Thursday, July 5, 2012

Nearly-discovered Higgs boson: great news

Brian Greene's summary of the CERN announcement in the

confirming the likely existence of the Higgs boson is immediately  below.  I have added images.

bg bw

Following, there is a more complete explanation from Science News, including information I did no know.  For example, I did not know that the Higgs appears at the temperature when the electroweak symmetry breaks.  The Higgs is worth some effort to catch its outline. Ir is hard to see it's relevance for South Yemen.

Here is Brian Greene, my choice for president, or for anything else he wants, so high is my respect for him.

Brian Greene Reacts to Today’s CERN Announcement
Earlier this morning, CERN made a much-anticipated announcement about its progress in finding the elusive Higgs particle. Below, Brian Greene explains the significance of the news.

Here’s a summary of today’s announcement: The Large Hadron Collider (a 17-mile-long circular tunnel in which protons are sent whizzing around in opposite directions at just shy of light-speed,

and directed into head-on collisions) has two mammoth detectors called ATLAS and CMS (each of which captures and analyzes particulate debris created by the proton–proton collisions). Two independent (and highly competitive) research teams, involving thousands of scientists, using each of these detectors have seen moderately convincing evidence that the elusive Higgs particle has been created in some of the proton–proton collisions.
This is a challenging experiment as the detectors can’t see the Higgs particle directly—it is a short-lived particle that quickly falls apart (decays)—but, rather, they infer its presence by seeing its decay products.

(Watch here, as physicist and ATLAS researcher Monica Dunford explains this process of inferring new possible particles during the World Science Festival.)

In particular, the equations show that when a Higgs particle decays, some fraction of the time two photons (particles of light) are produced. The researchers sift through a maelstrom of debris for these photons, but even then they need to ensure that the photons weren’t produced by some other, more mundane process.  This painstaking work, aided by sophisticated computer analysis,

now shows evidence of a Higgs particle that weighs about 126 times as much as a proton.
The researchers’ confidence in this result, while fairly strong, does not yet rise to the level at which a definitive discovery is claimed (there’s roughly a chance of a few in a thousand that the data is a statistical fluke, sort of like the chance of getting 8 to 9 heads in a row when you flip a coin;

 I'm not convinced.  And because I'm not convinced, there's only one way to decide this.  I'm flipping a coin.  Spain is heads and Netherlands is tails.  My decision rubric is this: 
The Spanish are heads because Puyol scored a header goal to put them into the finals. 
The protocol for claiming a definitive discovery is more like 1 in a million, similar to getting heads about 20 times in a row). But within the next few months, or surely within the next year, the teams should know whether or not they’ve found the Higgs particle.

For some background, here’s a short piece (about a minute long) I filmed giving an explanation of the Higgs idea—take a look if you have a moment. In the video, when I refer to a “molasses-like substance” that’s a metaphor for the “Higgs field”; the Higgs particle would be a tiny nugget of that field which the violent particle collisions at the Large Hadron Collider may have, roughly speaking, knocked loose.

 Here are exerts from the New York Times announcement of the almost-discovery:

The New York Times

July 4, 2012
Physicists Find Elusive Particle Seen as Key to Universe
ASPEN, Colo. — Signaling a likely end to one of the longest, most expensive searches in the history of science, physicists said Wednesday that they had discovered a new subatomic particle that looks for all the world like the Higgs boson, a key to understanding why there is diversity and life in the universe.

Like Omar Sharif

materializing out of the shimmering desert as a man on a camel in “Lawrence of Arabia,”

the elusive boson has been coming slowly into view since last winter, as the first signals of its existence grew until they practically jumped off the chart.

“I think we have it,” said Rolf-Dieter Heuer, the director general of CERN, the multinational research center headquartered in Geneva. The agency is home to the Large Hadron Collider, the immense particle accelerator that produced the new data by colliding protons. The findings were announced by two separate teams. Dr. Heuer called the discovery “a historic milestone.”

He and others said that it was too soon to know for sure, however, whether the new particle is the one predicted by the Standard Model, the theory that has ruled physics for the last half-century. The particle is predicted to imbue elementary particles with mass. It may be an impostor as yet unknown to physics, perhaps the first of many particles yet to be discovered.

