##W' \rightarrow \tau \nu## not Jacobian?

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In summary, the spectrum of the ##W' \rightarrow \tau## decay mode is different than the ##W' \rightarrow (e/\mu) \nu## decay mode because of the additional neutrinos.
  • #1
ChrisVer
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I don't understand why the ##W' \rightarrow \tau \nu## doesn't show a Jacobian peak whereas the ##W' \rightarrow (e/\mu) \nu## decay modes do...??
Is it because the ##\tau## decays even further (before measured) and gives additional Missing Transverse Energy? Is it the same for [itex]W \rightarrow \tau \nu[/itex] and [itex]W \rightarrow (e/ \mu) \nu [/itex]?
 
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  • #2
If you reconstruct the τ, you'll get the same peak. If you take the decay products, your spectrum will look different because you are missing at least two neutrinos then. The spectrum then depends on the decay mechanism.
 
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So for larger invariant masses reconstructions you will have a "Jacobian" shape, while for lower the spectrum will become flatter (because of the extra neutrino)?
 
  • #4
What do you mean with "larger invariant masses reconstructions"?

Additional neutrinos smear out the spectrum. The remaining decay products and the initial neutrino don't have to be back to back any more.
 
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Did you read the associated paper (CMS-PAS EXO-12-011)? If not, why not? If so, why didn't you point us to it and the part in the paper you didn't understand?

The red and the blue show Jacobians. The red and the blue in the plot right under that show peaks and a low mass non-resonant tail. The green shows no peak in the lower plot, just the non-resonant part, so of course it won't show a Jacobian in the upper part.
 
  • #9
Vanadium 50 said:
No, this one: https://twiki.cern.ch/twiki/pub/CMSPublic/PhysicsResultsEXO12011/NUGIMShapePlot.png

yes, sorry, I misunderstood the "the plot right under that" + the context of the associated paper.
Vanadium 50 said:
The red and the blue show Jacobians. The red and the blue in the plot right under that show peaks and a low mass non-resonant tail. The green shows no peak in the lower plot, just the non-resonant part, so of course it won't show a Jacobian in the upper part.

So it seemed to me and that's weird.
It seems that it's not true that we don't expect a Jacobian peak from the W'->tau nu, but whether we expect one or not depends on the ##\theta_E## of the W' (that's what the colored lines are for)...
##\theta_E## is somewhat connected with how large/small the couplings to the two light and the heavy generations are and so the Universality of the model. If ## \cot \theta_E = 1## then the couplings to the generations are universal (NUGIM= SSM), whereas for other values the coupling to tau or to e/mu is enhanced.

and it seems that as the cotangent approaches 1 (SSM) we get the Jacobian shape...
 
  • #10
While the post is tagged "A" so that most readers sophisticated enough to understand it would know, it does bear a mention that a W' is a hypothetical BSM particle that is being searched for at the LHC and elsewhere, and that this paper merely describes one version of this hypothetical particle, rather than an actually observed phenomena.
 
  • #11
ohwilleke said:
While the post is tagged "A" so that most readers sophisticated enough to understand it would know, it does bear a mention that a W' is a hypothetical BSM particle that is being searched for at the LHC and elsewhere, and that this paper merely describes one version of this hypothetical particle, rather than an actually observed phenomena.

Yes, the ##W^\prime## is an hypothetical particle which is predicted by some BSM physics...
Such a BSM is the [itex]SU_h(2) \times SU_l(2) \times U_Y(1)[/itex], which breaks down to the SM... Since no BSM physics has been found, this is an hypothetical model...and the "prediction" figures are obtained from simulations (the plot under discussion states it in the upper left corner)..
 

1. What is the significance of "##W' \rightarrow \tau \nu##" in particle physics?

"##W' \rightarrow \tau \nu##" refers to the decay of a hypothetical particle called W prime (W') into a tau lepton (##\tau##) and a neutrino (##\nu##). This process is of interest to particle physicists because it can provide insights into the properties and interactions of the W' particle, which could potentially exist beyond the Standard Model of particle physics.

2. How does the decay of "##W' \rightarrow \tau \nu##" differ from the decay of "##W \rightarrow \tau \nu##"?

The main difference between "##W' \rightarrow \tau \nu##" and "##W \rightarrow \tau \nu##" is that the W' particle has a higher mass compared to the W particle. This means that the decay of W' produces a tau lepton with higher energy, which can be observed in experimental data. Additionally, the W' particle is predicted to have different decay rates and branching ratios compared to the W particle, providing important information for testing theoretical models.

3. What are the current experimental results for "##W' \rightarrow \tau \nu##"?

Currently, there is no experimental evidence for the existence of the W' particle, so the decay "##W' \rightarrow \tau \nu##" has not been observed. However, several experiments, such as the Large Hadron Collider (LHC) at CERN, are actively searching for the W' particle and its decays, which could provide insights into new physics beyond the Standard Model.

4. What are the potential implications of observing "##W' \rightarrow \tau \nu##" in experiments?

If the decay "##W' \rightarrow \tau \nu##" is observed in experiments, it would be a groundbreaking discovery, providing evidence for the existence of the W' particle and potentially indicating the presence of new physics beyond the Standard Model. This could open up new avenues for research and further our understanding of the fundamental building blocks of the universe.

5. How does the decay "##W' \rightarrow \tau \nu##" relate to the Higgs boson?

The Higgs boson, which was discovered in 2012 by the LHC, is another important particle in particle physics. The decay "##W' \rightarrow \tau \nu##" is predicted to occur at a similar rate to the decay of the Higgs boson into a tau lepton and a neutrino. Therefore, studying the decay "##W' \rightarrow \tau \nu##" can provide insights into the properties and interactions of the Higgs boson, as well as potentially revealing new physics beyond the Standard Model.

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