ATLAS Collaboration / CERN

This diagram shows the results of a proton-on-proton collision in the Large Hadron Collider's ATLAS detector last September, with four muons indicated by red tracks. Such a result could be consistent with the Standard Model with or without the Higgs boson, depending on the analysis of multiple events.

Has the Higgs boson finally been detected? It's almost gotten to the point that if a discovery of some sort doesn't come out of next week's update on the multibillion-dollar subatomic search, it'll be a big surprise. But how far will the announcement go, and what will it mean for the future of physics?

To refresh your memory, the Higgs boson is the only fundamental subatomic particle predicted by theory but not yet detected. It's thought to play a role in endowing some particles, such as the W and Z boson, with mass ... while leaving other particles, such as the photon, massless. The Higgs mechanism, proposed by British physicist Peter Higgs and others in the 1960s, could have played a role in electroweak symmetry breaking, which was a key event in the rise of the universe as we know it.

The Higgs boson is so key to the current understanding of fundamental physics that Nobel-winning scientist Leon Lederman nicknamed it the "God Particle" — a term that has been making other physicists wince ever since. Another religion-tinged cliche would be to call it the "holy grail of particle physics," as CERN physicist John Ellis has. He says finding the Higgs is a key goal for the $10 billion Large Hadron Collider.

"That's one thing that we're really looking forward to with the LHC," Ellis told me five years ago. "In fact, back when we persuaded the politicians to stump up the money to build the thing, that's probably what we told them."

Last December, the teams reported that they saw "tantalizing hints" of the Higgs' existence at a mass of around 125 billion electron volts, or 125 GeV. But the confidence in those results was not yet high enough to claim a discovery. Now the teams behind the collider's CMS and ATLAS experiments have collected higher piles of data, at higher energy levels, sparking higher expectations.

The 5-sigma fetish
When physicists talk about their confidence, they talk in terms of statistical "sigma" levels. The higher the sigma, the less likely that the results are just a fluke. In particle physics, 3 sigma constitutes strong evidence, but it takes 5 sigma to accept the results as a discovery. At the 5-sigma level, statisticians say there's roughly one chance out of 3 million that you're leaping to the wrong conclusion, as opposed to a 1-in-1,000 chance at the 3-sigma level. That distinction makes a big difference when you're sifting through billions upon billions of proton-on-proton collision reports.

Last year, the best that the LHC teams could do was 3.6 sigma for ATLAS, and 2.6 for CMS. Now physicists are looking for a 5.

For three weeks, the teams have been running the numbers on their experimental results in secret, so as to avoid any chance that one analysis will influence the other. Their results are to be announced during a presentation at the CERN nuclear research center in Geneva, which will be webcast starting at 9 a.m. CEST (3 a.m. ET) on July 4. Although no official word has leaked out, the unofficial word is that someone looking for a discovery could get to the magic number.

"Reports from the experiments indicate that at least one of them, if not both, will reach the 5 sigma level of significance for the Higgs signal, when they combine 2011 and 2012 data and the most sensitive channel. So, this will definitely be the long-awaited Higgs discovery announcement, and party time for HEP [high-energy physics] physicists," Columbia mathematician Peter Woit wrote on his Not Even Wrong blog a week ago.

Since then, other physicist-bloggers have been fine-tuning the expectations. Here's a selection:

