Re: How do the Higgson and Higgsino interact with the w and z bosons.

Date: Wed Feb 11 09:31:06 1998
Posted By: Samuel Silverstein, faculty, physics, Stockholm University
Area of science: Physics
ID: 886447743.Ph

Message:

The Higgs particle (or particles...see below!) is postulated to answer the question of what gives particles their masses. To put the idea simply, the vacuum of space is hypothesized to be permeated by a "Higgs field", akin in some respects to, for instance, an electromagnetic field. Particles moving through space would interact with this field through the exchange of virtual Higgs bosons, and thus acquire mass. Particles which interact more strongly would appear to have more mass. This mechanism is built into the Standard Model of particle physics, as well as extensions of this model such as Supersymmetry.

You can see, then, that the Higgs boson must be able to interact with ANY massive particle in order to carry out its function. Your question is specific to the weak Z and W bosons, but the Higgs boson can couple with any boson (spin 0) or fermion (spin 1/2). The Higgs boson can even couple with itself! Of course, since the W and Z are so massive, the Higgs boson would be expected to couple more strongly to them. So, many current Higgs searches look for evidence of interactions such as:


Z -> H + Z*   /b _
             /__ b
e+     0    /
  \   Z    / H0
   >------<
  /        \  
e-           Z*

where the outgoing Z* then decays into a set of quarks or leptons. This is one of the searches being performed at LEP at the moment, but you should be able to see the basic point of the Higgs (H0) interactions here. Other examples of simple Feynman diagrams of H0 interactions would be:

_                       +                 +
q             +      / W               / W
 \_____      W _____/         H0 _____/
 /  H0              \                 \   -
q                    \ H0              \ W

Now, up to now I have been describing the Higgs boson of the Standard model, which is a scalar (no spin), neutral (no charge) boson with a yet undetermined mass. You also inquired about "Higgsinos", which I take to mean the Higgs bosons described in Supersymmetry (or SUSY), one of the most popular extensions of the Standard Model. In SUSY, each particle of the Standard Model has a supersymmetric partner (these partners have yet to be discovered by any particle physics experiment). The Higgs is no exception to this proliferation of particles; the minimal supersymmetric model has two scalar Higgs bosons:

  0    0
 H    H
  1    2

A pseudoscalar:

    0
   A

and a charged Higgs pair:

   +/-
  H

These Higgs bosons have interactions which resemble the ones I have already described, although the charged Higgs bosons have vertices which resemble more those of the weak W+/- bosons:

         / c  (charge +2/3)
  ______/
    +   \  _
   H     \ s  (charge +1/3)

and so forth. For experimental limits on different Higgs interactions, you could look at the information from the Particle Data Group at URL http://pdg.lbl.gov/ .

Other good references include a summary of posts on the sci.physics newsgroup, at http://www.hep.phy.cam.ac.uk/theory/ben/physics/higgs.html ,
as well as some well-written introductions to the Higgs mechanism, at
http://www.sciam.com/askexpert/physics/physics11.html , and
http://hepwww.ph.qmw.ac.uk/epp/higgs.html .

I hope this helps.

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