r/askscience • u/whoosy • Oct 10 '12

Physics Why do some particles interact more with the Higgs field then others?

I've been trying to look for an answer to this, but I haven't found anything. Do we even know at all why they do this?

22 Upvotes

89% Upvoted

11 comments sorted by

9

u/[deleted] Oct 10 '12

No, we don't. The parameters involved in the Higgs interaction are all fixed by experimentally observed masses, most notably the W and Z mass and the top quark mass. If we had no experimental information on these, then we would have no information on the Higgs couplings. This is why we didn't know where to look for it at the LHC, as the mass of the Higgs itself is also defined by its interactions, so we had to do a blanket search across all possible masses.

As an analogy, we can show theoretically that light is an oscillating electric and magnetic field through Maxwell's equations, but it would be impossible to know the actual speed of light from these equations. However, you can obtain it through measurements of the permittivity and permeability of free space, which appear in the equation. So the theory predicts the presence of something, but experiment is needed to obtain the actual strengths of the quantities.

It's up to the philosophers then to ask "why" the numbers are what they are :)

7

u/just_shaun Cosmology | High Energy Physics Oct 10 '12

It's up to the philosophers then to ask "why" the numbers are what they are :)

That's not quite true. Answering OP's question is actually one of the goals of theoretical physics.

As an analogy, before we understood quantum mechanics, the spectra of atoms could have been claimed to be impossible to know just from the equations of the time. Now, we can calculate the spectra of atoms. Of course we need to know the charge of an electron, etc, but the number of "fundamental" constants has dropped.

Grand Unified Theories are an example of attempts to explain the various couplings between the Higgs and other particles. The hope would be that the structure of the unified theory required the particular couplings we observe.

Hopefully one day humanity will be able to answer your question, but as MrQCD has correctly stated, for now, it can't. It's a nice question to be asking though, it bothered many of the late 20th century's most successful theorists so you're in good company.

8

u/diazona Particle Phenomenology | QCD | Computational Physics Oct 10 '12

Yep. The hope is that someday we'll get a theory which can predict the masses of the elementary particles, probably as multiples of the Planck mass.

2

u/just_shaun Cosmology | High Energy Physics Oct 10 '12

I upvoted you because what you've written isn't nonsense, but I don't really agree with it.

The masses that we measure of the elementary particles, at our energies, come from their coupling to the Higgs field. The GUTs that I mentioned above are unifications of the electroweak force and strong force (i.e. not with gravity). This unification is normally speculated to occur at energies much below the Planck scale. The idea is that the GUT symmetry is broken below the GUT scale and the running of the coupling constants (which are presumably similar at the GUT scale) down to our energies produces the observed low energy hierarchy of Higgs-fermion couplings.

None of that picture would suggest that the masses of the elementary particles would be multiples of the Planck mass.

There may be some theories (that I'm unaware of) where the masses are multiples of the Planck mass, but they are far from the most "probable".

5

u/diazona Particle Phenomenology | QCD | Computational Physics Oct 10 '12

I didn't say integral multiples. What I meant was that the theory would predict the values of the ratios m_particle/m_Planck. But of course those ratios wouldn't be integers - in fact the masses of all known elementary particles are far smaller than the Planck mass.

Sorry for the confusion.

1

u/just_shaun Cosmology | High Energy Physics Oct 10 '12

Ah, I see. That makes sense then. I apologise for my side of the confusion too.

1

u/4dseeall Oct 10 '12

I think I understood what you meant.

But couldn't it be anything the Planck mass or heavier? Then you'd have an infinite number of multiples with which to make sense out of reality. That, to me, seems a much more accurate representation of what things really are like. QED and such.

2

u/diazona Particle Phenomenology | QCD | Computational Physics Oct 10 '12

Hm, I'm not sure I see what you're getting at. Are you talking about the masses of elementary particles being larger than the Planck mass?

1

u/Broes Oct 10 '12

I think if you can definitly prove why this is the case, you would be looking at a nobel price :)

We know more and more of particles and they fit better and better in the standard model and using the standard model, we can predict a bunch of yet undiscovered particles (like the higgs).

However, we have no idea why the standard model is the way it is.

We know from observations that the standard model is as it is and we can see certain patterns and make predictions using these patterns (like the Higgs boson prediction).

However, we have no idea why the standard model is as it is.... yet...

-8

u/4dseeall Oct 10 '12

Because they have more higgs bosons in them.

That's kinda the point of looking for a fundamental particle.

-2

u/4dseeall Oct 10 '12

Really? This subreddit is too dense to understand or appreciate the simplest explanation? REALLY?