• On the Resonaances blog, physicist Adam Falkowski (a.k.a. Jester) has a countdown clock ticking toward the Higgs discovery. "It is not clear, at least to me, if either of the two experiments will pass the 5-sigma fetish. But it does not really matter. ... What's going to change next Wednesday is that the status of the Higgs will be upgraded from 'almost certain' to 'beyond reasonable doubt.'"
• On Quantum Diaries, Southern Methodist University physicist Aidan Randle-Conde advises against trying to combine the data from the two teams to get to 5 sigma. "With all this pressure to get as much out of the data as possible, it's tempting to move too quickly and do what we can to get a discovery, but now is not the time to rush things," he writes.
• On the ViXra Log, Philip Gibbs says that when CERN's researchers report their progress, "it is likely that the main question they are investigating will switch from 'Is there a Higgs Boson?' to 'Is it the Standard Model Higgs boson?'"
• On a blog titled "Of Particular Significance," Rutgers physicist Matt Strassler advises caution, but also suggests getting "the cases of champagne ready, in case the time has finally come to pop the corks." He points out that a discovery announcement would by no means be the end of the story. "Even if we see strong evidence of a Higgs-like particle ... the correct understanding of that particle — in particular, determining whether it is or isn't a 'simplest Higgs' — may take years."
• As we approach H-Hour, you can expect to hear more via all these outlets as well as other blogs such as Cosmic Variance and "A Quantum Diaries Survivor."

Hedging on the Higgs
What Strassler and Gibbs are saying is important: Technically speaking, CERN is unlikely to announce that the Higgs boson has been definitively discovered. It's more likely that physicists will talk about a new particle that has a signature consistent with the Higgs but has to be investigated further.

CERN hinted at that approach last week in the news release announcing Wednesday's webcast. "It's a bit like spotting a familiar face from afar," said the center's 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."

Gigi Rolandi, a senior research physicist at CERN, used a similar analogy in a video released this week, referring to crops of corn (which he calls maize, as most Europeans do), wheat (which he calls corn) and poppy flowers. Some particles are as easy to spot as a red poppy in a wheat field, he said. But not the Higgs. "The search for the Higgs is more similar to looking for a single plant of maize among many, many corn plants, than looking for a poppy among the corn," he said.

We'll get a foretaste of Wednesday's proceedings on Monday, when Fermilab is due to provide its final update on the Higgs boson search, based on the full set of data from the now-closed Tevatron. Will Fermilab try to steal some of CERN's thunder, at least for a couple of days? Stay tuned....

Update for 12:05 p.m. ET June 30: Some commenters are asking whether there are practical applications for the discoveries that could be made at the Large Hadron Collider. I addressed that question in a story I wrote four years ago, headlined "Discovery or Doom? Collider Stirs Debate." Please check out the article, as well as the Flash interactive on "Nightmares and Dreams" at the LHC.

Update for 6 p.m. ET July 1: To watch streaming video of the Fermilab Higgs update at 9 a.m. CT (10 a.m. ET) Monday, click through to this Web link.

The buzz leading uo to H-Hour is getting even louder, as expected. The Daily Mail reports that some of the theorists behind the Higgs boson concept have been invited to the CERN briefing on Wednesday, which some observers see as another sign that something definitive will be announced. Also, Reuters' Robert Evans keeps the buzz humming in a dispatch published today.

Previous episodes in the Higgs hunt:

• Ups and downs for Higgs boson buzz
• Cartoons visualize the Higgs boson
• Can physicists crack the big puzzle?
• Flash graphic: Inside the Big Bang Machine
• Flash graphic: Michio Kaku on LHC nightmares and dreams
• Msnbc.com's special report on the Large Hadron Collider

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

CERN / CMS Collaboration

A computer graphic shows a typical Higgs boson candidate event, including two high-energy photons whose energy (depicted by red towers) is measured in the Compact Muon Solenoid's electromagnetic calorimeter. The yellow lines are the measured tracks of other particles produced in the collision. The pale blue volume represents the CMS' crystal calorimeter barrel.

A week ago, sources started passing the word that physicists were "fired up" about further evidence for the existence of the Higgs boson, the last undiscovered particle predicted by the Standard Model and the main quarry for the $10 billion Large Hadron Collider.

That blaze of buzz reached a high point this week, when Columbia mathematician Peter Woit reported "reliable rumors" that the confidence level for a detection of the Higgs' signature in the mass range of around 125 billion electron-volts, or 125 GeV, was increasing.

