Re: What is the Standard Model

From: Alfred Einstead (whopkins_at_csd.uwm.edu)
Date: 06/12/04 

Date: 12 Jun 2004 15:00:07 -0700

reany@asu.edu (Patrick Reany) wrote:
> Recently, Bilge and I had a disagreement about what is meant by the
> so-called Standard Model of particle physics.

There is no room for disagreement in any direction.

The Standard Model is that which is given by the Standard Model
Lagrangian, which is listed (for instance) in the SLAC web site.
The Lagrangian is that for a Yang-Mills-Higgs field theory with a
U(1) x SU(2) x SU(3) symmetry group, which acts also in a fermion
space in a specific way delimited there and in numerous other
places (the standard version of the SM has 90 fermion states;
there are 96 if neutrinos are regarded as ordinary 4-component
Dirac spinors). The Higgs field, likewise is acted on by the
symmetry group in a specific way delimited there and elsewhere;
and acts on the fermion part of the spectrum to give the appearance
of a mass matrix (and on the gauge bosons to do likewise) with
a specific decomposition into mass eigenstates and eigencvectors.

\
 What I'm interested in
> is the opinions of the readership about what they feel it means.
> Please choose from the choices below:
>
> 1) The Standard Model refers to the consensus of the best estimate at
> any given moment of the behavior of particles from a quantum
> mechanical viewpoint which includes electroweak and stong force
> particles; this consensus includes specifying particles mass of all
> "known" particles. Thus the Standard Model is a theory, not just a
> framework.
>
> 2) The Standard Model refers to the consensus of the best fixed
> framework to theorize about the behavior of particles from a quantum
> mechanical viewpoint which includes electroweak and stong force
> particles; this consensus does NOT include specifying all particles
> mass. In other words, the Standard Model is a research program's
> formal point of view (a framework only, not a theory), which is itself
> incapable of making predictions until the masses are set independently
> of the framework.
>
> 3) Other. Please explain in detail.
>
> **********************************************
>
> Now, for some on-line references:
>
>
> http://www2.slac.stanford.edu/vvc/theory/model.html
>
> The Standard Model
> The Standard Model is the name given to the current theory of
> fundamental particles and how they interact. This theory includes:
>
> Strong interactions due to the color charges of quarks and gluons.
> A combined theory of weak and electromagnetic interaction, known as
> electroweak theory, that introduces W and Z bosons as the carrier
> particles of weak processes, and photons as mediators to
> electromagnetic interactions.
> The theory does not include the effects of gravitational interactions.
> These effects are tiny under high-energy Physics situations, and can
> be neglected in describing the experiments. Eventually, we seek a
> theory that also includes a correct quantum version of gravitational
> interactions, but this is not yet achieved.
>
> The Standard Model was the triumph of particle physics of the 1970's
> . It incorporated all that was known at that time and has since then
> successfully predicted the outcome of a large variety of experiments.
> Today, the Standard Model is a well established theory applicable over
> a wide range of conditions.
>
>
>
> -----------------------------------------------------
>
> http://particleadventure.org/particleadventure/frameless/standard_model.html
>
> Physicists have developed a theory called The Standard Model that
> explains what the world is and what holds it together. It is a simple
> and comprehensive theory that explains all the hundreds of particles
> and complex interactions with only:
>
> 6 quarks.
> 6 leptons. The best-known lepton is the electron. We will talk about
> leptons in just a few pages.
> Force carrier particles, like the photon. We will talk about these
> particles later.
>
> -----------------------------------------------------
> http://en.wikipedia.org/wiki/Standard_Model
>
> The Standard Model of particle physics is a theory which describes the
> strong, weak, and electromagnetic fundamental forces, as well as the
> fundamental particles that make up all matter. It is a quantum field
> theory, and consistent with both quantum mechanics and special
> relativity. To date, almost all experimental tests of the three forces
> described by the Standard Model have agreed with its predictions.
> However, the Standard Model is not a complete theory of fundamental
> interactions, primarily because it does not describe gravity..........
>
> Although the Standard Model has had great success in explaining
> experimental results, it has never been accepted as a complete theory
> of fundamental physics. This is because it has two important defects:
>
> The model contains 19 free parameters, such as particle masses, which
> must be determined experimentally (plus another 10 for neutrino
> masses). These parameters cannot be independently calculated.
>
> [My comment: I doubt that the particle masses are uniquely determined
> by experiment.]
>
>
> -----------------------------------------------------
> http://www.lns.cornell.edu/public/lab-info/quark.html ******
>
> In recent years, high energy physicists have arrived at a picture of
> the microscopic physical universe, called "The Standard Model", which
> unifies the nuclear, electromagnetic, and weak forces and enumerates
> the fundamental building blocks of the universe:
>
> 6 leptons:
> electron, electron neutrino
> muon, muon neutrino
> tau, tau neutrino
> 6 quarks:
> d (down), u (up)
> s (strange), c (charm)
> b (bottom), t (top)
> Ordinary matter is made of protons (each a u-u-d quark triplet),
> neutrons (each a u-d-d quark triplet), and electrons. Quarks cannot
> exist singly (or so it appears), so the particles created in
> accelerator collisions include mesons (combinations of a quark and an
> anti-quark), baryons (combinations of three quarks), and leptons. All
> but the proton, electron and neutrinos are unstable and decay to the
> stable particles. In the Standard Model the forces are communicated
> between particles by the exchange of quanta which behave like
> particles:
>
> 4 intermediate vector bosons:
> gluon (nuclear force)
> photon (electromagnetic force)
> W and Z bosons (weak force)
> In principle, the model can predict the outcome of any experiment (or
> the probabilities of the various possible outcomes), but in most cases
> of interest the theoretical calculations are too complicated to be
> carried out with current techniques.
>
> [My comment: If the model can predict the outcome of any experiment,
> it must contain a commitment to particle masses! There seems to be
> some confusion about what the "Model" really is, and it has affected
> more than just me.]
> -----------------------------------------------------
>
> http://superstringtheory.com/experm/exper2.html
>
> Through a combination of theory and experiment, a mathematical model
> that describes or explains all particle physics observed so far by
> physicists has been worked out. This model is called the Standard
> Model. From the experimental point of view, the Standard Model is
> studied and confirmed so well that things are, well, almost boring.
>
> [My comment: Same as last.]
> -----------------------------------------------------
> http://zebu.uoregon.edu/~js/glossary/standard_model.html
>
> The Standard Model is the combination of two theories of particle
> physics into a single framework to describe all interactions of
> subatomic particles, except those due to gravity. The two components
> of the standard model are electroweak theory, which describes
> interactions via the electromagnetic and weak forces, and quantum
> chromodynamics, the theory of the strong nuclear force. Both these
> theories are gauge field theories, which describe the interactions
> between particles in terms of the exchange of intermediary "messenger"
> particles that have one unit of intrinsic angular momentum, or spin.
>
>
> [My comment: framework is not a theory.]
> -----------------------------------------------------
>
> So, is the Standard Model a framework or a theory? I really don't care
> which it is. I just want to know. But I will propose this: The
> Standard Model ought to be considered an evolving theory which is
> accountable for all experimental tests brought against it. That is, it
> is capable of being formally "falsified," in which case it has to
> evolve into a new "version" of the Model. But all I require is that
> people not confuse a "framework for building a theory" and a theory.
>
> Patrick

