Over on the Google+, I linked to an informal essay by John Norton, in which he recounts the activities of a workshop on QFT at the Center for the Philosophy of Science at the University of Pittsburgh last October. In Norton’s telling, the important conceptual divide was between those who want to study “axiomatic” QFT on the one hand, and those who want to study “heuristic” QFT on the other. Axiomatic QFT is an attempt to make everything absolutely perfectly mathematically rigorous. It is severely handicapped by the fact that it is nearly impossible to get results in QFT that are both interesting and rigorous. Heuristic QFT, on the other hand, is what the vast majority of working field theorists actually do — putting aside delicate questions of whether series converge and integrals are well defined, and instead leaping forward and attempting to match predictions to the data. Philosophers like things to be well-defined, so it’s not surprising that many of them are sympathetic to the axiomatic QFT program, tangible results be damned.

The question of whether or not the interesting parts of QFT can be made rigorous is a good one, but not one that keeps many physicists awake at night. All of the difficulty in making QFT rigorous can be traced to what happens at very short distances and very high energies. And that’s certainly important to understand. But the great insight of Ken Wilson and the effective field theory approach is that, as far as particle physics is concerned, it just doesn’t matter. Many different things can happen at high energies, and we can still get the same low-energy physics at the end of the day. So putting great intellectual effort into “doing things right” at high energies might be misplaced, at least until we actually have some data about what is going on there.

Something like that attitude is defended here by our former guest blogger David Wallace. (Hat tip to Cliff Harvey on G+.) Not the best video quality, but here is David trying to convince his philosophy colleagues to concentrate on “Lagrangian QFT,” which is essentially what Norton called “heuristic QFT,” rather than axiomatic QFT. His reasoning very much follows the Wilsonian effective field theory approach.

The concluding quote says it all:

LQFT is the most successful, precise scientific theory in human history. Insofar as philosophy of physics is about drawing conclusions about the world from our best physical theories, LQFT is the place to look.

Working out the numbers, the chances of 14 coin flips in a row being equal is 1 in 8,192. (The linked article says 1 in 16,000, which comes from 2^14; but that first coin flip has to be something, so the chances of 14 in a row are really 1 in 2^13. The anomaly would be just as strange if the AFC had won every time.) That’s a better than 3.8-sigma effect! Enough to call a press conference, if this were particle physics.

The question is … is this really a signal, or did we just get lucky? Is it a fair coin and the NFC has just been the happy recipient of a statistical fluctuation, or is there something fishy about the coin? Remember Barry Greenstein’s parable about how different people compute probabilities.

And let it be a lesson the next time you’re excited about 3-sigma anomalies.

So now an official boycott has been organized, and is gaining steam — if you’re a working scientist, feel free to add your signature. Many bloggers have chimed in, e.g. Cosma Shalizi and Scott Aaronson. Almost all scientists want their papers to be widely accessible — given all the readily available alternatives to Elsevier (including the new Physical Review X), all we need to do is self-organize a bit and we can make it happen.

Thing the first is that Morgan Freeman, many years before he went through the wormhole, was a regular on The Electric Company, along with performers like Rita Moreno and Bill Cosby. (Via Quantum Diaries, of all places.) This was public television’s show from the 70′s that was meant for kids who had moved on from Sesame Street — I was more of a Zoom kid myself, but I must have seen Electric Company episodes with Freeman playing hip dude Easy Reader.

Thing the second is that Easy Reader’s theme song, sung in the clip above, is a dead ringer for Amy Winehouse’s “Rehab.” Flip back and forth between playing them if you don’t believe me. So much so, I am told, that DJ’s in clubs will sometimes mix the two tunes together. Not at the clubs I go to, I guess.

Given the inspiration of the looming Hubble Space Telescope deadline, I thought I would share some of my “big picture” views on crafting successful proposals, expanding significantly on the more succinct advice given in an earlier post. While I’ve developed these opinions based on my experience in astronomy, I suspect they’d apply to many other fields, both within and beyond science. So here goes…

A Proposal is a Highly Structured Rigorous Argument

In its most abstract form, a proposal is a piece of persuasive writing that lays out a convincing case that the proposed research is:

1. important
2. feasible
3. efficient

By “important”, I mean that the project must rise above the level of “good to do”, and instead be seen as “must be done”, even by people who don’t work in the field. By “feasible”, I mean that there must be a clear path to a definitive scientific result. By “efficient”, I mean that the particular approach you’ve taken is the optimal one for reaching the important goals you’re targeting (i.e. aim for “Studying X provides the cleanest test of Important Science Y” and avoid building a proposal to study X when studying Z is clearly a more direct approach to Important Science Y — even if you worked on X for your thesis.)

