Higgs Decay

PLuz

Hello,

I had a doubt about a specific Higgs boson decay.

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

Diagram 1.pdf

Diagram 2.pdf

Diagram 3.pdf

My question is: does the third diagram exist? I do know that the [itex]s[/itex] 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

Parlyne

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.

PLuz

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

fzero

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).

PLuz

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

mfb

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.