"CERN will soon have to decide how to spin this: will they announce discovery of the Higgs, or will they wait for some overwhelmingly convincing standard to be met, such as 5 sigma in at least one channel of one experiment?" Woit wrote.

"Sigma" refers to the statistical confidence that a given result is more than a fluke, with 5 sigma serving as the gold standard for a discovery. If you're a Higgs-watcher, you'll be hearing a lot about sigma in the next couple of weeks, leading up to the International Conference on High-Energy Physics, or ICHEP, in Australia from July 4 to 11. That's when the LHC's teams are due to provide a status report on the search for the Higgs. 

The Higgs hunt is hot because physicists have hypothesized about the boson for 40 years as part of the mechanism by which some particles acquire mass while others don't. The Higgs is so fundamental to the frontier of physics that Fermilab's Leon Lederman once called it the "God Particle" — a term that most other physicists positively hate. Finding it in the mass range where it's expected to be would serve as solid confirmation for the Standard Model, one of the most successful theories in the history of science. Not finding it would be more interesting: Physicists would have to consider some other mechanism, outside the Standard Model, to explain particle mass. And there's nothing theorists love more than a challenge like that.

In December, the teams behind the ATLAS and CMS detectors reported "tantalizing hints" of a Higgs detection at 125 GeV, with confidence levels of 3.6 sigma for ATLAS and 2.6 sigma for CMS. If the additional observations made since then show the same sorts of hints, those sigma levels should go up — and that's been the gist of the buzz over the last week or so. For science geeks, that's a big deal, or at least a big meme: so big that the hashtag #HiggsRumors was for a time on top of Twitter's trending list, Discovery News' Jennifer Ouelette noted.

A lot of that trending took place because of the in-jokes spawned by the original buzz — which has now fallen to a steady hum, thanks to a string of reality checks.

"Please do not believe the blogs," ATLAS spokeswoman Fabiola Gianotti told The New York Times. "I am very surprised that rumors appear on a subject that is really evolving daily," CMS spokesman Guido Tonelli told Science News. "The experimenters can't possibly have their data in presentable form yet, so the rumors can't be correct in every detail," Rutgers theoretical physicist Matt Strassler observed on his blog.

Union College physicist Chad Orzel, the author of "How to Teach Relativity to Your Dog," said the celebrity-level hype was "the price of success":

"I mean, it’s not an accident that there’s a lot of excitement about the maybe-sorta-kinda discovery of the Higgs. This is the product of years of relentless hype from the particle physics community. They've been talking about this goddamn particle for longer than I've been running this blog, and it's finally percolated out into the general public consciousness enough that buzz about it can trend on Twitter. Complaining that your persistent effort to get people to care about particle physics esoterica has led to people being excited about particle physics esoterica seems more than a little churlish.

"So, lighten up. Revel in the success of your hype machine. God knows, if there were a Twitter trending topic about Bose-Einstein Condensation or anything else in atomic physics, I’d do the Happy Dance all the way down the hall. You’ve worked hard to make your elusive particle a celebrity, now reap the rewards."

The true reaping will come in a couple of weeks. As Reuters' Robert Evans reported, the most recent readings from ATLAS and CMS are being analyzed in isolation, so that one team's conclusions don't influence the other team. Until the ICHEP actually takes place, hype is just about all we'll hear about. But in the meantime, get ready for the real news by reviewing these resources:

• Higgs vs. hype: A mini-guide
• Cartoons visualize the Higgs boson
• What's a boson? Tour the particle zoo
• Special report on the Large Hadron Collider
• Search msnbc.com for the Higgs boson

Update for 1 p.m. ET June 22: Europe's CERN particle-physics center just announced that the big update on the Higgs search will come on July 4, during a seminar at 3 a.m. ET that's tied to the start of the ICHEP conference. 

"We now have more than double the data we had last year," CERN's director for research and computing, Sergio Bertolucci, was quoted as saying. "That should be enough to see whether the trends we were seeing in the 2011 data are still there, or whether they’ve gone away. It’s a very exciting time."

