Particle size and mass

[Ranku]

Are there examples of particles with same size but different masses?

 

[malawi_glenn]

Elementary particles do not have a spatial extension in QFT. Size of a hadron one usually mean rms charged radius which in some way is analogous to how we can talk about "size" of an atom.

I think you either need to specify what you mean by size, or simply re-evaluate your concept of size in subatomic physics.

 

[Ranku]

Elementary particles do not have a spatial extension in QFT. Size of a hadron one usually mean rms charged radius which in some way is analogous to how we can talk about "size" of an atom.

I think you either need to specify what you mean by size, or simply re-evaluate your concept of size in subatomic physics.

It can be rms radius charge or cross section. So are there examples of particles with similar ‘size’ but different masses?

 

[malawi_glenn]

It can be rms radius charge or cross section. So are there examples of particles with similar ‘size’ but different masses?

Cross section means reaction probability in particle physics :)
Hadrons don't have a definitive size and only a few charged rms values are known experimentally. Some have been calculated theoretically. But sure for instance the proton and the neutron have both similar size and mass. Kinda depends on what you mean by similar size, what does similar mean? Plus/minus 10%? There are no particles that have exactly the same mass except particle/anti particle pairs.

 

[Vanadium 50]

Plus/minus 10% there are no particles that have exactly the same mass except particle/anti particle pairs.

Sure about that?
I won't cheat by using isospin multiplets.
I won't cheat by using SU(3) flavor multiplets.
I won't cheat by using quarkonia.
I won't cheat by picking particles with identical quark content.
I won't even cheat by picking particles with identical valence quark content.

Λ(1115) and φ(1020), 9.3% different.

 

[malawi_glenn]

Sure about that?

I forgot a "?" there, and a capital letter :) I was typing on my cell phone.
That sentence makes no sense as you quoted it, since plus/minus 10% and exactly the same does not fit xD

Now it should make more sense:

Plus/minus 10%? There are no particles that have exactly the same mass except particle/anti particle pairs.

So the "plus/minus 10%?" I mean't how accurate the OP wanted "similar" to be.

 

[mfb]

There is no good way to measure this but D and B mesons should have a similar size, for the strong interaction both charm and bottom are simply a heavy quark. They have very different masses.

 

[malawi_glenn]

There was a recent thread with a similar question here https://www.physicsforums.com/threads/would-higher-mass-quarks-result-in-smaller-baryons.1017161/
Check out those replies and references therein.


https://arxiv.org/abs/1810.09040 (very crude model though)
D-meson (rms) charged radius 0.41 fm
B-meson (rms) charged radius 0.35 fm
about 15% difference.

Now D-meson mass is about 1.9 GeV/c² and B-meson mass is about 5.3 GeV/c² almost a factor 3 heavier :-)

 

[Vanadium 50]

There is no good way to measure this

Transition magnetic moments tells you this. The problem is that these are OK for B*'s but small for D*'s.

 

[malawi_glenn]

Perhaps this article is relevant for the thread https://arstechnica.com/science/202...is-apparently-shorter-than-its-charge-radius/

 

[malawi_glenn]

So if mass size and charge size and scalar size are all different, a proton can't be a point particle.

No one has ever said that protons are point particles either. At least not here. And if they do, they are of course wrong. The proton is not an elementary particle. Did you think it is or what? Even if those radii were the same, proton would not be a pointparticle.

Here is the paper in Nature https://www.nature.com/articles/s41586-023-05730-4 which is a pretty good source.

 

[apostolosdt]

[...] Now, go and find for us the proof of neutrino size. Are you working on it?

These last posts remind me of the opening paragraph in Laughlin's Nobel Lecture.

 

[malawi_glenn]

These last posts remind me of the opening paragraph in Laughlin's Nobel Lecture.

By all means, enlighten us.

 

[apostolosdt]

By all means, enlighten us.

Though not difficult to trace that Lecture, what I recalled was this (in Laughlin's own words):

(https://www.nobelprize.org/uploads/2018/06/laughlin-lecture.pdf).

 

[vanhees71]

The correct link is

https://www.nobelprize.org/uploads/2018/06/laughlin-lecture.pdf

 

[malawi_glenn]

Did StandardsGuy dissapear? If some moderation has been done, perhaps some more posts should be removed?

 

[apostolosdt]

The correct link is
https://www.nobelprize.org/uploads/2018/06/laughlin-lecture.pdf

Thanks a lot for the correction. Appreciated.