You should lay out your arguments for Every. Single. One. of these cases before you write a single word of latex. Why? Because proposals live or die not on the beauty of your prose, but on the structure of your argument. If the reviewer does not believe that you’ve made the case for importance, feasibility, and efficiency, you’re done.

Here’s how I do this. Although I’m sure it will seem remedial to many of you, and reveal me as the anal geek that I am, I start a stupid ASCII file with two sections:

1. Selling Points
2. Potential Weaknesses to Shore Up

I then start filling out each with short bullet points listing every possible argument for or against what I’m proposing.

The selling points should be fairly easy, since you’re likely to write proposals for things you are inclined to think are awesome. Do, however, avoid the pitfall of conflating “important to me” with “important to Science”. Just because you would really like to know more about some property of something you’re interested in, doesn’t mean that other people will naturally share your enthusiasm. Keep your eye on the big picture.

The “Potential Weaknesses” section can be a bit trickier, since you need to channel your inner crabby reviewer. Think of every nit-picky, outside the box criticism one could throw at your idea, and every area where a reviewer could get confused. (As an example, here’s a list of some of the self-criticisms I came up with for an HST proposal for NIR observations of nearby galaxies a few years back: “What about AO from the ground?” “Why this many targets — how many do you actually need?” “What about dust (i.e. is 1 NIR filter OK)?” “Are the models really in need of improvement?” “How can we claim to do galaxy science while simultaneously arguing that the models aren’t yet up to it?” “Are the results confused depending on fraction of O-rich vs C-rich AGB?” etc).

In short, the “Selling Points” section is about demonstrating “importance”, and the “Potential Weaknesses” section is about assessing “feasibility” and “efficiency”.

After you’ve got an initial list, you have to step back, evaluate, and edit.

• Go through the selling points and prioritize. Decide what the “main message” of your proposal is, based on which bullet points speak most effectively to the larger importance of what you’re proposing. If your ideas are strong, you’ll usually find that several of the most compelling bullet points will group together and can be ordered to tell a single story. You’ll also find that some of the bullet points will not naturally fit within that narrative. Identify this subset of arguments that are “nice, but not compelling”. You’ll want to be sure to minimize these in the proposal, to avoid their distracting from a more central idea. I speak from experience when I say that you really do not want to confuse the reviewers about what your proposal is about (i.e. It’s better to have something like “Dark Matter! Dark Matter! Dark Matter! and by the way it also tells you something about planets, frogs, and quark stars” rather than “Dark Matter! Planets! Frogs! Quark Stars!”, since the latter leads to complaints from the reviewers that while they believed your dark matter ideas, you had not fully fleshed out a compelling case for the frog science.)
• For each entry in the “Potential Weakness” section, write down any brief ideas about addressing those concerns (something like “Make figure showing evolution of models with time” “Check number of stars expected and compare to sizes of Galactic samples”, etc). You don’t have to come up with definitive answers, but you should lay out a road map for what you need to do to make your experiment look feasible and efficient.

At this point, I sometimes make a third section and list a few figures that seem like they support the key scientific ideas, or that shore up some of the obvious weaknesses.

Now that you have this silly little ASCII file (which you shouldn’t spend more than a day on, if that), send it to your collaborators. Get their feedback about what they think the strongest selling points are, what their additional concerns are, and what arguments they would use to shore up weaknesses. Expand the file accordingly, so you have a record of everything that you think needs to go into the proposal. You’ll probably find that it’s a huge time savings to get this to your collaborators in this form, before you have a 10 page latex file with embedded figures. If you do the latter, your collaborator will likely come back and say “You know, I think the reviewers are going to be way more interested in frogs”, at which point you have to chuck out weeks of work. With this method, you get feedback quickly (since they have to skim a very short list of bullet points), and you don’t have a lot of sunk costs if you decide to overhaul the arguement.

At this point you’ll have a document that summarizes your rhetorical argument. Your case will be laid out so that you can easily evaluate it on its scientific merits. So, before you dive into writing, you need to step back and decide if you’ve actually constructed a strong case. Sometimes, it will become obvious that there are too many weaknesses to address, and that it’s going to be an uphill battle to convince anyone that this needs to be done. If that’s the case DON’T WRITE THE PROPOSAL! I have probably a half dozen of these ASCII files where I spent half a day deciding that I didn’t, in fact, have a compelling project, and I’d be better off investing my time elsewhere. That’s OK! The exercise of structuring your argument first is designed to be fast, so you don’t sink much time in before you decide whether to continue or not.

