Over the past week or so, there has been unnecessary confusion created about whether or not there’s some relationship between (a) the Higgs particle, recently discovered at the Large Hadron Collider, and (b) the Big Bang, perhaps specifically having to do with the period of “Cosmic Inflation” which is believed by many scientists to explain why the universe is so uniform, relatively speaking. This blurring of the lines between logically separate subjects — let’s call it “Cosmic Conflation” — makes it harder for the public to understand the science, and I don’t think it serves society well.
For the current round of confusion, we may thank professor Michio Kaku, and before him professor Leon Lederman (who may or may not have invented the term “God Particle” but blames it on his publisher), helpfully carried into the wider world by various reporters, as Sean Carroll observed here.
[Aside: in this post I'll be writing about the Higgs field and the Higgs particle. To learn about the relationship between the field and the particle, you can click here, here, here, or here (listed from shortest to most detailed).]
Let’s start with the bottom line. At the present time, there is no established connection, direct or indirect, between (a) the Higgs field and its particle, on the one hand, and (b) cosmic inflation and the Big Bang on the other hand. Period. Any such connection is highly speculative — not crazy to think about, but without current support from data. Yes, the Higgs field, responsible for the mass of many elementary particles, and without which you and I wouldn’t be here, is a spin-zero field (which means the Higgs particle has zero spin). And yes, the “inflaton field” (the name given to the hypothetical field that, by giving the universe a lot of extra “dark energy” in the early universe, is supposed to have caused the universe to expand at a spectacular rate) is also probably a spin-zero field (in which case the inflaton particle also has zero spin). Well, fish and whales both have tails, and both swim in the sea; yet that doesn’t make them closely related. Continue reading
I’ve been quite busy with some physics research this week, but I have nevertheless managed to finish a new article on electrons, part of my Structure of Matter series, which aims (among other things) to introduce a non-expert to particle physics, step-by-step. The completion of this article feels like a significant step for this website. After all, the electron was the first subatomic particle and the first of the apparently-elementary particles to be discovered, about 115 years ago, and its discovery really gave birth to the field of particle physics we know today. Moreover, it was the failure to describe the behavior of electrons within and outside of atoms that forced physicists to go beyond Newtonian views of physics processes, and introduce the theory of quantum mechanics. Electrons, tiny as they are, are enormous in human life; they play a key role in all chemical reactions, including those that sustain our bodies. Beyond that, they lie at the heart of much modern technology — electronics! And there’s more. So no particle physics website can be complete without an electron webpage.
Looking ahead, a question I sometimes get asked is whether I’m sure electrons (or any other elementary particles that physicists talk about) really exist. After all, it is true I’ve never seen a picture of one taken with any sort of microscope! Well, in answer to this question, I want to write an article on why we particle physicists are so confident that electrons (and atomic nuclei) exist… explaining the types of experiments and the types of logical reasoning that lead to this conclusion. I suspect a lot of readers will find such an article interesting; after all, why should one take expert knowledge for granted just because it appears in a textbook or on a website? Readers should demand to know where the knowledge came from — and a writer should be prepared to answer.
My rather hasty, breathless and inconsistent summaries (#1, #2 and #3) of last week’s talks at the excellent Higgs Symposium (held at the University of Edinburgh, as part of the new Higgs Center for Theoretical Physics) clearly had their limitations. So I thought it might be useful to give a more organized overview, with more careful language appropriate for non-expert readers, of our current knowledge and ignorance concerning the recently discovered Higgs-like particle (which most of us do believe is a Higgs particle of some type, though not necessarily of the simplest, “Standard Model” type.)
I’m therefore writing an article that tries to put the questions about the Higgs-like particle into a sensible order, and then draws upon the talks that were given at the Symposium to provide the current best answers. About half of the article is done, and you’re welcome to read it. Due to other commitments, I won’t probably get back to finish it until next week. But “Part 1″ is long enough that it will take some time for most readers to absorb anyway…
After a hiatus for a hurricane and a trip to a conference in Asia, I am adding one more article to my series on How the Higgs Field Works, following my series of articles on Fields and Particles. (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. I’m still thinking about how to structure a similar set of articles that require no math or physics; that’s much harder, of course!)
The first article in the series explained the basic Idea behind how the Higgs field works. Then came an article about why and how the Higgs field becomes non-zero, and a third concerning how the Higgs particle arises as the quantum of waves that oscillate around the non-zero value of the Higgs field. The new article tries to clarify why there’s no alternative to introducing a Higgs field, explaining that it’s otherwise impossible to reconcile two apparently contradictory features of our world: a mass for the electron (and many other types of known particles) and the properties of the weak nuclear force.
This article contains the most elaborate equations and concepts that I’ve had to introduce to my readers, so it won’t be suitable for everyone (though it still only requires some first-year physics/math.) But on the other hand, it seems necessary for me to write it, since it’s the only place that I’ve explained not only why the Higgs field can give mass to the known particles, but why it (or something very much like it) must do so.
(Note that in these articles I’m mainly concentrating on the simplest type of Higgs, the Standard Model Higgs field and particle. However, most of the basic concepts in these articles apply even for more complicated cases.)
There were many interesting results presented yesterday at the HCP conference in Kyoto, and they were both too numerous and too detailed for me to completely absorb as yet — a follow-up will clearly be needed. But a few are obviously so important that I want to point them out now.
First, both ATLAS and CMS, the two general purpose experiments at the Large Hadron Collider [LHC], produced important new results on “multileptons”. Based on a significant fraction of their 2012 data, they looked for signs of new phenomena that would appear as proton-proton collisions that produce at least three leptons or anti-leptons, or even (in unusual combinations and/or along with other unusual things) two leptons or anti-leptons. (I’ll just summarize this class of studies as “multileptons” for the purpose of this brief post and be more specific at a later date.) ATLAS used about 50% more data than CMS, but CMS had a more intricate analysis of their data, so I believe the results were similar where they can be compared. [By the way, the CMS result was approved to be shown at this conference under extreme conditions; at least two of the major players in the analysis had no power or internet for over a week following Hurricane Sandy!]
The bottom line is simple: neither CMS nor ATLAS sees any significant deviation from what is predicted by the Standard Model. And this now kills off another bunch of variants of many different speculative ideas. The details are extremely complicated to describe, but essentially, what’s dead is any theory variant that leads to many proton-proton collisions containing
- two or more top quark/anti-quark pairs
- multiple W and Z particles
- two or more as-yet unknown moderately heavy particles that often decay to muons, electrons and/or their anti-particles
- new moderately heavy particles that decay to many tau leptons
and probably a few others I’m forgetting. While multilepton searches (especially those for 3 or more leptons) are often touted as a great way to look for supersymmetry in particular, that description vastly understates their power — they are a great way to look for many different types of phenomena not predicted in the Standard Model. (This is something that a number of scientists at Rutgers University have been emphasizing in talks and papers.) And both experiments have demonstrated this with various interpretations of their results; CMS has over a dozen of them! Continue reading
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