Where’s the “like” button on this here Interweb?
You could have masses (and thus gravity) without the Higgs; you just wouldn’t have the same set of masses. As for “gravity without mass”, well, that depends on just precisely how you define “mass”. Gravity is actually caused by a more complicated thing called stress-energy; mass just corresponds to one of the 16 (or 10, depending on how you look at it) components of that (it’s just that, in typical experience, it’s by far the largest component).
I’ll probably get shot down for this, but couldn’t gravity be regarded as the absence of some force rather the presence of such a force (i.e. gravity).
Since the universe is occupied by a seething soup of virtual particles flashing in and out of existence and since we know this phenomenon generates pressure (Casimir effect?), if congregations of mass displace this pressure to some degree, couldn’t gravity result from the displacement.
I’m sure I’m missing something obvious, so be gentle.
Chessic, to give a simplified answer, there is a distinction between gravitational mass and inertial mass. Chronos is correct in saying that the source of the gravitational field is a complex entity properly known as “stress-energy”, but for the purposes of this discussion let’s consider a universe empty save for a single elementary particle. Now the only source of the gravitational field is this particle’s mass and energy. Which mass is it? It’s the gravitational mass, such as might appear in Newton’s law of gravity, F = GM1M2/r^2.
The Higgs boson is a theoretical mechanism to explain the existence of inertial mass, which is a subtly different concept. Inertial mass is defined by the ratio of an applied force to the resulting acceleration: m = F/a. Now, in a simplified situation such as this, where there’s none of that General Relativity business complicating things, we find that the gravitational mass has the same value as the inertial mass. This makes intuitive sense, but no one has a valid deeper reason as to why (as far as I know).
Such models have been proposed, and qualitatively, they actually end up looking almost exactly like gravity (Newtonian gravity, at least). There’s some subtle point on which they fail, but I can’t off the top of my head remember what it was, though.
General Relativity explicitly assumes that gravitational mass equals inertial mass. That is the principle of equivalence, after all.
The best heuristic for how the Higgs boson gives mass to, say an electron, that I have read was to view the electron as plowing through the Higgs bosons, leading to inertia.
Yes, you’re right. I think I got carried away with making sure there was none of the recent confusion about the mass of an object versus the mass of a system.
Like.
I thought about posting something simalir (re general relatvity ‘explaining’ the connection between inertial and gravitational mass), but I’d sound a note of caution because there’s issues that aren’t always immediately apparent.
General relativty ties very neatly why the inertial force felt by an object (of negligible size) as it undergoes acceleration and the graviational force felt by the same object as it held ‘stationary’ in a gravitational field are both proportional to the same parameter of that object: ‘m’ (i.e. mass). This can be explained in terms of the Christoffel symbols.
However there isn’t really a simple way to connect the active gravitational mass of an object and it’s inertial mass in general relativity (not saying it’simpossible but the most straightforward way to go about it would be to derive the Newtonian limit, which isn’t very enlightening other than perhaps to show why Eisntein choose the particualr form and constants of proportionality for his field equations).
Ok, this is getting a lot closer to providing an answer for the this part of the OP
So the Higgs-Boson is involved with creating inertial mass in other particles. It seems to do this through ‘coupling’ which affects other particles, but it doesn’t sound like absorption by other particles So does an HB affect lots of other particles that it encounters, or does it get ‘consumed’ in the process somehow? If it it is not somehow converted into something else, and it is a necessary part of the explanation of inertial mass, why haven’t we found one? Shouldn’t they be all over the place?
How many of these Higgs Boson things are there? One, two, an unimaginable number?
If all other particles get their mass from the interaction with an HB field, that field must be everywhere and constant otherwise particle masses will inconstant… and nobody is predicting that, or are they?
And particle-particle (wave-wave) interactions usually observe the inverse square law, or at least some distance limiting effect (the weak and strong forces may not be inverse square (can’t remember) but still are weaker at a distance)… is the HB field the same… doesn’t seem like it could.
That’s what I’ve been wondering. If they’re huge and everywhere, why can’t we detect them by now?
I have merged two separate threads concerning the Higgs Boson (the OPs are posts #1 and #4), and edited the title. My apologies for any disruption in the space-time continuum. 
Colibri
General Questions Moderator
It is my understanding that, in particle physics terms, “mass” is usually given in units of the energy required to create a free-standing instance of the particle in question. For example, the electron has a “mass” of 0.511 MeV. In order to detect a free Higgs particle, enough energy must be supplied to provide the “mass” of the Higgs Boson.
As of 2006, measurements of electroweak observables allowed the exclusion of a Standard Model Higgs boson having a mass greater than 285 GeV at 95% CL (confidence level), and estimated its mass to be 129 (+74/−49) GeV (the central value corresponds to approximately 138 proton masses)
In highly-energetic collisions, many traces are found in the results, and must be sifted carefully to determine if any tracks correlate with the theoretical Higgs particle. The fact that they are “huge”, ironically, makes it harder to detect them, not easier.
Ok, now I see a variety of sources that say that the HB is difficult to detect because of it’s short life. That only raises more questions. Do the HBs confer inertial mass in other particles and then decay? Is there an ongoing process of these particles being created and destroyed? And if so, where does the energy come from to create them?
Apparently the HB creates a Higgs Field. Have we detected the field? Is the particle merely an explanation for the existence of the field?
This sounds like a long stack of turtles.
Here—Sheldon will diagram it all out for you.
It’s not all that turtle-y. But, there is a potentially confusing jumble of information in the thread so far (some excellent info, some close-but-not-quite info, and some doozies.)
The bare Standard Model has only massless particles. However, we observe particles with mass. This shortcoming of the model can be remedied in a very clean way by introducing a new particle, the Higgs. Sort of.
