On local TV last night, I somehow got reporter Dave Malkoff to take a stab at explaining quantum field theory: the world is made of fields, but we only notice the ripples within them, which we see as particles. Something about Angelina Jolie in there at the end as well.
Higgs Ripples in the Koi Pond Read More »
Jorge Cham visits CERN, and comes back with tales of particles and mass.
PhD Comics Explains the Higgs Boson Read More »
A flowchart I put together for The Particle at the End of the Universe. Feel free to spread around, with appropriate attribution.
Sorry for the tiny writing, there are a lot of particles! Click to embiggen and get a legible version.
What Particle Are You? Read More »
Update: here’s the amazon page, where the book is ready for pre-order.
Speaking of writing popular books, I’m at it again. I’m currently hard at work writing The Particle At the End of the Universe, a popular-level book on the Large Hadron Collider and the search for the Higgs boson. If all goes well, it should appear in bookstores at the end of this year or beginning of next. (Ideally, it will go on sale the same day they announce the discovery of the Higgs. I’m trying to bribe the right people to make that happen.) The title is somewhat tentative, so it might change at some point.
This will be a somewhat different book than From Eternity to Here. While both are aimed at a general audience, FETH was a rather lengthy tome that made a careful argument in a hopefully novel way. Anyone could read it, but to get the most out of it you have to really sit and think about certain ideas. Particle, on the other hand, aims to be a fun and narratively gripping page-turner — a book that makes you eager to move quickly to the next chapter, rather than taking a few minutes to let the last one sink into your head. A bodice-ripper, if you will. It will be full of stories and fun anecdotes about the human beings who made the LHC happen and have devoted their lives to searching for the Higgs and particles beyond the Standard Model. A book you would be happy to give to your Grandmom in order to convey some of the excitement of modern physics. (Unless your Grandmom is a particle physicist, in which case she might think it’s at too low a level.)
At the same time, of course, I’m going to try to illuminate the central ideas of the Standard Model in as clear a fashion as I can manage. It won’t just be a list of particles; I’ll cover field theory, gauge bosons, and spontaneous symmetry breaking. All in fine bodice-ripping style. (Maybe get Fabio for the cover?)
If you are a particle physicist yourself, I’m happy to take input. This could take the form of a favorite analogy you like to use to explain some subtle concept, or some physics idea or piece of history you think really doesn’t get the attention it deserves in the popular media. Even better if you have some personal involvement in a fun story — you lost your virginity in the LHC tunnel, or you discovered asymptotic freedom but didn’t get around to publishing it. I’m talking to as many physicists as I can, but I can’t talk to everyone. I’m looking for tales that will make the human side of physics come alive.
Also happy to take input if you’re not a particle physicist! What are the concepts that we don’t do a good job explaining? What are the buzzwords you’ve heard about the don’t make sense? The questions you really want answered?
I sincerely believe the search for the Higgs and whatever might lie beyond is a Big Deal in the history of science, and I hope to convey some of the importance and excitement of this question to as large an audience as possible. I’ll be flitting around the country giving talks when the book comes out, so let me know if you have a big lecture hall full of eager minds that want to hear the latest dispatches from the particle trenches. Should be a fun ride.
The Particle At the End of the Universe Read More »
Can you think of any?
Here’s what I mean. When we set about justifying basic research in fundamental science, we tend to offer multiple rationales. One (the easy and most obviously legitimate one) is that we’re simply curious about how the world works, and discovery is its own reward. But often we trot out another one: the claim that applied research and real technological advances very often spring from basic research with no specific technological goal. Faraday wasn’t thinking of electronic gizmos when he helped pioneer modern electromagnetism, and the inventors of quantum mechanics weren’t thinking of semiconductors and lasers. They just wanted to figure out how nature works, and the applications came later.
So what about contemporary particle physics, and the Higgs boson in particular? We’re spending a lot of money to look for it, and I’m perfectly comfortable justifying that expense by the purely intellectual reward associated with understanding the missing piece of the Standard Model of particle physics. But inevitably we also mention that, even if we don’t know what it will be right now, it’s likely (or some go so far as to say “inevitable”) that someday we’ll invent some marvelous bit of technology that makes crucial use of what we learned from studying the Higgs.
So — anyone have any guesses as to what that might be? You are permitted to think broadly here. We’re obviously not expecting something within a few years after we find the little bugger. So imagine that we have discovered it, and if you like you can imagine we have the technology to create Higgses with a lot less overhead than a kilometers-across particle accelerator. We have a heavy and short-lived elementary particle that couples preferentially to other heavy particles, and represents ripples in the background field that breaks electroweak symmetry and therefore provides mass. What could we possibly do with it?
Specificity and plausibility will be rewarded. (Although there are no actual rewards offered.) So “cure cancer” gets low marks, while “improve the rate of this specific important chemical reaction” would be a lot better.
Let your science-fiction-trained imaginations rome, and chime in.
