# How does the Higgs field differentiate between particles giving specific masses

1. Jul 12, 2012

### Phyzwizz

I was wondering how (or if it is known) the Higgs assigns different masses to different particles. We know that mass comes from the resistance that the Higgs field provides to particles but why are some particles such as photons able to move through without a hint of resistance, whereas particles such as the top quark go through the field like it. Is it just the simple fact that top quarks are larger than photons and have a higher probability of colliding with the Higgs bosons that make up the Higgs field or is it something more deep and more exact than this?

2. Jul 13, 2012

### tom.stoer

The "resistance" is a nice picture but partially misleading; e.g. there is no deceleration of particles due to the Higgs field.

The mass generation is due to a) the vacuum value of the Higgs field and b) a specific coupling of the particles with this field; whereas a) is universal, b) is constructed such that each known fermions gets its specific mass via its specific Yukawa coupling between the fermion (electron, myon, tyu, quarks flavor) and the Higgs field.

Refer to the last formula in http://en.wikipedia.org/wiki/Electroweak_interaction where f is the index for different fermions species.

3. Jul 16, 2012

### Doofy

This will no doubt have been asked before as it seems like an obvious question to me, but you know how you say each particle gets a specific mass due to having a specific coupling - hasn't the problem just been deferred from wondering how a particle gets its mass to wondering how it gets its coupling?

I mean, are the values of the coupling constants (and hence each particle's mass) theoretically predictable, or are they just put in "by hand" in the same way that particles previously "just had" a certain mass?

4. Jul 16, 2012

### tom.stoer

Yes.

No.

Yes and no; due to the chiral structure of the weak gauge theory the usual Dirac masses are not appropriate; therefore one needs a new mechanism for fermion mass generation

Last edited: Jul 16, 2012
5. Jul 20, 2012

### Mononoke

Hi,

I had the exact same question as the OP. Thanks for the clear response. Can you please explain the quoted part a little further. I want to know if the higgs mechanism can generate masses of fundamental particles from first principles

6. Jul 20, 2012

### w4k4b4lool4

The honest answer, if I may, is that nobody knows why the Standard Model couplings have the value they do ...
As far as I understand, they are just measured experimentally, with no (or little) theoretical motivation for their specific values.
The hope is that there is some underlying theory that will explain the value of all the couplings.
This is, after all, one of the main motivations for looking beyond the Standard Model ...

7. Jul 20, 2012

### dipstik

so typically the ground state of a particular field will be operated on by creation operator to generate a particle. well, the higgs field is operated on to create he higgs boson, but are there mass creation operators, or is it only the yakawa coupling that determines the mass?

what i would like to see is some way of quantizing the lagrangian density given by general relativity to give us some kind of coupling to the higgs lagrangian density, without having to deal with the coupling at all.

I found this from 1991: Higgs Field and a New Scalar-Tensor Theory
of Gravity nternational journal of theoretical physics [0020-7748] Dehnen, H yr:1992 vol:31 iss:1 pg:109

8. Jul 20, 2012

### tom.stoer

I don't know what "mass creation operators" should be; but yes, it's only "vev * Yukawa coupling"

It's standard

Quantizing the SM Lagrangian on a curved background geometry is difficult and will not give us any new insights.
Quantizing GR is the quantum gravity problem which is beyond the scope of the SM and all these discussions regarding the Higgs.