Changes between Version 2 and Version 3 of Models/HiggsEffective


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Timestamp:
03/28/13 18:46:49 (6 years ago)
Author:
omatt
Comment:

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  • Models/HiggsEffective

    v2 v3  
    3030== The non-propagating auxiliary particle T ==
    3131
    32 To describe the four-gluon-Higgs coupling a vertex with 5 external lines is needed. This cannot be done with !MadGraph. However, there is a way to circumvent this problem by introducing non-propagating auxiliary particles. It is possible to rewrite the four-gluon interactions as two three-point interactions connected by the new auxiliary tensor particle (called tn internally, and shows as T in the MG diagrams, the PDG code is 99). The troublesome five-point interaction (between the four gluons and the Higgs) reduces then to three three-point interactions.
     32To describe the four-gluon-Higgs coupling a vertex with 5 external lines is needed. This can be done with !MadGraph5 (But not with !MadGraph4). However, there is a way to circumvent the !Madgraph4 problem by introducing non-propagating auxiliary particles. It is possible to rewrite the four-gluon interactions as two three-point interactions connected by the new auxiliary tensor particle (called tn internally, and shows as T in the MG diagrams, the PDG code is 99). The troublesome five-point interaction (between the four gluons and the Higgs) reduces then to three three-point interactions.
    3333
    3434Notice that the color part of the four-gluon vertex is exactly like the sum of the s-, t-, and u-channel exchange diagram, where the exchanged particle is in the adjoint representation of color, i.e. an octet.