Technological Applications of the Higgs Boson Read More »
The news from Geneva this morning is in. Essentials: what we’re seeing is pretty consistent with the existence of a Higgs boson around 123-126 GeV. The data aren’t nearly conclusive enough to say that it’s definitely there. But the LHC is purring along, and a year from now we’ll know a lot more.
It’s like rushing to the tree on Christmas morning, ripping open a giant box, and finding a small note that says “Santa is on his way! Hang in there!” The LHC is real and Santa is not, but you know what I mean.
Here are the technical write-ups from ATLAS and CMS. For stories and some live-blogs, check out Philip Gibbs, Matt Strassler, Aidan Randle-Conde, Ken Bloom, or Jester. Or if you just want the bottom line sigmas, Jim Rohlf provides them. ATLAS gives 3.6 sigma local significance, 2.3 sigma global significance; CMS gives 2.6 sigma local significance, 1.9 sigma global significance (although CMS points to about 124 GeV, while ATLAS points to about 126, which might be important). The difference between “local” and “global” is that the first asks “if I were only looking at this one point in parameter space, how surprising would the result be?”, while the latter asks “what is the chance I would find this kind of deviation somewhere in parameter space?” Nominally the global significance is obviously more relevant, although one could argue that we have good reasons to expect that the Higgs is actually lurking right there, so the local significance isn’t completely cheating.
Let’s put it this way: if we were testing a theory that everyone thought was wrong, rather than one that everyone thinks is right, nobody would take these results as strong indications that the idea was correct. We have a strong theoretical bias that the Higgs exists and is somewhere close to this mass range, so it’s completely reasonable to think that we are seeing hints (tantalizing ones!) that it’s there, but wait-and-see is still the right attitude.
Here are the simplest plots I could find. First the full analysis from ATLAS (zoomed in on the interesting region), via Philip Gibbs’s blog.:
Then from CMS, via Ken Bloom:
These plots are complicated because they’re trying to tell you two things at once. The black curve is the data, the green/yellow bands are the expected ranges of the data at 1 sigma and 2 sigma. If all you want to do is ask whether we can exclude the Higgs in a certain range, just check whether the black band is below the value 1. But if you want to say you have evidence for the Higgs, you need the black line to wander above the yellow band (or higher, if you want more than 2 sigma [and you do]). So ATLAS sees something at 126 GeV, CMS is at least consistent with 123-124 GeV (although it doesn’t see much at 126).
As Sarah Kavassalis puts it, the real message today is that the LHC is working great. 2012 will bring another year of data, hopefully at even higher luminosity (so many more total events). The Higgs has been around for 13.7 billion years, it will still be there tomorrow.
Science! It Marches On Read More »
Tomorrow, Tuesday 13 December, there will be a couple of seminars at CERN presented by Fabiola Gianotti and Guido Tonelli, speaking respectively for the ATLAS and CMS collaborations at the LHC. They will be updating us on the current status of the search for the Higgs boson. The seminars will be webcast from CERN, and there should be a liveblog on Twitter that you can follow by searching for the #higgsliveblog hashtag (no Twitter account required). The seminars start at 14:00 Geneva time, so that’s 5:00 a.m. Pacific time if I do my calculations correctly. Of course there will be plenty of news coverage immediately thereafter, so don’t feel too bad if you sleep through it. Many places with LHC physicists (including Caltech) are also having their own local seminars. Should be exciting!
If you want to know why it’s exciting, after you’ve read John’s description of life in the trenches and Matt Strassler’s post about the multiple stages of hunting the Higgs and mine about why we need something like it, see even more recent posts by Matt, Jester, and Pauline Gagnon. Reader’s Digest version: not only are we being updated on the status of the search, there are believable rumors that the searches are actually seeing something — hints of a Higgs near 125 GeV, with better than 3-sigma significance from ATLAS and better than 2-sigma significance from CMS. But obviously rumors are no match for what actually happens.
All I’m here to tell you is: you should not expect to hear anyone announcing that we have discovered the Higgs boson. This will, at best, be a hint — “evidence for” something, not “discovery of” that thing. The collaborations realistically can’t claim to have actually discovered the Higgs, even if it’s there — they don’t have enough data. (CERN even issued a press release to drive home the point.) And in the real world, hints are sometimes misleading. That is: the experimenters will give us their absolute best judgment about what they are seeing, but at this stage of the game that judgment is necessarily extremely preliminary. If they say “we have 3.5-sigma evidence, which is quite suggestive,” do not think that they are just being coy and what they really mean is “oh, we know it’s there, we just have to follow the protocols.” The protocols are there for a reason! Mostly, that many 3-sigma findings eventually go away. This is one step on a journey, not the culmination of anything. (For Americans out there: it’s like a bill has been passed by the House, but not yet passed by the Senate, and certainly not signed by the President. Much can go wrong along the way.)
The journey of a thousand miles begins with a single step. It’s possible that tomorrow’s announcement means that we’re nearing the end of the journey, say at the mile-990 marker. But we can’t be sure, and there are no royal roads to particle physics. Patience! The excitement of not knowing for sure is what makes science one of the most compelling human stories.
