Self-energy Operator

[Simon Peach]

This a quote from Nature of the 30 of june 2022
'Like the electron, the muon has a magnetic field that makes it act like a tiny bar magnet. As muons travel, they generate various particles that briefly pop in and out of existence."
Now I would like to know how 'various particles' pop in and out of existence. Surely this carn't be correct as matter carn't be created form nothing?

 

[Orodruin]

Please link to the original article.

 

[malawi_glenn]

@Orodruin here: https://www.nature.com/articles/d41586-022-01810-z


@Simon Peach : It is just a popular science description, it should not be taken too literarly.

Anyway, the article is referring to something called virtual particles, which are not real - they are only calculational tools when computing things in perturbative quantum field theories.
This is a more of a professional description https://en.wikipedia.org/wiki/Self-energy
And here is anomalous magnetic dipole moment https://en.wikipedia.org/wiki/Anomalous_magnetic_dipole_moment

So, the muon can not only couple directly to a photon (mediator of the electromagnetic force), it can also couple via "loop" interactions, in which there are virtual particles - internal propagators. The popular science approach is to interpret those propagators as something that actually exists, but only for a short moment of time due to Heisenberg uncertainty relation $\Delta E \Delta t > h / 4 \pi$

Sounds way cooler to talk about "virtual particles that violates energy conservation but only for a short period of time" than "internal propagators which are to be integrated over the entire momentum space..."

 

[Orodruin]

@Orodruin here: https://www.nature.com/articles/d41586-022-01810-z

Oh, I could have found it if I made the effort to search for it. My point is that I should not have to and neither should you, it should have been provided in the OP.

@A. Neumaier has a couple of Insights on the topic of virtual particles:
https://www.physicsforums.com/insights/physics-virtual-particles/
https://www.physicsforums.com/insights/misconceptions-virtual-particles/

 

[ohwilleke]

This a quote from Nature of the 30 of june 2022
'Like the electron, the muon has a magnetic field that makes it act like a tiny bar magnet. As muons travel, they generate various particles that briefly pop in and out of existence."
Now I would like to know how 'various particles' pop in and out of existence. Surely this carn't be correct as matter carn't be created form nothing?

The calculation involves considering every possible way consistent with the rules of particle physics that something can happen, disregarding whether there is sufficient mass-energy to allow them to happen, and then modifies the weight given to possibilities with insufficient mass-energy (virtual particles) based upon how big the shortfall of mass-energy is.

It turns out that disregarding these seemingly impossible paths (since there is insufficient mass-energy for the particles imagined in the intermediate steps) gives you the wrong answer.

 

[malawi_glenn]

It is funny to note that the discovery of the Higgs boson uses two of these "loops" with virtual particles.

Production via gluon gluon fusion

Decay to a pair of photons

 

[Orodruin]

It is funny to note that the discovery of the Higgs boson uses two of these "loops" with virtual particles.

Production via gluon gluon fusion
View attachment 304092

Decay to a pair of photons
View attachment 304093

That’s a top class observation.



(Thank you, thank you, I’ll be here all week. Feel free to tip your waiters! )

 

[malawi_glenn]

That’s a top class observation.

I have to go to the bottom of this, seems rather strange.

 

[Orodruin]

I have to go to the bottom of this, seems rather strange.

Charming. Picked me up a bit, I was starting to feel down.

 

[malawi_glenn]

Charming. Picked me up a bit, I was starting to feel down.

I have to watch your replies again using my technicolor-VCR ... perhaps I can see some more structure

 

[vanhees71]

Well that's to be expected from the just upgraded LHC+detectors.

https://cerncourier.com/a/the-higgs-boson-under-the-microscope/

 

[Orodruin]

I have to watch your replies again using my technicolor-VCR ... perhaps I can see some more structure

I’ll go looking for my super-VHS tapes. I’m sure I’ll find them as soon as I turn on the light in my large circular basement.