That possibility is particularly exciting to physicists, as it could point the way to new, deeper ideas, beyond the Standard Model, about the nature of reality.
For now, some physicists are simply calling it a “Higgslike” particle.
“It’s something that may, in the end, be one of the biggest observations of any new phenomena in our field in the last 30 or 40 years,” said Joe Incandela, a physicist of the University of California, Santa Barbara, and a spokesman for one of the two groups reporting new data on Wednesday.
Here at the Aspen Center for Physics, a retreat for scientists, bleary-eyed physicists drank Champagne in the wee hours as word arrived via Webcast from CERN.
It was a scene duplicated in Melbourne, Australia, where physicists had gathered for a major conference, as well as in Los Angeles, Chicago, Princeton, New York, London and beyond — everywhere that members of a curious species have dedicated their lives and fortunes to the search for their origins in a dark universe.
In Geneva, 1,000 people stood in line all night to get into an auditorium at CERN, where some attendees noted a rock-concert ambience.
 Peter Higgs, the University of Edinburgh theorist for whom the boson is named, entered the meeting to a sustained ovation.
Here's Peter Higgs in the 1960s, when he and others
 first proposed the idea of a "field" that would explain particle mass 
Confirmation of the Higgs boson or something very much like it would constitute a rendezvous with destiny for a generation of physicists who have believed in the boson for half a century without ever seeing it. The finding affirms a grand view of a universe described by simple and elegant and symmetrical laws — but one in which everything interesting, like ourselves, results from flaws or breaks in that symmetry.
According to the Standard Model, the Higgs boson is the only manifestation of an invisible force field, a cosmic molasses that permeates space and imbues elementary particles with mass. Particles wading through the field gain heft the way a bill going through Congress attracts riders and amendments, becoming ever more ponderous.
Without the Higgs field, as it is known, or something like it, all elementary forms of matter would zoom around at the speed of light, flowing through our hands like moonlight. There would be neither atoms nor life.
Physicists said that they would probably be studying the new particle for years. Any deviations from the simplest version predicted by current theory — and there are hints of some already — could begin to answer questions left hanging by the Standard Model. For example, what is the dark matter that provides the gravitational scaffolding of galaxies?
And why is the universe made of matter instead of antimatter?
“If the boson really is not acting standard, then that will imply that there is more to the story — more particles, maybe more forces around the corner,” Neal Weiner, a theorist at New York University, wrote in an e-mail. “What that would be is anyone’s guess at the moment.”
Wednesday’s announcement was also an impressive opening act for the Large Hadron Collider, the world’s biggest physics machine, which cost $10 billion to build and began operating only two years ago. It is still running at only half-power.
Physicists had been icing the Champagne ever since last December. Two teams of about 3,000 physicists each — one named Atlas, led by Fabiola Gianotti, and the other CMS, led by Dr. Incandela — operate giant detectors in the collider, sorting the debris from the primordial fireballs left after proton collisions.
Last winter, they both reported hints of the same particle. They were not able, however, to rule out the possibility that it was a statistical fluke. Since then, the collider has more than doubled the number of collisions it has recorded.
The results announced Wednesday capped two weeks of feverish speculation and Internet buzz as the physicists, who had been sworn to secrecy, did a breakneck analysis of about 800 trillion proton-proton collisions over the last two years.
•    •   •
Gerald Guralnik, one of the founders of the Higgs theory, said he was glad to be at a physics meeting “where there is applause, like a football game.”
Asked to comment after the announcements, Dr. Higgs seemed overwhelmed. “For me, it’s really an incredible thing that’s happened in my lifetime,” he said.
One implication of their theory was that this cosmic molasses, normally invisible, would produce its own quantum particle if hit hard enough with the right amount of energy. The particle would be fragile and fall apart within a millionth of a second in a dozen possible ways, depending upon its own mass.
••  •  •
Finding the missing boson was one of the main goals of the Large Hadron Collider. Both Dr. Heuer and Dr. Gianotti said they had not expected the search to succeed so quickly.
•    •   •
So far, the physicists admit, they know little about their new boson. The CERN results are mostly based on measurements of two or three of the dozen different ways, or “channels,” by which a Higgs boson could be produced and then decay.
There are hints, but only hints so far, that some of the channels are overproducing the boson while others might be underproducing it, clues that maybe there is more at work here than the Standard Model would predict.
“This could be the first in a ring of discoveries,” said Guido Tonelli of CERN.
In an e-mail, Maria Spiropulu, a professor at the California Institute of Technology who works with the CMS team of physicists, said: “I personally do not want it to be standard model anything — I don’t want it to be simple or symmetric or as predicted. I want us all to have been dealt a complex hand that will send me (and all of us) in a (good) loop for a long time.”
Nima Arkani-Hamed, a physicist at the Institute for Advanced Study in Princeton, said: “It’s a triumphant day for fundamental physics. Now some fun begins.”
 ScienceNews  July 4, 2012