Relevant Pages

  • This Weeks Finds in Mathematical Physics (Week 253)
    ... This Week's Finds in Mathematical Physics ... particles using some math called "triality", ... Standard Model, together with gravity. ... makes the Lie algebra suinto a Lie subalgebra of so. ...
    (sci.math.research)
  • Re: What is the Standard Model
    ... Let's look at what the standard model is and is not - and how it got ... Here physics takes a course that seems to be foreign to a certain ... Anyway, what we have now, is the electroweak theory as first proposed ... extension to the electroweak that includes the u and d quark along ...
    (sci.physics.relativity)
  • Re: What is the Standard Model
    ... Let's look at what the standard model is and is not - and how it got ... Here physics takes a course that seems to be foreign to a certain ... Anyway, what we have now, is the electroweak theory as first proposed ... extension to the electroweak that includes the u and d quark along ...
    (sci.physics)
  • What is the Standard Model
    ... The Standard Model refers to the consensus of the best estimate at ... mechanical viewpoint which includes electroweak and stong force ... particles; this consensus includes specifying particles mass of all ... These effects are tiny under high-energy Physics situations, ...
    (sci.physics)
  • What is the Standard Model
    ... The Standard Model refers to the consensus of the best estimate at ... mechanical viewpoint which includes electroweak and stong force ... particles; this consensus includes specifying particles mass of all ... These effects are tiny under high-energy Physics situations, ...
    (sci.physics.relativity)