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Hello
What possible processes are there for a production of Higgs from t-tbar?
Thanks you in advance
What possible processes are there for a production of Higgs from t-tbar?
Thanks you in advance
in the LHC t quarks are formed in pairs of t tbar.
Also what's the difference in the ttbar decays you posted?
Both top decay to Wb, the W then decay either to lepton+neutrino or quark+antiquark.While I'm at it, how would a Feynman diagram look for, say, the first ttbar decay?
I'm trying to draw the actual diagram like you said and I'm kind of struggling to do so. Can you please show me the actual diagram with what you said?There is also ##t \bar t \to b \bar b q \bar q q \bar q## but it is a tricky channel experimentally.
Both top decay to Wb, the W then decay either to lepton+neutrino or quark+antiquark.
I'm trying to draw the actual diagram like you said and I'm kind of struggling to do so. Can you please show me the actual diagram with what you said?
Correct.
And all the other decay modes work in the same way.
Edit: Didn't check the arrows. Orodruin is right, some of them point in the wrong direction.
Your fermion flows are not correct. You should take care in which way the arrows of your fermion lines go. In the standard model, the fermion flow never changes direction.
Ws don't need an arrow...So the arrows on the W+ decay on each of the 3 ttbar decays is opposite?
Maybe this is something basic that I am missing out on but assuming I draw the antiparticle arrows in the opposite direction, how can one tell that it's a decay of ttbar that we're talking about?
well in your plot there are 2 arrows moving out from a "vertex".... [have a look at ttbar]... of course the tops don't come from the same vertex, but still.... the idea is again the one I mentioned, particles -> antiparticles <-.I thought an arrow going in and one out means that there is an interaction between the two particles.
A decay is pretty simple an interaction that looks like this:Or in general, how can I tell the difference between a decay and simply an interaction?
If one particles come in and multiple go out, the whole diagram is a decay, otherwise the more general "interaction" is used.Or in general, how can I tell the difference between a decay and simply an interaction?
Arrows don't necessariy show the flow of the interaction. They are there corresponding to some mathematical quantity, as are the Feynman Diagrams... they roughly tell you what kind of Dirac spinors you are using. In some interpretation, the antiparticles move "backwards in time", although that's an interpretation and shouldn't be taken literally in the same way as the Feynman diagrams shouldn't be literally taken as the physical interaction, so in that view it's natural to draw them like that...[in order to have a flow]
well in your plot there are 2 arrows moving out from a "vertex".... [have a look at ttbar]... of course the tops don't come from the same vertex, but still.... the idea is again the one I mentioned, particles -> antiparticles <-.
A decay is pretty simple an interaction that looks like this:
[itex]1 \rightarrow 2+3+...+N[/itex]
An interaction though should have at least 2 particles in the initial state....
Although a decay is an interaction too [eg the particle 1 decays via an interaction to the particles 2,3...N) ...
If one particles come in and multiple go out, the whole diagram is a decay, otherwise the more general "interaction" is used.
Antiparticles always have their arrows go against the time direction. You can tell it's a ttbar process (including the decays of the tops) because you start with ttbar production (the production process is currently not part of your diagrams) and you have different outgoing particles.
I just want to point out that it is essentially pointless to interpret the "time direction" of internal lines and assign particle/antiparticle lables to them. The Feynman diagram is a pictorial representaton of terms in a perturbative expansion of a path integral. For example, we do not draw separate diagrams to represent W- exchange in one direction and W+ in the other. They are the same diagram representing the same term in the expansion.Antiparticles always have their arrows go against the time direction. You can tell it's a ttbar process (including the decays of the tops) because you start with ttbar production (the production process is currently not part of your diagrams) and you have different outgoing particles.
I just want to point out that it is essentially pointless to interpret the "time direction" of internal lines and assign particle/antiparticle lables to them.
Indeed, never reverse the direction of a fermion line! (In the Standard Model ...)I agree, but it's also important to get the arrow right so you write down the right wavefunction.