Essay: Nature's secrets foretold
Higgs discovery celebrates math's power to make predictions about the real world
Web edition : Wednesday, July 4th, 2012

By now, all aficionados of physics news — and quite a few people who don’t know physics from phonics — have heard about the discovery of the Higgs boson. It’s the biggest news in physics ever tweeted. And it came after a long wait. For more than three decades, the Higgs has been physicists’ version of King Arthur’s Holy Grail, Ponce de Leon’s Fountain of Youth, Captain Ahab’s Moby Dick. It’s been an obsession, a fixation, an addiction to an idea that almost every expert believed just had to be true.
But despite years of searching, using the most complex machines ever built on the planet, the Higgs remained as elusive as a World Series ring for a Chicago Cub. Until now. Physicists at the Large Hadron Collider have finally established the existence of a new particle, weighing in at a mass of about 11 dozen protons. Although the official announcement of the new particle was cautiously worded, everybody assumes it’s the Higgs.
Asked why the Higgs boson is so important, most physicists reflexively respond that it’s a piece of the cosmic substance that endows elementary particles with mass. That perhaps, to some, sounds a bit underwhelming — just another culprit to blame for the obesity epidemic. But the Higgs’ importance should be expressed more dramatically.
"We're reaching into the fabric of the universe at a level we've never done before," says Joe Incandela, a physicist at the University of California, Santa Barbara and spokesperson for one of the experimental teams reporting the discovery. "This is telling us something that's a key to the structure of the universe."
In fact, the Higgs is responsible for the structure of the universe as we know it. It's the Higgs that makes physical reality the way it is, with atoms, chemical reactions and life. No Higgs, no molecules. No planets. No people.
Strictly speaking, it’s better to say that without the Higgs, something even more exotic would have to do its job. That job, in physics speak, is “electroweak symmetry breaking.” In the universe’s earliest picoseconds, electro­magnetism was a component of a more primordial “electroweak” force, incorporating what’s now called the weak force (known for its role in radioactivity). Equations describing the electroweak force are symmetric — that is, they describe electromagnetism and the weak force as equals. But somehow, the weak force split from electro­magnetism. In other words, this mathematical symmetry between electro- and weak forces was “broken.”
Symmetry in nature’s laws is not optional; it ensures that the laws work the same for everybody, no matter where they are or how they move. But real life can get messy if something disrupts the symmetry. That’s what the Higgs does: It puts the universe on course to create reality’s complexities.
“In seeking the agent of electroweak symmetry breaking, we hope to learn why the everyday world is as we find it: why atoms, chemistry, and stable structures can exist,” writes theoretical physicist Chris Quigg of Fermilab.
Mathematically, the Higgs boson is a consequence of equations describing a field of force, the Higgs field. Visually, it’s not so easy to describe. Like the magnetic field around a magnet, the Higgs field exerts its influence without being visible.
Also like a magnetic field, the Higgs field’s strength falls to zero when the temperature is too high. (Heat an iron bar magnet above 770° Celsius, and the magnetism vanishes.) So at the birth of the universe in the Big Bang, when temperatures exceeded a million billion trillion degrees, the Higgs field did not distinguish itself. It and everything else that the universe was destined to contain existed within an undifferentiated primordial fireball of explosive energy.
You could think of the infant cosmos as a huge container of hot steam, so hot that steam was all there was, nothing else. If you watch as steam cools, you’ll eventually see some droplets of water begin to form. And if you wait long enough, sooner or later some ice crystals emerge as well. It is, of course, all the same stuff (H2O), simply boiled into a featureless form. In a similar way, the featureless newborn universe was all the same stuff — in this case, stuff that would become all the species of the standard model of particle physics. Quarks (various flavors and colors), leptons (electrons, neutrinos and their cousins), gluons (for holding quarks together), various bosons (for transporting forces back and forth), everything that makes up everything in the world today was waiting to materialize like ice out of the primordial steam. And, like pure radiation, all these entities possessed only energy, no mass.
As the universe expanded and cooled, the particles of matter — a roster using up most of the letters in the Greek alphabet — began to appear. Quarks, for instance, congealed out of the primordial haze, announcing the arrival of the strong nuclear force, no longer indistinguishable from other forces. But still these particles possessed no mass. Like smooth steel balls rolling over perfectly slick ice, nothing resisted their motion. Resistance to motion is inertia. Inertia is the hallmark of mass. No resistance, no inertia, no mass.
