Higgs

A couple of us are going to try to live-blog the July 4 Higgs update seminars from CERN. This effort will be subject to the whims of internet connectivity, of course, but we’ll do our best. At the moment we have correspondents on at least three different continents (I [Sean] am at CERN, JoAnne is in Melbourne for ICHEP, and I think John is in California…), so hopefully at least one of us will be able to get through. We’ll just be updating this post, so keep refreshing. You are also welcome to try the CERN webcast.

Seminars proper start at 9am Geneva time (3am Eastern time, midnight Pacific time, 5pm Melbourne time). One from ATLAS, by Fabiola Giannoti, and one from CMS, by Joe Incandela. Then a press conference after. Remember what we’re looking for: how significant is the signal, do the two experiments agree with each other, does the rate agree with the Standard Model prediction, are different channels mutually consistent with each other.

If people ask questions in the comments there is some chance that we will try to answer them.

Has there ever been a scientific discovery (if indeed we will be able to call it that) that has been anticipated so far ahead of time? Can’t think of any off the top of my head. Fasten your seatbelts!

11:38 pm Geneva time (Sean): Preliminary thought #1: There is a “nightmare scenario” that particle physicists have worried about for years. Namely: find exactly the Standard Model Higgs and nothing else at the LHC. I personally assign the nightmare scenario very low probability. Not on the basis of any inside info, just on the basis of physics. We know the Standard Model is not right; there is dark matter, there is dark energy, there is baryogenesis, there are the hierarchy and cosmological constant and strong-CP problems. It can’t be the final answer. Seems to me much more likely that there is interesting physics at the weak scale above and beyond the Higgs, than we just get stuck with a vanilla Standard Model. Beyond this physics-informed prediction, there is the wishful hope that the Higgs itself leads directly to new physics. Most obvious example: in many (most?) models of dark matter as weakly-interacting massive particles, the dominant way that dark matter and ordinary matter interact is through exchange of Higgs bosons. If that’s how nature works, the Higgs is literally a portal from our world to another. This isn’t the end of the show, it’s merely an act break (as we say in the movie biz).

11:44 pm Geneva time (Sean): Preliminary thought #2: I am a mere theorist, and let me be as legitimately humble as I can be right here. Beyond the details of whatever may or may not be found, the LHC is a gargantuan effort undertaken by literally thousands of people over the course of years and in many cases decades. This moment, we hope, is something of a payoff for their perseverance. My hat is off to the experimentalists and engineers and technicians who really made it happen.

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Live-Blogging the Higgs SeminarRead More »

Update: There’s a slightly expanded version of this post on the NOVA website, where I fill in some background on what the Higgs is and why we care.

Greetings from Geneva, where I’m visiting CERN to attend the much-anticipated Higgs update seminars on Wednesday, July 4. We’re all wondering whether they will say the magic words “We’ve discovered the Higgs,” but there’s more detailed information to watch out for. Hoping for some good book fodder, at the very least. (I personally am not hunting for Higgses, any more than someone who eats at a seafood restaurant has “gone fishing,” but you know what I mean.) Remember Higgs 101, and why we need it.

If at all possible, I’ll try to live-blog here at CV during the seminars. They will start at 9am Geneva time, a slot chosen to enable a simulcast in Melbourne for people attending the ICHEP Conference. For folks in the U.S., not so convenient: it’s 3am Eastern time, Midnight (July 3/4) Pacific time. Here is the seminar announcement, and of course CERN will have a live webcast. Or try to, anyway; last time something like this was arranged, back in December, the live feed collapsed pretty quickly under the load. I’m sure I won’t be the only one live-blogging: here’s Aidan Randle-Conde and Tommaso Dorigo.

So what are we looking for? …

Hunting for HiggsesRead More »

That is to say, CERN is going to share with us what the most recent LHC data are saying about the Higgs (and whatever else might have popped up, I guess) in a seminar on July 4th at CERN itself, just before the ICHEP conference in Melbourne. Excerpt from the press release:

If and when a new particle is discovered, ATLAS and CMS will need time to ascertain whether it is the long sought Higgs boson, the last missing ingredient of the Standard Model of particle physics, or whether it is a more exotic form of the boson that could open the door to new physics.

“It’s a bit like spotting a familiar face from afar,” said CERN Director General Rolf Heuer, “sometimes you need closer inspection to find out whether it’s really your best friend, or actually your best friend’s twin.”

Suggestive.

There’s been a lot of talking back and forth about the ethics of trafficking in rumors, and I don’t mean the jokey kind. Personally I think it’s pretty simple: if a collaboration of thousands of physicists wants to keep their results quiet until they are ready to announce them, that’s completely their right. I’m not going to pass along anonymous tips — if the tippers didn’t understand that they were doing something wrong, they wouldn’t stay anonymous. The rumors aren’t part of keeping the public informed; there’s plenty of time for that once the actual results are released.

Which will happen very soon! Whatever the answers may be, it’s a great accomplishment for the LHC folks to have come this far.

The Large Hadron Collider has been humming along this year, collecting about 5 inverse femtobarns of data, similar to what they had all last year, at a slightly higher energy (8 TeV vs. 7 TeV). Of course last year we were treated to tantalizing hints of a Higgs boson with a mass of about 125 GeV, so it’s natural to ask whether that evidence has been continuing to accumulate. Answers should be forthcoming early in July at the International Conference on High Energy Physics in Melbourne, where talks are scheduled from both CMS and ATLAS.

I believe, given the short time available, that each collaboration can update us on the results from this year’s run thus far, but it will probably take longer to combine the results from the two experiments, as well as combining with last year’s data. (Combining results sounds straightforward, but is actually extremely subtle, due to separate kinds of systematic effects for the different experiments, or even the same experiment at different energies.) Presumably that means that we can accumulate new evidence for the Higgs, but it would be surprising if they were actually able to announce a discovery. I’m also told that the analysis of this year’s data thus far has been “blind” — i.e., they add a secret offset to the real data so that all of the reduction and background subtraction can be carried out without bias, and only then do they “open the box” and see what the actual data are saying. If this is true, literally nobody in the world knows right now what the LHC has actually been seeing, as far as the Higgs is concerned. But we’ll find out before too long.