To tell you what you need to know for the presentations on the Higgs particle search coming up on December 13th, I’m writing a sequence of three articles…
[OUT OF DATE: SEE THIS NEW POST]
Author: Matt Strassler
POSTED BY Matt Strassler
ON December 9, 2011
While I was on my way to Johns Hopkins University Monday evening, I wrote the following post, for publication today (Wednesday). Tuesday morning, CERN stole some of my thunder by putting out a press release consistent with the conclusion I drew below. Not that I mind. A quote from the press release follows this post.
The rumor mills on various blogs have been going berserk, with claims that a Higgs particle of Standard Model type (the simplest possible version of the Higgs particle) has been found by ATLAS and CMS (the two large general purpose experiments at the Large Hadron Collider.) The claims are that the Higgs signal is at a mass-energy [E=mc2] of 125 GeV; that CMS, in its search for a Higgs particle decaying to two photons, sees a small excess (that’s two or so standard deviations, or 2 σ, away from zero signal); and that ATLAS sees a larger excess (perhaps 3 σ) in their similar analysis. (You may find it useful to read my recent article about a lightweight Standard Model Higgs particle, and why searching for it through its decays to two photons is the best way to find it but takes frustratingly long — or you might like my recent guest post on Cosmic Variance about the Higgs search.)
Well, rumors are sometimes true, and this one might be, more or less.
- More precisely, it might be true that ATLAS and CMS see excesses of the claimed type and size. We’ll find out on December 13th.
- And also, it might even be true that these excesses are signs of the Standard Model Higgs particle. We will not find that out on December 13th.
Why not? There’s just not enough data yet. (more…)
POSTED BY Matt Strassler
ON December 7, 2011
I am visiting Johns Hopkins University in Baltimore today, giving a talk for experts on my recent Large Hadron Collider research (which I’ll describe sometime, if things with Higgs particles and speeding neutrinos ever calm down sufficiently!) But meanwhile I have written an article, concerning the search for the Higgs particle, which has appeared as a guest post on the Cosmic Variance blog today.
Many thanks to the pioneering science bloggers at Cosmic Variance, especially my colleague Sean Carroll, for the invitation to write for their deservedly famous blog!
I’ll have more to say about the Higgs-evidence rumors that are currently running around by tomorrow.
POSTED BY Matt Strassler
ON December 6, 2011
I’ve decided to write a new set of articles explaining why it takes time, potentially a long time, to discover the Higgs particle. First article is done: why even to find a Standard Model Higgs particle (the simplest possible type of Higgs particle that might be present in nature) has taken quite a while, if the Higgs particle is relatively lightweight. Coming soon: various exotic Higgs particles that would take several more years to discover.
If you’ve missed my two posts from the weekend you may want to read them:
- Saturday: The media is providing misleading reports on the Higgs particle search, not always properly distinguishing between the Standard Model Higgs particle (the simplest type of Higgs particle that might be present in nature) and Higgs particles in general. There’s a very big difference.
- Sunday: Although the search for the Standard Model Higgs particle is at least half over, it could take a very long time (as much as 10 years) to confirm that there are no Higgs particles of any type in nature.
I’m also recommending: (more…)
POSTED BY Matt Strassler
ON December 5, 2011
After yesterday’s post concerning the media reporting on the Higgs search, a lot of people have been asking me this: “Given that the Standard Model Higgs particle (the simplest possible Higgs particle) will be found or ruled out in the coming few months, why will it take as long as ten years to be sure nature sports no Higgs particle or particles of any type?” (more…)
POSTED BY Matt Strassler
ON December 4, 2011
As we approach the December 13 news conference to update the search for the Standard Model Higgs particle (the simplest possible Higgs particle) we are starting to see lots of news stories about it. And they’re all wonderfully misleading.
I love this quote from the BBC: “But there is an even more intriguing possibility: that [the Higgs particle] may not exist at all, at least in its simplest form.”
This is a lot like saying: “Maybe the earth has no trees at all, at least not maple trees.” Or “Maybe children on earth do not play games at all, at least not football.” Or “Maybe Picasso did not paint any pictures at all, at least not the Mona Lisa.”
If the simplest form of the Higgs particle does not exist in nature, that will surprise no one in the field. There are hundreds of serious scientific papers, written by experts over the past 40 years, suggesting other forms of the Higgs particle (or particles). Every novel idea (supersymmetry, extra dimensions, little Higgs, etc.) has a more complicated story than the Standard Model Higgs particle. Most particle physicists are hoping for precisely this situation. Exotic Higgs particles generally would take a little longer to find than the Standard Model version of the Higgs — but they’re still Higgs particles, just as oak trees are trees and basketball is a game.
