.Higgs Boson Decay: Does the Third Diagram Exist?

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    Boson Decay Diagram
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Discussion Overview

The discussion revolves around the decay process of the Higgs boson, specifically the decay channel H -> c + \bar{s} + W^- and the existence of a particular diagram associated with this decay. Participants explore theoretical aspects, including tree-level and one-loop contributions, as well as the implications of quark masses and coupling strengths.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the existence of a third diagram in the Higgs decay process, noting the mass constraints of the quarks involved.
  • Another participant asserts that the third diagram does exist, clarifying that the strange quark can be virtual and thus not on-shell.
  • A participant acknowledges the oversight regarding the W boson and thanks the previous contributor for the clarification.
  • Discussion includes the observation that the Higgs coupling strength varies with the mass of the particle-antiparticle pair, with the coupling to s\bar{s} being significantly smaller than that to c\bar{c} and W^+W^- pairs.
  • One participant notes the expectation that tree-level diagrams involving Hs\bar{s} and Hc\bar{c} contribute less than one-loop diagrams involving Ht\bar{t} for many decay channels.
  • A participant expresses interest in comparing contributions of each diagram to the total width of the Higgs boson, referencing experimental constraints from the LHC and LEP.
  • Another participant mentions that they have not seen this decay represented in branching fraction diagrams but suggests it might be included in the W boson decay channel.

Areas of Agreement / Disagreement

Participants exhibit a mix of agreement and disagreement regarding the existence and implications of the third diagram. While some affirm its existence under certain conditions, others raise questions about the contributions and relevance of different decay channels.

Contextual Notes

Participants discuss the limitations of their analysis based on the mass of quarks and the nature of virtual particles, as well as the potential for different decay channels to dominate under specific conditions.

PLuz
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Hello,

I had a doubt about a specific Higgs boson decay.

In the process H -> c+\bar{s}+W^-, where c is the charm quark, \bar{s} the anti strange quark, in tree level I wrote the diagrams sent in attachment.

View attachment Diagram 1.pdf

View attachment Diagram 2.pdf

View attachment Diagram 3.pdf

My question is: does the third diagram exist? I do know that the s quark can't decay to the charm quark since it's mass is inferior to the mass of the charm quark. But in that diagram the strange quark is virtual so...there comes my confusion...

Thank you
 
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Yes, it exists. The s can't be on-shell in that process; but, then, the c can't be on-shell in diagram 2 either, so there's not really that big a distinction.
 
oh you're right. I was so focused in the quarks' masses that I didn't even think about the W boson. Thank you very much
 
You should also note that the Higgs coupling scales with with the mass of the particle-antiparticle pair being coupled to. So the coupling to ##s\bar{s}## is far smaller than that to ##c\bar{c}##, which is itself almost two orders of magnitude smaller than the coupling to ##W^+W^-##.

It is actually expected that the tree-level diagrams involving ##Hs\bar{s}## and ##Hc\bar{c}## give a smaller contribution than the one-loop diagram involving ##Ht\bar{t}## for many decay channels (though perhaps not the one you are considering).
 
Indeed I was only considering tree level and this decays but that's really interesting.

I am to draw the contributions of each diagram and compare to the total width of the higgs in the not excluded regions by the LHC and LEP and that is a nice conclusion that I can take.

Thank you
 
I never saw this decay in any diagram of the branching fractions, but as I would expect H->WW->Wcs as dominating channel, it might be included in the WW part.

"not excluded regions" is basically some region close to 125 MeV now, and probably just 125 MeV +- resolution after the presentations next week.
 

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