I don't like the term "must".  It smacks of the belief that there
are some eternal verities that govern our thinking.  That, in fact, is
what troubles me about this whole discussion.  I regard us as model
builders, and the restrictions imposed on any given model depend upon
the assumptions made in building that model.  Thus, I can understand the
question, "Can I make a model in which charged particles are massless?".
I might not be able to answer it, but I at least understand what it is
that I am supposed to do.
        A very different question is, "Can a charged particle be
massless?".  That is a question about all possible universes, so I suppose
that I would have to answer, "Yes, if the gods so will it."



> This may be worth thinking about
> too.
>
> Bob Zannelli
> New York
                        Regards,
                                        Jack
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