Once you (and your collaborators) are convinced that you do in fact have a strong case, you need to start building the actual text. I frequently will estimate the number of paragraphs I expect to have for my scientific justification (usually 2.5-3 per page), and then make an enumerated list showing how the argument will flow through the paragraphs. This exercise helps to keep the text following the structure of the argument, so that it builds to make the main points. It also helps me to figure out when I’m trying to cram too much information in.

If you’ve gone through all of the above, you’ll find that the proposal will almost write itself. You will have cleanly separated “generating text” from “generating a compelling project”, such that you know exactly what you want to convey, and what the text needs to accomplish. Generating lovely English sentences at this point is much easier.

I was invited to contribute, but wasn’t feeling very imaginative, so I moved quickly and picked one of the most obvious elegant explanations of all time: Einstein’s explanation for the universality of gravitation in terms of the curvature of spacetime. Steve Giddings and Roger Highfield had the same idea, although Steve rightly points out that Einstein won’t really end up having the final word on spacetime. Lenny Susskind picks Boltzmann’s explanation of why entropy increases as his favorite explanation, and mentions the puzzle of why entropy was lower in the past as his favorite unsolved problem — couldn’t have said it better myself. For those of you how prefer a little provocation, Martin Rees picks the anthropic principle.

But as usual, the most interesting responses to me are those from far outside physics. What’s your favorite?

Full text of my entry below the fold.

Einstein Explains Why Gravity Is Universal

The ancient Greeks believed that heavier objects fall faster than lighter ones. They had good reason to do so; a heavy stone falls quickly, while a light piece of paper flutters gently to the ground. But a thought experiment by Galileo pointed out a flaw. Imagine taking the piece of paper and tying it to the stone. Together, the new system is heavier than either of its components, and should fall faster. But in reality, the piece of paper slows down the descent of the stone.

Galileo argued that the rate at which objects fall would actually be a universal quantity, independent of their mass or their composition, if it weren’t for the interference of air resistance. Apollo 15 astronaut Dave Scott once illustrated this point by dropping a feather and a hammer while standing in vacuum on the surface of the Moon; as Galileo predicted, they fell at the same rate.

Subsequently, many scientists wondered why this should be the case. In contrast to gravity, particles in an electric field can respond very differently; positive charges are pushed one way, negative charges the other, and neutral particles not at all. But gravity is universal; everything responds to it in the same way.

Thinking about this problem led Albert Einstein to what he called “the happiest thought of my life.” Imagine an astronaut in a spaceship with no windows, and no other way to peer at the outside world. If the ship were far away from any stars or planets, everything inside would be in free fall, there would be no gravitational field to push them around. But put the ship in orbit around a massive object, where gravity is considerable. Everything inside will still be in free fall: because all objects are affected by gravity in the same way, no one object is pushed toward or away from any other one. Sticking just to what is observed inside the spaceship, there’s no way we could detect the existence of gravity.

Einstein, in his genius, realized the profound implication of this situation: if gravity affects everything equally, it’s not right to think of gravity as a “force” at all. Rather, gravity is a feature of spacetime itself, through which all objects move. In particular, gravity is the curvature of spacetime. The space and time through which we move are not fixed and absolute, as Newton would have had it; they bend and stretch due to the influence of matter and energy. In response, objects are pushed in different directions by spacetime’s curvature, a phenomenon we call “gravity.” Using a combination of intimidating mathematics and unparalleled physical intuition, Einstein was able to explain a puzzle that had been unsolved since Galileo’s time.

The bad news: Sheldon Cooper makes fun of you on national TV.

Of course you don’t need to watch the ceremonies to learn what all the scientists are wearing this year. I am reliably informed that a regular tuxedo is not good enough; you need to go full white tie and tails. (Interestingly, the Peace Prize is more casual; black tie or “national costume” is perfectly acceptable.)

We’ve discussed this question before, and the idea of reproduction looms large in many people’s definitions of life. But I don’t think it really belongs. If you built an organism from scratch, that was as complicated and organic and lifelike as any living thing currently walking this Earth, except that it had no reproductive capacity, it would be silly to exclude it from “life” just because it was non-reproducing. Even worse, I realized that I myself wouldn’t even qualify as alive under Trifonov’s definition, since I don’t have kids and don’t plan on having any. (And no, those lawsuits were frivolous and the court records were sealed.)

It’s the yellow-taxi problem: in a city where all cars are blue except for taxis, which are yellow, it’s tempting to define “taxi” as “a yellow car.” But that doesn’t get anywhere near the essence of taxi-ness. Likewise, living species generally reproduce themselves; but that’s not really what makes them alive. Not that I have the one true definition (and maybe there shouldn’t be one). But any such definition better capture the idea of an ongoing complex material process far from equilibrium, or it’s barking up the wrong Tree.

