- #1
MMS
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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
MMS said:in the LHC t quarks are formed in pairs of t tbar.
ChrisVer said: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.MMS said:While I'm at it, how would a Feynman diagram look for, say, the first ttbar decay?
Thank you!mfb 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?mfb 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.
MMS said: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?
mfb 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.
Orodruin said: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...MMS said:So the arrows on the W+ decay on each of the 3 ttbar decays is opposite?
MMS said: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 <-.MMS said: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:MMS said: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.MMS said:Or in general, how can I tell the difference between a decay and simply an interaction?
ChrisVer said: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) ...
mfb said: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.mfb said: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.
Orodruin said: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 ...)Vanadium 50 said:I agree, but it's also important to get the arrow right so you write down the right wavefunction.
The Higgs production process from t-tbar refers to the creation of Higgs bosons from the collision of top and anti-top quarks. This process is one of the main ways in which Higgs bosons are produced in particle accelerators such as the Large Hadron Collider (LHC).
The production of Higgs from t-tbar is important because it provides a direct way to study the properties of the Higgs boson. By studying the production process, scientists can gain a better understanding of the Higgs boson's interactions with other particles and potentially uncover new physics beyond the Standard Model.
The production of Higgs from t-tbar is measured by detecting the decay products of the top and anti-top quarks. These decay products can include other particles such as W bosons, which can then further decay into other particles that can be detected by particle detectors.
One of the main challenges in studying the production of Higgs from t-tbar is the relatively low production rate compared to other processes. This means that a large number of collisions are needed to produce enough Higgs bosons for analysis. Additionally, the detection of the decay products can be complex and require advanced particle detectors.
The knowledge gained from studying the production of Higgs from t-tbar can be applied in many areas of particle physics. It can help improve our understanding of the Higgs boson and its role in the Standard Model, as well as potentially uncovering new physics beyond the Standard Model. This knowledge can also have practical applications in fields such as technology and medicine.