# Question about the decay of the W boson to tau lepton

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• ribella
In summary: However, in summary, the decay of the W boson to tau lepton is not always taken into account in calculations because it requires a different approach and the resulting signal is not as clean as with electrons and muons. Depending on the specific problem being studied, W decays to taus may or may not be considered, but in general, they are not as commonly included as the other two leptonic decays. This is due to the fact that taus decay before reaching the particle detector, making it more difficult to study their decays. Additionally, the use of hadronic calorimeters and the presence of missing energy from neutrinos adds further complications. However, for stable taus, the calculations are equivalent up to minor corrections.
ribella
TL;DR Summary
decays of W boson
Why is generally the decay of the W boson to tau lepton not taken in the calculations?

Calculations of what?

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?

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.

artis, vanhees71, topsquark and 1 other person

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.

artis, vanhees71 and topsquark
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."

vanhees71
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.

## 1. What is the W boson and why is it important?

The W boson is a subatomic particle that is responsible for the weak nuclear force, one of the four fundamental forces in the universe. It plays a crucial role in the process of radioactive decay and is important in understanding the structure and behavior of matter.

## 2. What is the decay of the W boson to tau lepton?

The decay of the W boson to tau lepton is a process in which the W boson transforms into a tau lepton, a heavier cousin of the electron. This decay is one of the possible outcomes of the weak interaction and is important in studying the properties of the W boson and the tau lepton.

## 3. How does the decay of the W boson to tau lepton occur?

The decay of the W boson to tau lepton occurs through a process called weak decay, in which the W boson emits a virtual particle called a virtual W boson. This virtual W boson then decays into a tau lepton and its corresponding neutrino. This process is governed by the laws of quantum mechanics and is a random event.

## 4. What is the significance of studying the decay of the W boson to tau lepton?

Studying the decay of the W boson to tau lepton allows scientists to test the predictions of the Standard Model, which is the current theory that explains the behavior of particles and their interactions. Any discrepancies between the observed decay rate and the predicted rate could indicate the presence of new physics beyond the Standard Model.

## 5. Can the decay of the W boson to tau lepton be observed in experiments?

Yes, the decay of the W boson to tau lepton has been observed in experiments at particle accelerators such as the Large Hadron Collider (LHC). By measuring the properties of the decay products, scientists can confirm the existence of the W boson and study its behavior in detail.

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