We will not know if the Higgs particle does “not exist at all” for ten years. Let me say that again. It will take ten more years to sweep the floor clean and assure ourselves that there is no Higgs particle, of some exotic form, hidden in Large Hadron Collider data. See this post for more info.
So when I see a figure caption on a BBC article stating “the Higgs search is approaching its endgame at Cern”, all I can say is, “you’ve got to be kidding.” This is not the beginning of the end; it is the end of the beginning.
POSTED BY Matt Strassler
ON December 3, 2011
After a day and a half of intense discussions and exchanges of information, the Intensity Frontier workshop meeting is coming to an end today. I already mentioned on Wednesday that particle physicists are currently summarizing their efforts as roughly divided into three research directions:
- The Energy Frontier: Try to make new heavy particles or other high-energy phenomena using very high-energy high-collision-rate accelerators (such as the Large Hadron Collider)
- The Cosmic Frontier: Let the Universe itself, through its natural particle production mechanisms, teach us something (through properties of “dark energy” or dark matter or through cosmic rays, etc.)
- The Intensity Frontier: Search for rare new phenomena or difficult-to-produce new particles using medium-energy ultra-high-collision-rate accelerators, or some other low-energy ultra-high-rate mechanism.
Each frontier has its advantages; the energy frontier probes new particles and forces very directly, allowing for detailed study, whereas the intensity frontier is indirectly sensitive to much higher energies and/or much weaker forces, though it often provides fewer details. Meanwhile, at the cosmic frontier we rely purely upon what the universe has to offer, which has the obvious benefit that what the universe provides comes for free, and the disadvantage that what it provides is limited and out of our control. (more…)
POSTED BY Matt Strassler
ON December 2, 2011
Particle physicists in the United States, aiming to organize their thinking and make it easier to explain their views to each other and to the outside world, meet every few years in workshops to consider the future of the field. (Something like this is done in a number of other scientific fields as well.) Right now, particle physics is commonly described as pursuing three general research directions:
- The Energy Frontier: Try to make new heavy particles or other high-energy phenomena using very high-energy high-collision-rate accelerators (such as the Large Hadron Collider)
- The Cosmic Frontier: Let the Universe itself, through its natural particle production mechanisms, teach us something (through properties of “dark energy” or dark matter or through cosmic rays, etc.)
- The Intensity Frontier: Search for rare new phenomena or difficult-to-produce new particles using medium-energy ultra-high-collision-rate accelerators, or some other low-energy ultra-high-rate mechanism.
With the U.S. currently out of the business of the Energy Frontier (the Tevatron having closed and there being no plans for future accelerators here) the Department of Energy has recently asked the U.S. particle physics community to hold a large workshop on the Intensity Frontier, to bring its goals into focus.
A meeting associated with this effort is going on today through Friday, in Washington D.C. (more…)
POSTED BY Matt Strassler
ON November 30, 2011
Some of you may remember that a few months back there were widespread reports in the media — and various blog posts, including even ones by particle physicists such as University of California-Davis’s John Conway on Cosmic Variance — giving the impression that the 2011 summer’s results from the ATLAS and CMS experiments at the Large Hadron Collider (LHC) had all but ruled out a particular speculative idea called “supersymmetry”. (Here are links to my description of supersymmetry and the classic strategy people use to look for it, as well as the assumptions that underlie that strategy and what happens when you relax them.) I complained loudly back then that this was a terribly premature conclusion — that only the most popular version of supersymmetry had been excluded by the data at that time, and that there were still many types of searches that would need to be carried out before such a broad conclusion could be drawn. And I wasn’t the theoretical particle physicist to say so.
Well, a few months on, I’m glad to say that the experimentalists at ATLAS and CMS have collectively come to the conclusion that indeed there is a great deal of work left to do. This was reflected in several talks on supersymmetry searches at the HCP conference in Paris two weeks ago, including the final talk, given by Giacomo Polesello of ATLAS. (more…)
POSTED BY Matt Strassler
ON November 29, 2011
The principle of relativity comes up regularly in the context of space travel, and this week’s launch of NASA’s “Curiosity” rover mission was no exception. The BBC has a pretty nice article about it, but as happens so often in press articles, it stumbles in a big way at one point. Quoting from the article: “By the time the encapsulated rover was ejected on a path to the Red Planet, it was moving at 10 km/s (6 miles per second.)” Oh my heavens. 10 kilometers per second. That sounds very fast; highway speeds are 100 kilometers per hour. Unfortunately, the statement is completely meaningless.
In fact, right now, as you sit in your chair, reading this nice little article, you are moving at 30 kilometers per second. In a sense, anyway. Yet nobody is about to issue you a traffic ticket, or give you an award for traveling faster than a speeding bullet (less than a kilometer per second.)
Do you know that Einstein did not invent the principle of relativity? Click here to read on…
POSTED BY Matt Strassler
ON November 28, 2011
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