Show this to your local climate denialist when they get confused about the distinction between “climate” and “weather.” Not that it will change their minds, but the dog is cute.

Stephen Hawking is celebrating his 70th birthday today. That in itself is an amazing fact, just as it was amazing when he celebrated his 40th, and 50th, and 60th birthdays, as well as every other day he’s lived and thrived with a debilitating neuron disease. The extra fact that he continues to make contributions to science pushes beyond amazing to practically unbelievable.

Everyone likes to tell Hawking stories, and this blog is no exception. So here is mine, meagre as it is. I’ve gotten more than enough mileage out of this one in person, I might as well put it on the blog so I won’t be tempted to tell it any more.

At the end of 1992 I was a finishing grad student, applying for postdocs. One of the places I applied was Cambridge, to Hawking’s group at DAMTP. There is a slight potential barrier for American students to travel to the UK for postdocs, so they like to get out ahead of things and offer jobs early. Unfortunately I was out of my office the day Hawking called to offer me a position. Fortunately, my future-Nobel-Laureate officemate was there, and he took the call. He explained that Stephen Hawking had called to offer me a job — I was thrilled about the offer, but understood “Hawking called” as metaphorical. But no, Brian later convinced me that it actually was Hawking on the other end of the line, which he described as a somewhat surreal experience. Of course after the initial introduction the phone gets handed over to someone else, but still.

Cambridge is one of the world’s best places to do theoretical physics, and I was sorely tempted, but I ended up going to MIT instead. Three years later, I went through the process again, as postdocs typically do. And again Cambridge offered me the job — and again, after a very tough decision, I said no, heading of the the ITP in Santa Barbara instead.

Up to this point I had never actually met Hawking in person, although I had been in the audience for one of his lectures. But every year he visits Caltech and Santa Barbara, so I finally got to be with him in the same place. The first time he visited he brought along a young grad student named Raphael Bousso, who has gone on to do quite well for himself in his own right. As a group of us went to lunch, I mentioned to Raphael that I had never said hi to Stephen in person, so I’d appreciate it if he would introduce us. But, I cautioned, I hope he wasn’t upset with me, because he had offered me a postdoc and I turned it down.

Raphael just laughed and said, “Don’t worry, there’s this one guy who he offered a postdoc to twice, and he turned it down both times!” So I had to explain that this guy was actually me. At which point Raphael ran up to Hawking, exclaiming “Stephen! Stephen, this is the guy — the one who turned down DAMTP for postdocs twice in a row!”

That was my personal introduction to Stephen. He just smiled, no big deal — life goes on for him whether or not some callow American student wants to fly across the puddle to work as a postdoc.

Since then I’ve had the privilege of interacting with Hawking more substantively a few times. Once a long conversation just after the discovery of the acceleration of the universe, when he was interested in hearing more about the supernova observations. And once at a whisky tasting organized at an international cosmology conference. Handicaps notwithstanding, Hawking never misses a chance to experience life to its fullest. Another time when I picked up him and his retinue at the airport — which gave me a tiny glimpse of the massive logistical operation it is to move Hawking from place to place. The simplest things that we take for granted are for him an elaborate production.

Happy birthday, Stephen. I know I won’t make the contributions you have to science, but I hope I can live as long, and approach life with your gusto and good humor.

1. Freely-falling objects will accelerate toward the ground at an approximately constant rate, up to corrections due to air resistance.

2. Of all the Radium-226 nuclei on the Earth today, 0.04% will decay by the end of the year.

3. A line drawn between any planet (or even dwarf planet) and the Sun will sweep out equal areas in equal times.

4. Hurricanes in the Northern hemisphere will rotate counterclockwise as seen from above.

5. The pressure of a gas squeezed in a piston will rise inversely with the change in volume.

6. Electric charges in motion will give rise to magnetic fields.

7. The energy of an object at rest whose mass decreases will also decrease, by the change in mass times the speed of light squared.

8. The content of the world’s genomes will gradually evolve in ways determined by fitness in a given environment, sexual selection, and random chance.

9. The entropy of closed systems will increase.

10. People will do many stupid things, and some surprisingly smart ones.

Happy New Year, everyone.

This year I’ve decided to confront the problem pluralistically. Thus: here we have five different Top Five lists, chosen according to completely different criteria. Let us know if your favorite Cosmic Variance post of the year somehow managed to not be on any of the lists.

First, the most crude and common measure, the posts with the most page views this year.

