Recently discovered ZZ diboson

  • Thread starter Dmitry67
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In summary, the Z boson interaction terms are almost identical to the photon terms, but there is an extra factor of \cot\theta_w that accounts for the W+ and W-.
  • #1
Dmitry67
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I know about fermions forming pairs, but I had never heard about the bosons doing it.

Why 2 Z bosons interact (contrary to 2 photons)?
How do we know that we detected 1 ZZ boson, not 2 independent interactions with single Z bosons?
 
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  • #2
I presume you are meaning something related to this measurement?

http://www.fnal.gov/pub/today/archive_2008/today08-08-21.html

Nobody has claimed that di-boson production implies a bound state. What is happening is illustrated by the feynman diagram here:

http://www.pd.infn.it/~dorigo/zzdecay.jpg

So you see, the initial fermion line (from quark anti-quark annihilation) radiates two Z bosons, which each in turn decay into whatever Zs can decay into. If each Z decays into the same thing (i.e. you get 4 electrons, 4 muons or 4 quarks), they are difficult to untangle. However, if you look for events where one Z decays to quarks, and the other decays to leptons (i.e. electron or muons, as taus look rather like quark jets), then you can find these events as quark jets and leptons are, generically speaking, detected in different subdetectors of an experiment. I have not mentioned neutrinos as you can't detect these at all (in a colliding HEP experiment at least)...

It is wrong to say that the Z bosons interact with themselves. The Z can, however, interact with the W+ and W-. As to why these gauge bosons can interact and the photon can't is a very interesting one. It boils down to the gauge structure of the underlying theory. The U(1) group of electromagnetism is an abelian group (meaning the generator - the fundamental description of the group - commute, i.e. G(1)G(2) = G(2)G(1)). However, in SU(2) x U(1), the electroweak group structure, the generators no longer commute (i.e. G(1)G(2) != G(2)G(1)). The non-commutation implies self interaction terms are allowed.
 
  • #3
Thank you for the good explanation!
 
  • #4
bomanfishwow said:
...

It is wrong to say that the Z bosons interact with themselves. The Z can, however, interact with the W+ and W-. As to why these gauge bosons can interact and the photon can't is a very interesting one. It boils down to the gauge structure of the underlying theory. The U(1) group of electromagnetism is an abelian group (meaning the generator - the fundamental description of the group - commute, i.e. G(1)G(2) = G(2)G(1)). However, in SU(2) x U(1), the electroweak group structure, the generators no longer commute (i.e. G(1)G(2) != G(2)G(1)). The non-commutation implies self interaction terms are allowed.

Actually, the photon can interact with the W+ and W- just like the Z can. The interaction is almost identical, except that the ZWW coupling has an extra factor of [tex]\cot\theta_w[/tex]. Recall that in the electroweak theory, the U(1) of electromagnetism is a subgroup of the full SU(2) x U(1).
 
  • #5
daschaich said:
Actually, the photon can interact with the W+ and W- just like the Z can. The interaction is almost identical, except that the ZWW coupling has an extra factor of [tex]\cot\theta_w[/tex]. Recall that in the electroweak theory, the U(1) of electromagnetism is a subgroup of the full SU(2) x U(1).

Yes indeed, I was talking explicitly about Z/W interaction terms - I didn't want to get into the fact the U(1)s are different in each case!
 

1. What is a ZZ diboson?

A ZZ diboson is a subatomic particle composed of two Z bosons, which are elementary particles that mediate the weak nuclear force. These particles were recently discovered through experiments at the Large Hadron Collider.

2. How was the ZZ diboson discovered?

The ZZ diboson was discovered through experiments at the Large Hadron Collider, which is a particle accelerator located in Switzerland. Scientists use this machine to accelerate particles to high energies and then collide them to study the resulting subatomic particles.

3. Why is the discovery of the ZZ diboson significant?

The discovery of the ZZ diboson is significant because it provides further evidence for the Standard Model of particle physics, which is the current understanding of subatomic particles and their interactions. It also helps to fill in gaps in our understanding of the fundamental forces that govern the universe.

4. What are the potential implications of the ZZ diboson discovery?

The discovery of the ZZ diboson could potentially lead to new advancements in our understanding of the universe, including the nature of dark matter and the unification of the fundamental forces. It may also have technological applications in fields such as medicine and energy production.

5. What further research is needed to understand the ZZ diboson?

Further research is needed to study the properties and behavior of the ZZ diboson, including its interactions with other particles and its role in the Standard Model. Scientists will also continue to search for other new particles and phenomena to further expand our understanding of the subatomic world.

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