The part is greater than the sum of the whole?
March 10, 2012 5:14 AM   Subscribe

Scientists recently announced more evidence of the existence of the Higgs Boson, at a mass of around 125GeV. This indicates a mass significantly larger than that of a proton. If this is the particle that gives all other particles the property of mass, how is it possible for an single unit to have more mass than the particles it confers mass on?

I'm assuming this is some feature of quantum physics I haven't encountered. Down to the atomic level, it's pretty intuitive that the parts combine to make the whole (atom/molecule/cell etc.), and the whole is comprised of one or more parts (many protons, neutrons and electrons or in the case of these particles, various quarks and other less well known building blocks). However if this discovery turns out to be true, conventional logic would imply that a Higgs boson cannot be a component of an individual proton, and the property of mass must be transferred by some other means. How is this possible?

Please couch your answers in terms within reach of a bright college physics student, I haven't formally had physics classes beyond that level.
posted by fearnothing to Science & Nature (9 answers total) 9 users marked this as a favorite
Best answer: A boson (like the Higgs boson, or a photon, or a gluon) is just a perturbation or a wave in a field. They're usually predicted to be massless. However if one field couples with another field, like the higgs does, it can drag on the waves passing through them, which is basically where inertia (and mass) comes from. The higgs field does this. The thing about the higgs field is that it actually couples with itself, which causes bosons in the higgs field to also have inertia (and thus mass).

Higgs bosons aren't part of other particles, though. Think of them as being like a giant ball pit that the other particles swim through.
posted by empath at 5:24 AM on March 10, 2012 [9 favorites]

Response by poster: Well, that was a lot easier to grasp than I expected. I thought I'd have to get my maths head on!
posted by fearnothing at 5:32 AM on March 10, 2012

At the quantum level, it is possible to violate conservation of energy, for short periods. A particle can temporarily borrow energy (from no where) and give it back again afterwards. It's legal as long as the quantity of energy borrowed, multiplied by the duration of the loan, is less than Planck's constant.

Particles that mediate force are examples of this. An electric field is composed of "virtual photons", which are photons which come into existence in this way. "Charge" turns out to be the property of being able to create virtual photons.

In the current unified field theory, if a force mediating particle is massless then that force has infinite range, and that is the case for the electric force. But if the mediating particle has mass, then the range of that force is limited. The more mass the particle has, the shorter the range. That's because it cannot travel faster than light, so it can't affect something that is farther away than it could reach at just shy of the speed of light. Since Planck's constant is a really teeny tiny number, it's quite a severe limitation.

Since gluons have quite a lot of mass, the range of the strong force is very short, on the order of a couple of proton diameters. The weak vector boson is also quite massive, so the weak force has a very short range.

The significance of a high mass for the Higgs Boson should be that its range of activity should be even shorter, because its existence will be very, very brief.
posted by Chocolate Pickle at 8:55 AM on March 10, 2012

By the way, I'm not sure but I think that the theorists predicted the expected mass based on their expectations of range of effect.
posted by Chocolate Pickle at 8:56 AM on March 10, 2012

In the case of the proton, 99% of the mass is actually due to the potential energy in the quark-gluon field, not due to the Higgs.
posted by atrazine at 8:56 AM on March 10, 2012

Atrazine, yes, but why is energy treated as mass? That's what the Higgs field supposedly does.
posted by Chocolate Pickle at 9:02 AM on March 10, 2012

Mass is just energy that lives within fields that couple with the higgs field. Fields that don't couple with the higgs (the electromagnetic) are massless.
posted by empath at 9:34 AM on March 10, 2012

In the case of the proton, 99% of the mass is actually due to the potential energy in the quark-gluon field, not due to the Higgs.

Well, the mass isn't from that, but the inertia is from the higgs, yeah?
posted by empath at 9:35 AM on March 10, 2012

Just in passing: The W bosons have a mass of 80.4 GeV/c and the Z boson has a mass of 91.2 GeV/c. Those are the bosons which mediate the weak force, which is what controls neutron decay (among other things).

The Neutron has a mass of 0.94 GeV/c, so the Z boson is almost a hundred times more massive than the neutron.
posted by Chocolate Pickle at 11:46 AM on March 10, 2012

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