• Ten Things Everyone Should Know About Time
• I’m Too Smart to Understand Human Beings
• Faster-Than-Light Neutrinos
• Dark Energy FAQ
• Physics and the Immortality of the Soul

Next up, an equally quantitative and misleading measure of popularity: the top five posts by number of comments.

• Live-Blogging Curiosity, Hawking, and God
• Ten Things Everyone Should Know About Time
• Physics and the Immortality of the Soul
• Do You Think Inflation Probably Happened?
• Hell

Since I know they won’t do it themselves, here are my five favorite posts by the CV co-bloggers:

• Unsolicited Advice XI: How to Write a 5 Minute Talk, by Julianne
• The Scientific Method is Alive and Well, by Daniel
• The Aftermath of the Clown Murders, by Julianne
• James Webb Space Telescope, by Risa
• Making the (Higgs) Sausage, by John

And here are my top five favorite guest posts, in a very strong year:

• The Era of Dark Matter Direct Detection, by Neal Weiner
• The Quantum Mechanics of Source Code, by Jim Kakalios
• Contra Eternal Inflation, by Tom Banks
• Hunting for the Higgs, by Matt Strassler
• First Glimpse of the Higgs Boson, by Jack Gunion

Finally, here are my top five favorite posts by me, excluding the ones that made the first two lists. Be thankful I was able to restrain myself to only choosing five.

• Scientists Aren’t Always Complete Idiots
• Dark Matter: Just Fine, Thanks
• Are Many-Worlds and the Multiverse the Same Idea?
• Free Will is as Real as Baseball
• What Can We Know About the World Without Looking at It?

A successful year overall — I think Sept/Oct/Nov of 2011 were our highest-traffic months of all time. Here’s to seeing you all in 2012!

Here’s a legitimately touching Xmas song, Tim Minchin’s White Wine in the Sun (indirectly via Balloon Juice). As an Australian, he has a warmer image of the season than we Northerners. This isn’t the one that got censored from British TV, which is more amusing than heartwarming, but also worth a listen.

That popularity really bugs some people. Sales figures notwithstanding, Larsson’s books fall pretty dramatically short on several conventional metrics of literary quality, such as “elegance of writing” and “plausibility of plot.” Early in the first novel, before we really know what’s going on or have been properly introduced to most of the characters, we are treated to a scene that consists of one character telling another about a long series of complicated and shady European business deals, complete with obscure acronyms and names that will never be mentioned again. This keeps up for what seems like pages. And it’s just a hint of the various stylistic crimes Larsson will gleefully commit throughout the series. He loves piling on meaningless details, especially about what his characters are eating and the clothes they are wearing. The prose is clunky and often wearying. The series effectively evokes the brooding coldness of Scandinavian winters, but that’s not always a good thing.

And yet — the books are impossible to put down, as approximately 9 million readers will testify. (I haven’t seen the American movie, although I did see the Swedish one, which wasn’t anywhere near as gripping as the original novel.) So we have a fairly common occurrence in publishing: books that are fantastically popular, but nevertheless are not very “good” by many agreed-upon criteria. In very different ways, think of Dan Brown, JK Rowling, or Stephenie Meyer.

Faced with such a puzzling phenomenon, one can go two ways. One is to go all-out curmudgeon: take Michael Newman’s review of The Girl Who Kicked the Hornet’s Nest (many spoilers). It’s not so much a review as an extended whine of incomprehension: How can something so terrible be so beloved by so many people?

The other way, much more interesting, is to actually try to answer that question, rather than just repeat it in an increasingly petulant tone. What is it about these books that makes them so irresistible? In our electronically-focused age, when some good old-fashioned printed books reach dizzying heights of popularity, perhaps the thing to do isn’t to complain that they don’t fit into our pre-existing criteria, but to figure out what they are actually doing right. I personally loved Larsson’s books, and am quite fond of the Harry Potter series, but I would ask the same question about The Da Vinci Code or the Twilight books (the first of which I thought was terrible, and the second of which I was never tempted to pick up). It’s a commonplace to bemoan what a “bad writer” Dan Brown is, but that can’t really be true. People read the books with enjoyment and keep coming back for more; he must be doing something right. Not everything, of course — I doubt that it’s necessary to distort history and science so dramatically just to write a compelling thriller. (A special case would be something like Ayn Rand, whose writing is uniformly off-putting; people keep coming back for the politics, not for the prose.)

In the case of Stieg Larsson, Laura Miller gets it right in her own review of Hornet’s Nest. Say what you will about lumbering prose and distracting minutiae; Larsson has created unforgettable characters and put them in compelling situations. This isn’t a cheap skill that anyone can just pull off, or we’d all be living high off our royalty checks. (Or our heirs would be fighting over them.) When books work for people, it makes more sense to appreciate the craftsmanship than to complain that they don’t fit our criteria. I still don’t know how Dan Brown makes people want to compulsively turn the pages, but it’s no mean trick. More power to him.

