particles

Why The Electron Can’t Have a Mass Without the Higgs Field

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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 … Read more

Theory Killers at the HCP conference

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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!

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Does the Higgs Field Give the Higgs Particle Its Mass, or Not?

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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:

  1. 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.
  2. 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.
  3. 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.
  4. 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.

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How the Higgs Field Does Its Thing

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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 … Read more

Two Major Steps Forward

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Apologies to those who’ve been asking questions: I’ve been away from the website for a few days (family matters) and have not been able to keep up with comments.  I will try to catch up over the coming day or two. But I do have two pieces of good news. First, I gave a public … Read more

After Springs, Waves

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On Monday I started a series of articles to explain particles and fields, aimed at those who’ve had a little bit of physics in their past (perhaps a semester or two just before or just at the beginning level at a university), and containing a very little amount of math. I first brought you the … Read more

A Little Math; A Lot of Physics

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One of my current goals is to explain how the Higgs field works to anyone who’s learned a bit of physics at the beginning-university or advanced pre-university level. As a step toward the goal, I am creating a set of pages that explain how fields work, why quantum mechanics implies that sufficiently simple fields have … Read more

CMS Finds a New (Expected, Composite) Particle

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Yes, it’s true what you’ve read; the CMS experiment at the Large Hadron Collider has found a new particle.  However, this isn’t one to get excited about.  Or rather, it’s the particle that’s excited, not the rest of us.  It’s a nice result; a neat result; but this particle is a slightly more massive version of a hadron that we already knew about, a composite object similar to a proton, built out of more fundamental particles we discovered over 30 years ago.  So in the grand scheme of things, this is minor news; no big mysteries to resolve here.  Nevertheless, congratulations to CMS! Finding such particles always involves reconstructing them from their decay products, and since this one decays in a very complicated way, the result represents a technical tour-de-force!

This is a similar story to one from last December, when ATLAS announced that it had found, with confidence, a new particle.  I explained to you then that there are particles and there are particles;

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