CERN said that if a new particle is discovered, the ATLAS and CMS teams will need more time to ascertain whether it's the Higgs.

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

CERN said physicists at the conference in Melbourne will be able to join the seminar via a live two-way link. The seminar will be followed by a news conference at CERN. There'll be a webcast available via http://webcast.cern.ch. Stay tuned...

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

The prime target for the $10 billion Large Hadron Collider is discovery and study of the Higgs boson — but what the heck is the Higgs, and what's it supposed to do? PHD Comics' Jorge Cham explains the quest in an animated cartoon that draws upon the expertise of Daniel Whiteson, a particle physicist from the University of California at Irvine who's working at Europe's CERN research center.

The Higgs boson, sometimes referred to as the "God Particle," is thought to be the force-carrier for a field that endows subatomic particles with varying values of mass. British physicist Peter Higgs and others theorized that it must exist to fill out a gap in physics' Standard Model of particle physics, but it hasn't yet been detected. Scientists expect it to turn up at the LHC, or else they might have to go back to the drawing boards and rework the Standard Model.

Almost two decades ago, Britain's science minister challenged experts to come up with an everyday explanation for the way the Higgs worked, and physicist David Miller came up with a comparison to Margaret Thatcher making her way through a crowded cocktail party. Whiteson and Cham use the analogy of marbles rolling across a floor, which works, too. Check out the big-format animated version on the PHD Comics Web site or on Vimeo.

If physicists at the LHC get their way, the discussion of the Higgs boson could get a lot less theoretical by the end of this year, thanks to the increase in power levels and data return from the LHC and its particle detectors. However, Nature's Geoff Brumfiel reports today that the readings from hundreds of trillions of collisions are piling up so fast that the computers are having a hard time keeping up with the analysis. He writes that all those collisions are growing into a "thick fog" that threatens to obscure the signature of the elusive Higgs. Researchers are using clever computational techniques to separate the wheat from the chaff, data-wise, and are prepared to dial back the collision rate if necessary.

If it sounds as if the physicists have it rough, just imagine how the particles must feel. That's exactly what animator Karen Cheung, Oxford physicist Alan Barr and their colleagues did in a cartoon that was created for the Oxford Sparks Web portal. Enjoy!

More about the Higgs and the LHC:

• Higgs vs. hype: A mini-guide
• Can physicists crack the big puzzle?
• Flash graphic: Inside the Big Bang Machine
• Flash graphic: Michio Kaku on LHC nightmares and dreams
• Msnbc.com's special report on the Large Hadron Collider

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Updated 9:50 a.m. ET Dec. 13:

Physicists have revealed what they've found so far in their quest for the Higgs boson at Europe's Large Hadron Collider on Tuesday, after days of buildup that put the "God particle" on a par with Obi-Wan Kenobi and the Force. But the Higgs boson isn't a religious experience, and it won't help you destroy the Death Star. So what is the Higgs? And what do scientists know about it? Here's a small guide to the Large Hadron Collider's latest:

Why it's important: For decades, physicists have used a theory known as the Standard Model to explain the interactions of subatomic particles, and the theory works beautifully. It's guided our way through the world of nuclear power, television, microwave ovens and lasers. One problem: The theory needed something extra to explain why some particles have mass and some don't. Back in the 1960s, physicist Peter Higgs and his colleagues proposed the existence of a mysterious energy field that interacts with some particles more than others, resulting in varying values for particle mass. That field is known as the Higgs field, and it's associated with a particle called the Higgs boson.

Today, the Higgs boson is the last fundamental piece missing from the Standard Model. Finding it is the most commonly cited reason for building the $10 billion LHC. If the characteristics of the Higgs particle (or particles) match what's predicted by the current formulation of the Standard Model, that would bring a sense of completion to particle physics. If the Higgs isn't found, that might force physicists to tweak or even discard the Standard Model. "I find it difficult to imagine how the theory works without it," Peter Higgs recently told the London monthly Prospect. If a non-Standard Higgs is detected, that could totally change the way we see the universe. In the far future, we might even find a way to take advantage of the Higgs field, just as earlier physicists took advantage of the electromagnetic field, radioactivity or quantum effects.