The machinery can’t force Prof Haggard to do anything really complicated – “You can’t make me sign my name,” he says, almost ruefully – but at one point, Christina is able to waggle his index finger slightly, like a schoolmaster. It’s very fine control, a part of the brain specifically in command of a part of the body. “There’s quite a detailed map of the brain’s wiring to the body that you can build,” he tells me.

We sometimes say “the Large Hadron Collider is the most complex machine ever built,” but I’m not sure how it would directly compare to a human being. All part of the great bootstrap up to greater complexity, which will continue for a while until it all inevitably deteriorates into empty space.

Tuesday December 13 has been a very exciting day for particle physics. The ATLAS and CMS experiments at the Large Hadron Collider (LHC) announced today that they are both seeing hints of a Higgs boson with properties that are close to those expected for the Standard Model (SM) Higgs boson as originally proposed by Peter Higgs and others. While the “significance” of the signals has not yet reached “discovery level” (5 sigma in technical language) the two experiments both see signals that exceed 2 sigma so that there is less than a 5% chance that they are simply statistical fluctuations. Most persuasively, the signals in the channels with excellent mass determination (the photon-photon final decay state and the 4-lepton final state) are all consistent with a a Higgs boson mass of around 125 GeV IN BOTH EXPERIMENTS. This coincidence in mass between two totally independent experiments (as well as independent final states) is persuasive evidence that the photon-photon and 4-lepton excesses seen near 125 GeV are not mere statistical fluctuations.

Observation of the Higgs with approximately the SM-like rate suggests that to first approximation the Higgs is being produced as expected in the SM and that it also decays as predicted in the SM. Many theorists, including myself, have suggested that a Higgs might be produced as in the SM but might have extra decays that would have decreased the photon-photon and 4-lepton decay frequencies to an unobservable level, making the Higgs boson much harder to detect at the LHC. The level of the observed excesses argues against such extra decays being very important. The photon-photon and 4-lepton detection modes were originally proposed and shown to be viable for a SM-like Higgs boson by myself and collaborators (in particular, Gordy Kane and Jose Wudka) way back in 1986-1987. It has taken a long time (25 years) for the technology and funding to reach the point where these detection modes could be examined. I often joked that I was personally responsible for forcing each of the LHC collaborations to spend the 30 million dollars or so needed to build a photon detector with the energy resolution required. Fortunately, it seems that the money was well-spent and the ATLAS and CMS detectors both found ways to build the needed detectors, a real triumph of international collaboration and technical expertise. Also key is the very successful operation of the LHC that has produced the enormously large number of collision events needed to dig out the Higgs signal from uninteresting ‘background’ events. Until this summer produced the first very weak signs of the Higgs, I was beginning to wonder if the Higgs would be discovered during my lifetime. Fortunately, simplicity (i.e. a very conventional SM-like Higgs boson) seems to have prevailed and ended my wait.

Going forward, by the end of 2012 the levels of these excesses should reach the 5 sigma “discovery” level if the SM-like Higgs really does have the mass and decays indicated by current results. Further, we will begin to have some moderately precise (20%-30% or so?) measurements of the individual decay modes of the Higgs boson that might indicate just how precisely SM-like it is. Many theories beyond the Standard Model predict the possibility of deviations from the predictions of the purely SM Higgs boson. As data accumulate, looking for such deviations will be a major focus. Current data (weakly) hint at the possibility that the Higgs production rate might turn out to be modestly larger than predicted if the Higgs is that of the Standard Model and has mass of 125 GeV — the best-fit ATLAS cross section is about 1.5 times as large as the SM prediction, whereas the best-fit CMS cross section is very close to the SM prediction. Time (i.e. more accumulated data) will tell.

Of course, the current run of the LHC will be halted at the end of 2012, followed by a lengthy shut down for upgrades to the accelerator and to the detectors. After this upgrade, the LHC will operate at a much higher energy (14 TeV) compared to the current energy of 7 TeV, and, if all goes according to plan, have a much higher collision rate. At this point, precision studies of the Higgs boson will certainly be possible. If deviations are observed, then we will strongly suspect that the SM is incomplete. Even before that time, we are hoping that by the end of 2012 we will have seen new types of particles that do not fit into the Standard Model. This, for example, is predicted if the universe is supersymmetric. Supersymmetric models tend to predict a light Higgs boson that is fairly, but not completely, SM-like with mass in the range 110 GeV to 140 GeV and so are very consistent with what is being observed. If some supersymmetric particles (so called sparticles) are observed then their masses and properties constrain the Higgs mass in a given model and consistency of the entire theory can be nicely tested. Hopefully, some version of physics beyond the Standard Model will be directly observed at the LHC, in which case there will be at least a decade of exciting observations and analyses to determine the precise beyond-the-Standard-Model theory.

