When I wrote my article last week about the relation between the Higgs and gravity, emphasizing that there really was no relation at all, I said that the Higgs field is not the universal giver of mass. I cited four reasons:
- The Higgs field does not give an atomic nucleus all of its mass, and since the nucleus is the vast majority of the mass of an atom, that means it does not provide all of the mass of ordinary matter.
- Black holes appear at the centers of galaxies, and they appear to be crucial to galaxy formation; but the Higgs field does not provide all of a black hole’s mass. In fact the Higgs field’s contribution to a black hole’s mass can even be zero, because black holes can in principle be formed from massless objects, such as photons.
- There is no reason to think that dark matter, which appears to make up the majority of the masses of galaxies and indeed of all matter in the universe, is made from particles that get all of their mass from the Higgs field.
- The Higgs field, though it provides the mass for all other known particles with masses, does not provide the Higgs particle with its mass.
Although it doesn’t matter too much to the main point of the Higgs-and-gravity article (since the first three points are not in question), the editor of a leading physics journal, Robert Garisto, took issue with the fourth point, arguing that I was making a statement that really wasn’t right, or at least is too strong. His argument has some merit, though in the end, I stick with my statement. I think it’s worth describing what he had in mind (as best I understand it) and why I feel strongly that one should think about it differently. There are some semantic aspects to the disagreement, but there are also some interesting and important subtle scientific points. I don’t want to suggest that this discussion is really that big a deal — the very fact that we can argue about whether the Higgs field does or doesn’t provide the Higgs particle with its mass distinguishes the Higgs particle from, say, the W particle, whose mass indisputably arises from the Higgs field. But there’s something to learn here about quantum field theory and how the Higgs mechanism works. Continue reading
With my series of articles on Fields and Particles complete, I’m continuing my series of articles on How the Higgs Field Works. (These sets of articles require a little math and physics background, the sort you’d get in your first few months of a beginning university or pre-university physics class.)
The first article in the new series was an overview of The Basic Idea behind how the Higgs field works. (In these articles I’m mainly concentrating on the simplest type of Higgs, the Standard Model Higgs field and particle.) Then came an article about why and how the Higgs field becomes non-zero. And the newest article explains how the Higgs particle arises as the quantum of waves that oscillate around the non-zero value of the Higgs field, and how its mass is determined by the equation of motion of the Higgs field.
One of the questions I get most often from my readers is this:
- Since gravity pulls on things proportional to their mass, and since the Higgs field is responsible for giving everything its mass, there obviously must be a deep connection between the Higgs and gravity… right?
It’s a very reasonable guess, but — it turns out to be completely wrong. The problem is that this statement combines a 17th century notion of gravity, long ago revised, with an overly simplified version of a late-20th century notion of where masses of various particles comes from. I’ve finally produced the Higgs FAQ version 2.0, intended for non-experts with little background in the subject, and as part of that, I’ve answered this question. But since the question is so common, I thought I’d also put the answer in a post of its own.
As preface, let me bring out my professorial training and correct the question above with a red pen:
- Since gravity pulls on things proportional to their
mass to a combination of their energy and momentum, and since the Higgs field is responsible of giving everything not everything, just the known elementary particles excepting the Higgs particle itself its mass, there obviously must be a deep connection between the Higgs and gravity… right? wrong.
Now let me explain these corrections one by one. Continue reading
[Long silence should be over for now; personal issues had to take precedence for a little while.]
Back to building up articles on how the Higgs field works! As part of the necessary background, I’ve added another general article on how particles and fields interact with each other to my series on Particles and Fields (with a little math — first-year university level.)
This one explains, among other things, how a small modification of the equations of motion for fields allows two particles of one type to annihilate and create a third one of a different type. Examples of such phenomena include the collision and annihilation of a quark and an antiquark to form a Z particle, or the collision and annihilation of two gluons to form a Higgs particle. Particle decay is often just the time-reversed process.
Moreover, similar modifications of the equations are essential in allowing the Higgs field to give mass to other particles.