Where they're at: The quest for the Higgs is being conducted using two detectors at the LHC, which is housed at Europe's CERN particle physics center on the French-Swiss border. The collider has been built inside a 17-mile-round (27-kilometer-round) underground tunnel where two beams of protons are smashed together at 99.999999 percent of the speed of light.

The detectors, known as ATLAS (A Toroidal LHC ApparatuS) and CMS (Compact Muon Solenoid), are placed at key points on the collider ring. They're built somewhat differently, and they serve as a system of checks and balances to make sure one team can confirm what the other team is seeing. The LHC is the only collider on earth that can achieve the energies required to probe the Higgs boson's potential hiding places. (However, higher energies have been observed in cosmic ray collisions high above Earth's surface.)

CERN

This graphic shows a typical candidate event in the search for the Higgs boson, including two high-energy photons whose energy (depicted by red towers) has been measured in the CMS electromagnetic calorimeter. The yellow lines are the measured tracks of other particles produced in the collision.

What they've learned: The ATLAS and CMS teams shared their results in a series of public presentations at CERN, beginning at 8 a.m. ET Tuesday. Aidan Randle-Condle has been liveblogging the event at the Quantum Diaries blog. You'll find a less geeky liveblog at The Guardian. Canada's Perimeter Institute for Theoretical Physics is presenting a webcast discussion after the announcement, at 12:30 p.m. ET.

Here are the key numbers: The CMS team said that if it exists, the Higgs boson would have to have a mass somewhere between 115 billion and 127 electron volts (that's 115-127 GeV for short). ATLAS reported a range of 116-130 GeV. Both teams saw "tantalizing hints" of a detection around the 124-125 GeV level, but nothing that could yet be called a discovery. That's because the confidence values are no higher than 3.6 sigma for ATLAS, and 2.6 sigma for CMS.

Wait ... what's a sigma? Those numbers measure how likely it is that the effect seen amid the billions of collisions at the LHC is real rather than a statistical fluke. Suppose you have a machine that flips coins to check whether they've been stamped correctly with heads and tails, rather than two heads. You have to decide when to stop the conveyor belt to remove a coin with two heads, based purely on the machine's report. If the machine flips five heads in a row, you have more than 2 sigma confidence that there are heads on both sides of the coin. If it flips 10 heads in a row, the confidence goes up to more than 3 sigma. If it flips 20 heads in a row, you have a 5-sigma observation. (You could just have someone look at both sides of the coin, but you get the idea.)

In scientific observations, a level of 3 sigma constitutes "evidence" that an observed effect is real, and not just a fluke. You have to go up to 5 sigma to declare a "discovery." Thus, the observations hint at where the Higgs boson might be found, but this can't yet be called a discovery. In its news release, CERN used a different analogy to describe the confidence level, using dice rather than coins: "Taken individually, none of these excesses is any more statistically significant than rolling a die and coming up with two sixes in a row."

What's next? However the results are spun, more data will be required to nail down a confirmed detection of the Higgs. The proton beams have been shut down for CERN's holiday break, but they'll be started up again next year. The results so far have raised hopes that confirmation of the Higgs' existence (or its non-existence) will come by the end of 2012. After next year's round of experiments, the LHC will be shut down until 2014 for a major upgrade. It won't ramp up to its full power of 7 trillion electron volts per beam until after the upgrade. There'll be a long wait to get to the deepest mysteries of particle physics — but based on the latest results, there's renewed hope for the Higgs.

More on the Higgs boson and the LHC:

• Collider's new data will narrow Higgs search
• Can physicists crack the big puzzle?
• Tales of the big bang at the LHC
• What's a boson? Tour the particle zoo
• Special report on the Big Bang Machine
• Search msnbc.com for the Higgs boson

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.