Still, the pure Standard Model with no new physics cannot be totally discarded. Although this would not allow a so-called “natural” explanation of the Z boson and Higgs boson masses, the pure SM is still internally consistent even at energies close to the Planck scale for a Higgs mass greater than or equal to about 125-130 GeV. In other words, the observed Higgs mass is on a borderline. Above 125-130 GeV, new physics below the Planck mass scale is not required for internal consistency of the SM. But, had the Higgs boson mass been significantly below this (the precise border being somewhat uncertain theoretically), the SM would necessarily break down at some energy scale below the Planck scale and at this lower energy scale new physics would have to enter. In short, a SM-like Higgs boson with mass near 125 GeV is maximally interesting from many theoretical perspectives.

In any case, theorists and experimentalists are all very relieved that the LHC appears to be observing a Higgs boson thereby ensuring an extremely interesting program of physics at the LHC for decades to come. Further, such a light SM-like Higgs boson provides strong motivation for a linear electron-positron collider of low center-of-mass energy. Studies suggest that only such a collider can easily measure the properties of such a light Higgs boson at the few percent level, although the LHC might not do that much worse depending upon future improvements and upgrades.

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.

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.

But, following on Matt Strassler’s excellent post about the physics, I thought it might be interesting to tell you what it’s been like this past year getting to this stage in this search. As you probably know, each of the two big experiments has over 3000 physicists participating, from all over the world. Many, but by no means the majority, are resident at CERN; most are at their home institutions in Europe, North America, and Asia and elsewhere.

The main thing that allows us to collaborate on a global scale like this is video conferencing. We used a system called EVO, developed at Caltech, which allows us to schedule meetings and connect to them from a laptop or desktop computer, or even dial in by phone. Sometimes it’s clear that people are connected by phone from the oddest places: once I heard the clear sounds of someone participating in the meeting from a train ride in Italy, oftentimes you hear people speak while they are driving the (hopefully with a hands-free device), and often one hears the sounds of children in the background (including my own). The issue is that meetings can be at any time of day for different people in different continents. Fortunately the experiments have gravitated toward having meetings in the late afternoon, Europe time, which makes it early morning for people like me in California.

A good thing about our videoconferencing system is that you actually have a choice whether or not to transmit or receive the video part of the meeting, which tends to be less useful than looking at material under discussion, which is usually in the form of PowerPoint slides. That makes it even easier to participate early in the morning! No one has to see you in your pajamas, and they probably don’t want to. I did it this morning, in fact, at 6 am.

So what are all these meetings? In CMS, our whole system of producing physics results has a sort of pyramidal structure. Each experiment has a number of physics analysis groups which meet a weekly or biweekly, typically, and have two “conveners” who set the agenda and run the meetings. These convener positions are typically held by senior people in the collaboration such as professors or senior lab scientists, for two years at a stretch, one convener changing out each year. They report to an overall physics coordinator and his or her deputies. Within the physics analysis groups are subgroups devoted to sets of analyses which share common themes, common tools, or similar approaches. Each of these subgroups in turn is led by a pair of conveners who establish the ongoing analyses and guide them to eventual approval within physics analysis group.

We have what I think is a pretty impressive internal website devoted to tracking the progress of each physics analysis. From a single website you can drill down into a particular physics group find the analysis you want get links to all the documentation, and follow what’s happening. In parallel, there is a web system for recording the material presented at every meeting.

The goal of every analysis is to be approved by its physics group, so it can be shown in public at conferences and seminars. This requires having complete documentation including internal notes with full details of the analysis, and a “public analysis summary” which is available to the public, and which often serves as the basis for a peer–reviewed paper which soon follows.

Every analysis is assigned an analysis review committee of three to five people with experience in the topic, who act as a sort of hit squad, keeping the analyzers on their toes with questions and comments at every stage of the analysis, both on the actual analysis details and on the documentation. After all, if we are not our own worst critics, someone else will gladly fill the role!

The process from initially recording data from proton–proton collisions to ultimate physics results can take months. By now the basic algorithms which are run on every collision in order to reconstruct what happened are well-established. But during the year the running conditions of the accelerator changed with ever–increasing rates of proton–proton collisions happening. In every 25 nanosecond “bunch crossing”, by the end of running this year we were recording an average of up to 10 proton–proton collisions. Typically only one of these is of interest and the rest are “minimum bias” events in which the protons strike glancing blows. Nevertheless, these additional interactions caused us a lot of trouble this year because they result in additional energy recorded by the detectors, additional charged tracks, and skew various quantities which we are trying to measure in each collision. This was one of the major challenges of 2011.

