Higgs

The Topic(s) of the Upcoming Book

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Every book on science focuses attention on a little sliver of a vast, complex universe. In Waves in an Impossible Sea, I had intended to write mainly about the Higgs field, and the associated Higgs particle that was discovered in 2012 to great fanfare. I was planning to explain how the Higgs field does its job in the universe, and why it’s so important for the existence of life.

However, this plan had a problem. The Higgs field would be irrelevant were it not for quantum physics on the one hand and Einstein’s relativity on the other, and to comprehend the latter requires some understanding of Galileo’s earlier concept of relativity. To show why the Higgs field can give mass (more precisely, rest mass) to certain types of particles requires combining all of these notions together. Each of these topics is daunting, worthy of multiple books, and I knew I couldn’t hope to cover them all in 100,000 words!

To my surprise, resolving this problem wasn’t as difficult as I expected, once I picked out a few crucial elements about each of these subjects that I felt everyone ought to know. Lining up those conceptual points carefully, I found I could give a non-technical yet accurate explanation of how elementary particles can get mass from a Higgs field. (A more mathematical explanation has been given previously on this website, in two series of articles here and here.)

Yet what surprised me even more was that the book’s main subject slowly changed as I wrote it. It became focused on the question of how ordinary life emerges from an extraordinary cosmos. Though a substantial section of the book is devoted to the Higgs field, it is situated in a much wider context than I originally imagined.

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The Standard Model More Deeply: The Nature of Neutrinos

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Earlier this week I explained how neutrinos can get their mass within the Standard Model of particle physics, either by engaging with the Higgs field once, the way the other particles do, or by engaging with it twice. In the first case, the neutrinos would be “Dirac fermions”, just like electrons and quarks. In the second, they’d be “Majorana fermions”. Decades ago, in the original Standard Model, neutrinos were thought not to have any mass at all, and were “Weyl fermions.” Although I explained in my last post what these three types of fermions are, today I want go a little deeper, and provide you with a diagrammatic way of understanding the differences among them, as well as a more complete view of the workings of the “see-saw mechanism”, which may well be the cause of the neutrinos’ exceptionally small masses.

[N.B. On this website, mass means “rest mass” except when otherwise indicated.]

The Three Types of Fermions

What’s a fermion? All particles in our world are either fermions or bosons. Bosons are highly social and are happy to all do the same thing, as when huge numbers of photons are all locked in synch to make a laser. Fermions are loners; they refuse to do the same thing, and the “Pauli exclusion principle” that plays a huge role in atomic physics, creating the famous shell structure of atoms, arises from the fact that electrons are fermions. The Standard Model fermions and their masses are shown below.

Figure 1: The masses of the known elementary particles, showing how neutrino masses are much smaller and much more uncertain than those of all the other particles with mass. The horizontal grey bar shows the maximum masses from cosmic measurements; the vertical grey bars give an idea of where the masses might lie based on current knowledge, indicating the still very substantial uncertainty.

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The Standard Model More Deeply: Masses, Lifetimes and Forces

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Today’s post is for readers with a little science/math background:

Last week, I explained, without technicalities, how the various elementary forces of nature can be inferred from the pattern of lifetimes of the known particles.  I did this using an image, repeated below, that organized the particles by their masses and lifetimes.  I’ll add more non-technical posts on the Standard Model in the coming days. But today’s post is a tad more technical, using dimensional analysis (a physicist’s secret weapon) (which I demonstrated here, here and here) to explain key features of the image: the red line, the blue line, and the particles at the upper left, as well as why there is a high-energy and a low-energy version of the weak nuclear force.

Figure 1:  An assortment of the known particles particles clustered into classes according to the “force” that causes them to decay. See this recent post for details.

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Celebrating the 34th Birthday of the Higgs Boson!

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Ten years ago today, the discovery of the type of particle known as the “Higgs Boson” was announced. [What is this particle and why was its discovery important? Here’s the most recent Higgs FAQ, slightly updated, and a literary article aimed at all audiences high-school and up, which has been widely read.]

But the particle was first produced by human beings in 1988 or 1989, as long as 34 years ago! Why did it take physicists until 2012 to discover that it exists? That’s a big question with big implications.

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5th Webpage on the Triplet Model is Up

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Advanced particle physics today: Another page completed on the explanation of the “triplet model,”  (a classic and simple variation on the Standard Model of particle physics, in which the W boson mass can be raised slightly relative to Standard Model predictions without affecting other current experiments.) The math required is still pre-university level, though complex numbers … Read more

Fourth Step in the Triplet Model is up.

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Advanced particle physics today: Today we move deeper into the reader-requested explanation of the “triplet model,”  (a classic and simple variation on the Standard Model of particle physics, in which the W boson mass can be raised slightly relative to Standard Model predictions without affecting other current experiments.) The math required is still pre-university level, though … Read more

So What Is It???

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So What Is It? That’s the question one hears in all the bars and on all the street corners and on every Twitter feed and in the whispering of the wind. Everybody wants to know. That bump seen on the ATLAS and CMS two-photon plots! What… IS… it…?

ATLAS_CMS_diphoton_2015
The two-photon results from ATLAS (top) and CMS (bottom) aligned, so that the 600, 700 and 800 GeV locations (blue vertical lines) line up almost perfectly. The peaks in the two data sets are in about the same location. ATLAS’s is larger and also wider. Click here for more commentary.

Well, to be honest, probably it’s just that: a bump on a plot. But just in case it’s not — just in case it really is the sign of a new particle in Large Hadron Collider [LHC] data — let me (start to) address the question.

First: what it isn’t. It can’t just be a second Higgs particle (a heavier version of the one found in 2012) that is just appended to the known particles, with no other particles added in.  

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Exciting Day Ahead at LHC

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At CERN, the laboratory that hosts the Large Hadron Collider [LHC]. Four years ago, almost to the day. Fabiola Gianotti, spokesperson for the ATLAS experiment, delivered the first talk in a presentation on 2011 LHC data. Speaking to the assembled scientists and dignitaries, she presented the message that energized the physics community: a little bump had shown up on a plot.

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