Why is W boson decay to tau leptons neglected in calculations?

[ribella]

TL;DR

decays of W boson

Why is generally the decay of the W boson to tau lepton not taken in the calculations?

 

[malawi_glenn]

Calculations of what?

 

[ribella]

for example, I want to calculate the cross-section of the process pp->W-W+->l- v l+ vb (Here, l is generally taken as electron and muon). Therefore, why is generally the decay of the W boson to tau lepton not taken in the calculations?

 

[mfb]

Tau decays before reaching the particle detector while electrons and muons cross it without decay (in almost all cases, for the muon). It's easy to study decays to electrons and muons together but reconstructing decays to taus needs a completely different approach. We do study W decays to taus, but separately from the other two leptonic decays.

 

[ribella]

thanks for your response.

 

[malawi_glenn]

In tau decays, we have to use the hadronic calorimeters of the detector, and we have missing energy from the neutrino. This is, as mentioned, not as clean signal as two niceley charged tracks.

 

[Vanadium 50]

I'm still a little fuzzy on the question.

If the question is "If we are interested in $W \rightarrow e \nu$, why do we not consider $W \rightarrow \tau \nu$. the answer is "because electrons are not taus". If the question is instead, why do we not consider $W \rightarrow \tau (\rightarrow e \nu \nu) \nu$, the answer is "sometimes we do and sometimes we don't; it depends on the problem we are working."

 

[RGevo]

Assuming a stable tau, the calculations are equivalent up to corrections of order (mtau/mw)^2, and therefore almost numerically equivalent.

As the others alluded to, since this particle is not stable, the experimental (and theoretical) reality is more complicated.