In parallel with processing the data that we record, we run full simulations of well–known standard model collision processes which represent our background when we are doing searches for new particles. There is a big organizational challenge in doing these simulations, which run on a worldwide grid of computers devoted to CMS data analysis. We make use of the Open Science Grid for this in the US, the EuroGrid in Europe, and other clusters scattered all around the world, comprising tens of thousands of computing nodes.

The basic idea of any new particle search is simple: you make a selection which retains as many collision events potentially coming from the new particle, while retaining as few background events as possible. Then you predict the number of background events from well-known processes, and see if any excess remains. Almost all analyses these days use the distribution of some final quantity (such as the estimated mass of the new particle) to look for these excesses. At this point one can then use statistical techniques to estimate the largest contribution that could be possible given the observed spectrum, or if there is an access, calculate the probability that the background alone could give rise to such an excess. This is how we quote the statistical significance of the results.

The details, though, boggle the mind. The graphic here shows the complexity of the statistical procedure for correctly keeping track of all the little correlations that can occur among and between the search channels. (This graphic is courtesy Kyle Cranmer of NYU, one of the main Higgs combiners in the ATLAS experiment.)

A great deal of our meetings is devoted to studying the level of agreement between our observed spectra and predicted spectra based on full simulation or clever techniques using the actual observed data to predict the background. In the case of the search for the Higgs boson, there are a couple dozen “channels” in which to search, which reflect how the Higgs is produced and how it decays. The results from these individual channels are then combined into one final statistical analysis which essentially answers the question: is there evidence of Higgs boson production if the Higgs masses thus-and-such a value? What will be presented next week at CERN is in fact the result of that analysis and as much detail as possible about the results feeding into the answer.

This year has seen a dramatic leap in our knowledge about where the Higgs boson isn’t, and as of a few weeks ago the combined results from CMS And ATLAS left open only a small mass window from 115–140 GeV where it could exist. As luck would have it, the remaining mass region is the most difficult to explore with the LHC, but it has been clear for some time that with the data set anticipated this year, and now recorded and analyzed, the LHC could close the window even further, and perhaps all the way after combining the results from both experiments and with the data from the Tevatron. But the window will only close completely if the Higgs is not there.

For a while, earlier this fall, there was rampant speculation in the science media about the possibility that “there is no Higgs boson” but as the allowed mass window has shrunk, it’s shrunk down right down to the region where we would expect the Higgs boson to exist, if it does. So we shouldn’t give up yet! We’ve known it will take a lot more data to establish the existence of the Higgs boson at the golden five sigma level and begin to measure its mass, etc., but by next summer I think the it should be clear one way or the other.

My own role in this whole process started years ago when I worked with my students and postdoc to create a new algorithms for identifying tau lepton decays (the tau is the heaviest partner of the electron), and helped develop new methods for calculating the Higgs boson mass from its decays to pairs of taus. By last year, before we had an appreciably large sample of physics data, we had established within the physics analysis groups the methods we wanted to deploy in this search. We teamed up with groups from other institutions and, a year ago, another professor (Sridhara Dasu from University of Wisconsin-Madison) and I led a team of about 10 students and postdocs in getting the first version of this analysis through the full process. It took months, but we eventually published the results in is a Physical Review Letter in the spring, as the LHC started to deliver much higher luminosity.

With new data in hand, we “turned the crank” on the same analysis, more or less, for the summer conferences adding a few embellishments, and then improved it again this fall. This pattern was repeated in parallel by a dozen other teams in the Higgs search. I would reckon there are at least 200 people involved in the search in a serious way in CMS. It’s been more of a marathon than a sprint for all concerned, and now my former student is now a postdoc at Wisconsin and my former postdoc is now a scientist at a Ecole Polytechnique in France. Our analysis group, I can tell you, has some of the most talented physicists with whom I’ve ever had the privilege to work. For me, that’s one of the great joys of being in this field: you are surrounded by really smart people.

It will be interesting to see how the media spin the results that emerge next week. Physicists still smart from the sting of an article in the New York Times back in 1992 with the title “300 Physicists Fail to Find Supersymmetry” and have become much more media-savvy.

If you believe the rumors, then perhaps a more apt metaphor is that of a tiny, growing new plant, two leaves reaching above the soil. With more water and light, it will grow. And grow. And grow.