In a world without mass, protons and neutrons would form, but electrons would refuse to orbit them. So atoms and molecules could not exist. None of the features of the familiar world would appear.
Less than a nanotick of the cosmic clock later, though, the grandest event in the universe since its birth changed the game. Higgs stuff condensed into a new form. Just as a sufficiently low temperature permits an iron bar’s magnetism, a sufficiently cool universe turned the Higgs field into something that matter had to contend with. Rather than skimming effortlessly over ice, particles now had to swim through a thick ocean, facing resistance to their motion, thereby acquiring mass. And the universe was never to be the same again.
In essence, the Higgs field split the electro­weak force’s personality. Photons, transmitters of electromagnetic influence, were oblivious to the newly palpable Higgs field, and so continued on in their merry massless way, letting there be light. Transmitters of the weak part of the electro­weak force, two W particles (one positively charged, one negative) and the neutral Z particle felt the Higgs force dramatically. While the photon remained massless, for the W’s and the Z, flying though space became more like swimming through molasses. Similarly, quarks felt the Higgs’ presence, also acquiring mass (although not in precisely the same way).
Particles have different masses because they interact with the Higgs field to different degrees. At a nontechnical level, physicists sometimes speak of the field as a flock of paparazzi. Massive particles are like Hollywood celebrities — the paparazzi impede their path. The more famous, the more paparazzi get in the way, so the greater the resistance (or the mass). B actors (lightweights) pass through the paparazzi crowds much more quickly. Massless photons cannot even be linked to Kevin Bacon. They are invisible to the paparazzi.
At least, that’s the story physicists had been telling themselves. It’s so compelling, mathematically and aesthetically, that most experts believed that nature had to follow the script. But doubts nagged many who knew history. An imponderable substance filling all of space, responsible for fundamental physical phenomena? A good description of the ether, the 19th century version of the Higgs field. It turned out that the ether didn’t exist. Some feared the same fate for the Higgs.
But this time came success. Smashing protons at more than 99.999999 percent of the speed of light infused the Higgs field with trillions of electron volts of energy, enough to shake loose the field’s signature particle, the Higgs boson. While its life is short, the daughter particles of the Higgs’ decay register their births in the Large Hadron Collider’s detectors, and the Higgs’ brief presence can be deduced, confirming the reality of its field.
Scottish physicist Peter Higgs conceived of such a field in 1964 and predicted the particle’s existence. He wasn’t the only physicist of that era to devise similar mathematical scenarios. Still others showed how the Higgs idea could orchestrate the breaking of electroweak symmetry. All those participants in elucidating the Higgs’ role in reality shared a common prescience, an ability to see deeply into nature through the lens of mathematics.
Their success illustrates a further meaningfulness of the Higgs discovery: It validates the scientific enterprise as a way of knowing nature. Somehow, humans fiddling with squiggles on paper figured out what you would find if you spent billions of dollars on a machine to create temperatures of a million billion degrees. Scientists figured out one of nature’s deepest secrets just by using their heads.
“This is an enormous triumph for mathematical methods to make predictions for things in the real world,” says physicist Brian Greene. “This Higgs particle has been a hypothetical mathematical symbol in our equations for 40 years.”
During that time most physicists came to believe in the Higgs boson’s existence as an article of scientific faith. Without it, something would be desperately wrong with the entire framework of science’s understanding of the universe. Had the Higgs boson not materialized when the Higgs field was properly probed, it would have been as though Voldemort had succeeded in killing Harry Potter.
Harry triumphed, though, and so has the Higgs. Happily, however, the Higgs discovery is not the last chapter in nature’s final book. There will be sequels. Physicists need more particles, not included in the standard set, to explain mysteries like the abundance of dark matter in space and how gravity fits in with the rest of nature’s forces. And the Higgs boson now discovered may merely be one member of a much larger Higgs family, with cousins performing various other important jobs in constructing the universe.
"At some level we're pretty sure that the standard model is not the full picture," says Incandela. "We're on the frontier now, we're on the edge of a new exploration. Maybe we see nothing extraordinary ... or maybe we open up a whole new realm of discovery."

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