What is actually introduced (in the minimal Standard Model, at least) is the Higgs field doublet. (A “field” is the mathematical entity that underlies the Standard Model’s description of all stuff. These fields are more complex than, say, an electric field, but you can think of them as similarly space-filling and having interaction dynamics. A physical particle is a quantum excitation of the corresponding field. As for “doublet”: one actually introduces a pair of Higgs fields that are closely related to one another and to the underlying form of the electroweak interaction, but this is a technicality for this post. Only a single physical Higgs particle (i.e., possible field excitation) exists after the machinations below.)
The Higgs field doublet is introduced with a particular form of self-interaction such that it is energetically favorable for the field to have a non-zero value rather than a zero value. Thus, if you look at the vacuum of space and ask “What is the value of the Higgs field here?” you’ll find a constant, non-zero answer. This doesn’t mean that there are Higgs particles out in empty space. Higgs particles would be excitations of the field, and those cost energy. (“Field” does not equal “particle”. “Excitation” equals “particle”.)
The fact that the universe prefers to keep some finite “Higgs-ness” everywhere has two major implications. The first relates to the gauge bosons (force carriers) of the electroweak interaction. These bosons are introduced into the Standard Model as massless particles (necessarily). However, the theory so created is untenable, as its fields are not all in their lowest energy state thanks to the Higgs doublet’s peculiar self-interaction. With a little bit of mathematical rearrangement, however, you can re-label what you call the physical fields and, in the process, put everything into the ground state. Assuming that nature will, indeed, seek out this ground state, then the newly cast boson fields must be the real physical ones. And indeed, this process of “electroweak symmetry breaking” (i.e., this rearrangement of field definitions) predicts one massless gauge boson (the photon) and three massive gauge bosons (Z[sup]0[/sup], W[sup]+[/sup], W[sup]-[/sup]). What’s more, the predicted masses of the W and Z bosons are related, and measurements of the relation between them is predicted to change in a very strict way as a function of the energy scale at which the measurement is taken. These predictions agree beautifully with observations, and this is one of several reasons why the Higgs “ought to” be there. (That is, the formalism is both elegant and complex, yet it seems to just plain work.)
Electroweak symmetry breaking via the Higgs mechanism also provides a convenient way to give the fermions (e.g., electrons, quarks, …) mass. One can introduce interactions between the bare, massless fermion fields and the Higgs field. Then, when the symmetry of the model is broken and the Higgs field acquires a non-zero value everywhere (its so-called “vacuum expectation value”), the fermions all find themselves interacting with this ubiquitous Higgs field. Remember: the Higgs field itself may be non-zero, but it is still in the lowest energy state, so there’s no free energy to steal. There’s also no way to detect that it’s there… except in two ways: (1) see if any fermions are coupling to it, which is equivalent to looking to see if any fermions have mass. [Check!]. Or, more convincingly: (2) excite the field (which means: create a Higgs particle).
To create a Higgs particle, you must expend enough energy to create its mass. The Large Hadron Collider is certain to have enough energy in its proton-proton collisions to create a Higgs, if it exists. This is why it has gone undetected: its hard to create. Someone mentioned that its short lifetime is the issue. On the contrary – its short lifetime simply guarantees that it will decay quickly into daughter particles that can be detected. (The detection process itself is non-trivial, too, but that would deserve a thread, or at least post, of its own, so I’ll leave it be for now.)
There could be multiple Higgs particles. For instance, in the minimal supersymmetric extension to the Standard Model (proposed to solve a very serious fine-tuning problem that I’ve skipped over), one ends up with five physical Higgs particles (three neutral, two charged).
It is possible that neutrinos (which are fermions) do not gain their mass via a Higgs coupling. Because they are electrically neutral, one can introduce them into the model in a different way (as “Majorana” particles instead of “Dirac” particles, FWIW), and this allows one to write mass terms into the equations without reference to the Higgs’s vacuum expectation value. It is not known if neutrinos are Majorana particles, but it is an active area of research.
Regarding inertial mass… The word “inertia” really shouldn’t show up anywhere here. As was pointed out by MikeS, the proton (for example) has plenty of inertial mass, and this mass has little to do with the Higgs boson and everything to do with the fact that it’s a macroscopic, bound system. And, as the neutrino example shows, even assumed fundamental particles can have mass without coupling to the Higgs.
Hey, thanks everybody for your patient explanations; I had to work late, and am just getting back.
—But now I’m really confused. As I understand it,
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the Higgs Boson is a theoretical particle they are hoping to find in the quantum debris from the collision of protons
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therefore, the Higgs Boson is theoretically ***part ***of a whole proton
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[Hi, Opal!] Chronos has just said above that the mass of the Higgs Boson, part of a proton, is something in the ballpark of a few thousand times the mass of a proton. I know that mass is not size, nor weight; but how can this be?
Personally, I have come to believe pretty much the same thing dzero said. But that’s about gravity.
I suspect that CP Violation is involved here somehow, if only by analogy.
There’s your problem. A particle collider isn’t like a hammer that we use to smash open protons and look at what’s inside. Rather, when we smash very high-energy particles together, some of this energy is turned into particles — don’t forget that energy and mass can be traded for each other at the exchange rate of E = mc[sup]2[/sup]. If you could look inside a proton at any given moment, it’s exceedingly unlikely that you’d actually see a Higgs boson in there.
I’ve been wondering about this recently. My understanding was that the mass of a nucleus is slightly less than that of its constituent protons and neutrons, the “mass defect” corresponding to the binding energy. So it surprised me to learn that the mass of a proton is larger than that of its constituents due to interactions (which presumably bind the quarks to each other).