So this is one of the most important articles, and one of the most sophisticated, to appear on this website so far. Although there are a couple of animations to help you visualize what is going on, to understand the text you will want to have read the other articles in the Particles and Fields series first.
Last week I finished up a set of articles explaining what Fields and “Particles” are. These articles require a small amount of math and physics, the sort you’d get in an advanced pre-university or a beginning university course.
[Articles with no technical requirements will come soon; in the meantime, try my widely read article on Why the Higgs Particle Matters.]
The Particles and Fields articles are a prerequisite to the next set of articles, which will explain what the (simplest type of) Higgs field is and how it does what it does. The first article, just completed, outlines the basic idea. Future articles to appear over coming days and weeks will fill in many details.
I have written a lot about energy, but I’ve put off introducing the most important type of energy again and again. It’s the most important, because it is this type of energy that is responsible for all the structure in the universe, from galaxy clusters down to protons and everything in between. It is the most challenging to write about because it is not particularly intuitive. All the types of energy we intuitively understand, such as the energy of motion, are positive, but this type of energy, crucially, can be negative. On this website I’ll call it “interaction energy” (not the technical term, but my own, chosen to avoid misconceptions that might otherwise arise) because it is associated with the interactions among fields — including their little ripples that we call “particles”. If you’ve taken physics you’ve heard of “potential” energy; what you learned within that concept is a subset of what is included under interaction energy.
I’ve been wanting to address this for a while, because many of you have asked penetrating and central questions about the basic structure of matter, such as:
- Why is the neutron stable inside of atomic nuclei, given that on its own it is unstable?
- Why is the proton arguably heavier than the quarks and gluons that make it up?
And there are other equally important questions that no readers have yet stumbled upon but that I ought to address. Before I can answer any of those questions, however, I have to first describe interaction energy and the role that it plays in structure.
So — without further ado, here’s the article. This was an especially hard article to write and it may well be confusing in places — so I very much welcome your feedback, in order that I can try to make it clearer, if necessary, in later versions.
[A Heads Up: I’m giving a public lecture about the LHC on Saturday, April 28th, 1 p.m. New York time/10 a.m. Pacific, through the MICA Popular Talks series, held online at the Large Auditorium on StellaNova, Second Life; should you miss it, both audio and slides will be posted for you to look at later.]
Is supersymmetry, as a symmetry that might explain some of the puzzling aspects of particle physics at the energy scales accessible to the Large Hadron Collider [LHC], ruled out yet? If the only thing you’re interested in is the answer to precisely that question, let me not waste your time: the answer is “not yet”. But a more interesting answer is that many simple variants of supersymmetry are either ruled out or near death.
Still, the problem with supersymmetry — and indeed with any really good idea, such as extra dimensions, or a composite Higgs particle — is that such a basic idea typically can be realized in many different ways. Pizza is a great idea too, but there are a million ways to make one, so you can’t conclude that nobody makes pizza in town just because you can’t smell tomatoes. Similarly, to rule out supersymmetry as an idea, you can’t be satisfied by ruling out the most popular forms of supersymmetry that theorists have invented; you have to rule out all its possible variants. This will take a while, probably a decade.
That said, many of the simplest and popular variants of supersymmetry no longer work very well or at all. This is because of two things: (click here to read the rest of the article.)
Posted in LHC Background Info, LHC News
Tagged atlas, cms, Higgs, LHC, mass, particle physics, searches, supersymmetry, top_quarks, virtual_particles
Ok, folks: yesterday’s first installment of my mass and energy article, discussing energy and momentum, has been extended with a second installment. Mass has made its appearance now, along with Einstein’s famous relations between energy, momentum, mass and speed, which are described and analyzed using… triangles. Yes, if you can remember what Pythagoras had to say about triangles, you can understand quite a lot about what Einstein was saying about relativity when he proposed his striking revision of Newtonian thinking. And I also address some obvious puzzles that bother everyone the first time they hear about this stuff…
The new material from today starts with the section marked “Mass … “.