Not Being Announced Tomorrow: Discovery of the Higgs Boson Read More »
Perhaps you’ve heard of the Higgs boson. Perhaps you’ve heard the phrase “desperately seeking” in this context. We need it, but so far we can’t find it. This all might change soon — there are seminars scheduled at CERN by both of the big LHC collaborations, to update us on their progress in looking for the Higgs, and there are rumors they might even bring us good news. You know what they say about rumors: sometimes they’re true, and sometimes they’re false.
So we’re very happy to welcome a guest post by Matt Strassler, who is an expert particle theorist, to help explain what’s at stake and where the search for the Higgs might lead. Matt has made numerous important contributions, from phenomenology to string theory, and has recently launched the website Of Particular Significance, aimed at making modern particle physics accessible to a wide audience. Go there for a treasure trove of explanatory articles, growing at an impressive pace.
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After this year’s very successful run of the Large Hadron Collider (LHC), the world’s most powerful particle accelerator, a sense of great excitement is beginning to pervade the high-energy particle physics community. The search for the Higgs particle… or particles… or whatever appears in its place… has entered a crucial stage.
We’re now deep into Phase 1 of this search, in which the LHC experiments ATLAS and CMS are looking for the simplest possible Higgs particle. This unadorned version of the Higgs particle is usually called the Standard Model Higgs, or “SM Higgs” for short. The end of Phase 1 looks to be at most a year away, and possibly much sooner. Within that time, either the SM Higgs will show up, or it will be ruled out once and for all, forcing an experimental search for more exotic types of Higgs particles. Either way, it’s a turning point in the history of our efforts to understand nature’s elementary laws.
This moment has been a long time coming. I’ve been working as a scientist for over twenty years, and for a third decade before that I was reading layperson’s articles about particle physics, and attending public lectures by my predecessors. Even then, the Higgs particle was a profound mystery. Within the Standard Model (the equations that used at the LHC to describe all the particles and forces of nature we know about so far, along with the SM Higgs field and particle) it stood out as a bit different, a bit ad hoc, something not quite like the others. It has always been widely suspected that the full story might be more complicated. Already in the 1970s and 1980s there were speculative variants of the Standard Model’s equations containing several types of Higgs particles, and other versions with a more complicated Higgs field and no Higgs particle — with a key role of the Higgs particle being played by other new particles and forces.
But everyone also knew this: you could not simply take the equations of the Standard Model, strip the Higgs particle out, and put nothing back in its place. The resulting equations would not form a complete theory; they would be self-inconsistent. …
Guest Post: Matt Strassler on Hunting for the HiggsRead More »
Guest Post: Matt Strassler on Hunting for the Higgs Read More »
In the comments to the previous post, Monty asks a perfectly good question, which can be shortened to: “Is the Higgs boson really necessary?” The answer is a qualified “yes” — we need the Higgs boson, or something like it. That is, we can’t simply take the Standard Model as we know it and extend it to arbitrarily high energies without new physics kicking in.
The role of the Higgs field is to break the symmetry of the electroweak interactions, as discussed here. We think that there is a lot of symmetry underlying particle interactions, but that much of it is hidden from our low-energy view. In technical terms, the electroweak theory of Glashow, Weinberg and Salam posits an “SU(2)xU(1)” symmetry, that somehow gets broken down to “U(1).” That unbroken symmetry gives us electromagnetism, a force carried by a massless particle, the photon. The broken symmetries are still there, but their force-carrying particles become massive when the symmetry breaks — those are the W+, W–, and Z0 bosons.
There’s no question that something breaks the symmetry. The question that is worth asking is: “Can we imagine breaking the symmetry without introducing any new particles?”
…
Why We Need the Higgs, or Something Like It Read More »
Winner of the coveted “Best Paper Title Among Today’s arXiv Postings.”
Higgs in Space!
C.B. Jackson, Geraldine Servant, Gabe Shaughnessy, Tim M.P. Tait, Marco TaosoAbstract: We consider the possibility that the Higgs can be produced in dark matter annihilations, appearing as a line in the spectrum of gamma rays at an energy determined by the masses of the WIMP and the Higgs itself. We argue that this phenomenon occurs generally in models in which the the dark sector has large couplings to the most massive states of the SM and provide a simple example inspired by the Randall-Sundrum vision of dark matter, whose 4d dual corresponds to electroweak symmetry-breaking by strong dynamics which respect global symmetries that guarantee a stable WIMP. The dark matter is a Dirac fermion that couples to a Z’ acting as a portal to the Standard Model through its strong coupling to top quarks. Annihilation into light standard model degrees of freedom is suppressed and generates a feeble continuum spectrum of gamma rays. Loops of top quarks mediate annihilation into gamma Z, gamma h, and gamma Z’, providing a forest of lines in the spectrum. Such models can be probed by the Fermi/GLAST satellite and ground-based Air Cherenkov telescopes.
And for those who don’t immediately get the joke, we dip once more into the limitless supply of Muppets videos on YouTube.