New Physics!

[sevenperforce]

23 hours ago, K^2 said:

In the way particles are usually interpreted in Standard Model, a particle has to be massless to be its own antiparticle. There's also the fact that neutrinos come with predominant handedness, and that strongly suggests that neutrinos and antineutrinos are distinct. (Otherwise, we'd expect equal distributions by CPT.) So there is strong indication that they probably aren't their own antiparticles. If we find an experiment that strongly suggests they are, we'd have some explaining to do.

But aren't the Z and Higgs bosons also their own antiparticles?

[K^2]

1 hour ago, sevenperforce said:

But aren't the Z and Higgs bosons also their own antiparticles?

Yeah, but they're bosons. They're allowed.  On a more serious tone, I should probably be distinguishing between current mass and dynamic mass. Z and Higgs' mass is entirely dynamically generated. All of the leptons have a non-zero current mass, as far as we can tell from the models. So the mass is inherent to the particle, not just consequence of its interaction with vacuum, as it is for neutral bosons. You can think of Z as a massless particle wearing very heavy jacket. In fact, the only reason photon is massless is because of the symmetry break due to Higgs mechanism. So it's less that photons have no mass, and more that we call the part of electro-weak interaction that ended up naked the "photons". And so it happens that electromagnetic interactions get an infinite range and infinite fame, and the weak part is, well, weak.

But yeah, we're definitely getting into the territory of interpretations, so things are bound to be fuzzy. And I don't remember last time I cared about whether something is a particle or anti-particle. If you aren't happy, flip the diagram over. If it's still not working for you, try turning the diagram 90°. That decay is a scattering problem now. How nice.

[Jacke]

7 hours ago, Gargamel said:

Part of me wonders though, since they’re using some of the same equipment in both excitements, if there is some instrumentation problems leading to these results.  

The only common component is the major superconducting magnet ring.  All the other hardware was new and improved.  And considering the difference is well into the significant digits, this really does appear to be significant.

I think the next steps will be a recreation of this and similar experiments, because that'll be a big career paper, either confirming this trend or refuting it.

Edited April 13, 2021 by Jacke

[sevenperforce]

3 hours ago, K^2 said:

Yeah, but they're bosons. They're allowed.  

Good point.

Quote

On a more serious tone, I should probably be distinguishing between current mass and dynamic mass. Z and Higgs' mass is entirely dynamically generated. All of the leptons have a non-zero current mass, as far as we can tell from the models. So the mass is inherent to the particle, not just consequence of its interaction with vacuum, as it is for neutral bosons. You can think of Z as a massless particle wearing very heavy jacket. In fact, the only reason photon is massless is because of the symmetry break due to Higgs mechanism. So it's less that photons have no mass, and more that we call the part of electro-weak interaction that ended up naked the "photons".

"Rest mass" I know, and "relativistic mass" I know, but what are "current mass" and "dynamic mass"?

At present my diagram just has a (?) exponent for the neutrinos.

EDIT:

**to clarify, I currently have a (0) exponent for the photon, Higgs boson, and Z boson, an (8) exponent for the gluon, a (+/-) exponent for the positively-charged leptons, a (-/+) exponent for the negatively-charged leptons, and then the aforementioned (?) exponent for the neutrinos because I have no freaking idea what they are.

Edited April 13, 2021 by sevenperforce

[K^2]

29 minutes ago, sevenperforce said:

"Rest mass" I know, and "relativistic mass" I know, but what are "current mass" and "dynamic mass"?

Current mass, also known as bare mass or naked mass, is the mass you have to attach to the underlying field itself, like, a mass a particle would still have if it interacted with absolutely nothing but gravity. Dynamic mass is what comes out from all the interaction. In the simplest terms, if you take an electron and you accelerate it, you aren't accelerating just the particle, but the electromagnetic field around it as well. So a particle with any sort of charge acts as if it's heavier, and in most contexts, that's the mass we actually care about. 511keV is the energy of electron itself plus all the vacuum junk that is dragged along with it. The reason this rarely comes up is because the electromagnetic correction to electron mass is less than 1%. But then constituent mass of quarks in a proton or neutron is almost entirely dynamic, with current mass of quarks being comparatively tiny.

 

On the thread topic, I just saw a pretty good video by Sixty Symbols on the muon shenanigans. Some of it is understandably hand-wavy, but it covers the bases, so it's a good watch.

 

One interesting thing they mention that might be raising some eyebrows is the fact that lattice QCD is done in Euclidian metric. The idea there is that you take time to be imaginary. This lets you replace Minkowski space-time with Euclidian space-time, but then every oscillation becomes a decay instead. The reason it's actually great is that contributions with higher energies decay faster. So as you evolve the system, such simulations tend towards ground state. Therefore, they are really good about answering questions about configurations of particles and vacuum in the ground state. Of course, you have to do a ton of math to convert between the two metrics and to get final results, but on the plus side, you don't have to try and solve a differential equation in 4 dimensions. Instead, you start with an arbitrary "guess" in 3 dimensions and evolve it until it's in the ground state, which is the solution you are looking for. And since the biggest limitation of lattice QCD is number of lattice points you can consider, going from 4D to 3D is actually a huge win.

[SOXBLOX]

On 4/13/2021 at 7:16 PM, K^2 said:

Current mass, also known as bare mass or...

Wow, I've never heard those terms before. Learn something new every day!