Tag Archives: Higgs boson

BigBang

The Next (and Final) Doomsday Scenario

Personally, I love dystopian visions and apocalyptic nightmares. So, news that the famed Higgs boson may ultimately cause our demise, and incidentally the end of the entire cosmos, caught my attention.

Apparently theoreticians have calculated that the Higgs potential of which the Higgs boson is a manifestation has characteristics that make the universe unstable. (The Higgs was discovered in 2012 by teams at CERN’s Large Hadron Collider.) Luckily for those wishing to avoid the final catastrophe this instability may keep the universe intact for several more billions of years, and if suddenly the Higgs were to trigger the final apocalypse it would be at the speed of light.

From Popular Mechanics:

In July 2012, when scientists at CERN’s Large Hadron Collider culminated decades of work with their discovery of the Higgs boson, most physicists celebrated. Stephen Hawking did not. The famed theorist expressed his disappointmentthat nothing more unusual was found, calling the discovery “a pity in a way.” But did he ever say the Higgs could destroy the universe?

That’s what many reports in the media said earlier this week, quoting a preface Hawking wrote to a book called Starmus. According to The Australian, the preface reads in part: “The Higgs potential has the worrisome feature that it might become metastable at energies above 100 [billion] gigaelectronvolts (GeV). This could mean that the universe could undergo catastrophic vacuum decay, with a bubble of the true vacuum expanding at the speed of light. This could happen at any time and we wouldn’t see it coming.”

What Hawking is talking about here is not the Higgs boson but what’s called the Higgs potential, which are “totally different concepts,” says Katie Mack, a theoretical astrophysicist at Melbourne University. The Higgs field permeates the entire universe, and the Higgs boson is an excitation of that field, just like an electron is an excitation of an electric field. In this analogy, the Higgs potential is like the voltage, determining the value of the field.

Once physicists began to close in on the mass of the Higgs boson, they were able to work out the Higgs potential. That value seemed to reveal that the universe exists in what’s known as a meta-stable vacuum state, or false vacuum, a state that’s stable for now but could slip into the “true” vacuum at any time. This is the catastrophic vacuum decay in Hawking’s warning, though he is not the first to posit the idea.

Is he right?

“There are a couple of really good reasons to think that’s not the end of the story,” Mack says. There are two ways for a meta-stable state to fall off into the true vacuum—one classical way, and one quantum way. The first would occur via a huge energy boost, the 100 billion GeVs Hawking mentions. But, Mack says, the universe already experienced such high energies during the period of inflation just after the big bang. Particles in cosmic rays from space also regularly collide with these kinds of high energies, and yet the vacuum hasn’t collapsed (otherwise, we wouldn’t be here).

“Imagine that somebody hands you a piece of paper and says, ‘This piece of paper has the potential to spontaneously combust,’ and so you might be worried,” Mack says. “But then they tell you 20 years ago it was in a furnace.” If it didn’t combust in the furnace, it’s not likely to combust sitting in your hand.

Of course, there’s always the quantum world to consider, and that’s where things always get weirder. In the quantum world, where the smallest of particles interact, it’s possible for a particle on one side of a barrier to suddenly appear on the other side of the barrier without actually going through it, a phenomenon known as quantum tunneling. If our universe was in fact in a meta-stable state, it could quantum tunnel through the barrier to the vacuum on the other side with no warning, destroying everything in an instant. And while that is theoretically possible, predictions show that if it were to happen, it’s not likely for billions of billions of years. By then, the sun and Earth and you and I and Stephen Hawking will be a distant memory, so it’s probably not worth losing sleep over it.

What’s more likely, Mack says, is that there is some new physics not yet understood that makes our vacuum stable. Physicists know there are parts of the model missing; mysteries like quantum gravity and dark matter that still defy explanation. When two physicists published a paper documenting the Higgs potential conundrum in March, their conclusion was that an explanation lies beyond the Standard Model, not that the universe may collapse at any time.

Read the article here.

BigBang

Time for the Neutrino

Enough of the Higgs boson, already! It’s time to shine the light on its smaller, swifter cousin, the neutrino.

From the NYT:

HAVE you noticed how the Higgs boson has been hogging the limelight lately? For a measly little invisible item, whose significance cannot be explained without appealing to thorny concepts of quantum field theory, it has done pretty well for itself. The struggling starlets of Hollywood could learn a thing or two about the dark art of self-promotion from this boson.

First, its elusiveness “sparked the greatest hunt in science,” as the subtitle of one popular book put it. Then came all the hoopla over its actual discovery. Or should I say discoveries? Because those clever, well-meaning folks at the CERN laboratory outside Geneva proclaimed their finding of the particle not once but twice. First in 2012, on the Fourth of July no less, they told the world that their supergigantic — and awesomely expensive — atom smasher had found tentative evidence of the Higgs. Eight months later, they made a second announcement, this time with more data in hand, to confirm that they had nabbed the beast for real. Just recently, there was yet more fanfare when two of the grandees who had predicted the particle’s existence back in 1964 shared a Nobel Prize for their insight.

In fact, ever since another Nobel-winning genius, Leon Lederman, branded it the “God particle” some 20 years ago, the Higgs boson has captured the public imagination and dominated the media coverage of physics. Some consider Professor Lederman’s moniker a brilliant P.R. move for physics, while others denounce it as a terrible gaffe that confuses people and cheapens a solemn scientific enterprise. Either way, it has been effective. Nobody ever talks about the fascinating lives of other subatomic particles on “Fox and Friends.”

Sure, the story of Higgs is a compelling one. The jaw-dropping $9 billion price tag of the machine built to chase it is enough to command our attention. Plus, there is the serene, wise man at the center of this epic saga: the octogenarian Peter Higgs, finally vindicated after waiting patiently for decades. Professor Higgs was seen to shed a tear of joy at a news conference announcing the discovery, adding tenderness to the triumphant moment and tugging ever so gently at our heartstrings. For reporters looking for a human-interest angle to this complicated scientific brouhaha, that was pure gold.

But I say enough is enough. It is time to give another particle a chance.

And have I got a terrific candidate for you! It moves in mysterious ways, passing right through wood, walls and even our bodies, with nary a bump. It morphs among three forms, like a cosmic chameleon evading capture. It brings us news from the sun’s scorching heart and from the spectacular death throes of monstrous stars. It could tell us why antimatter is so rare in the universe and illuminate the inner workings of our own planet. Someday, it may even help expose rogue nuclear reactors and secret bomb tests, thus promoting world peace. Most important, we might not be here without it.

WHAT is this magical particle, you ask? It is none other than the ghostly neutrino.

O.K., I admit that I am biased, having just written a book about it. But believe me, no other particle comes close to matching the incredibly colorful and quirky personality of the neutrino, or promises to reveal as much about a mind-boggling array of natural phenomena, both subatomic and cosmic. As one researcher told me, “Whenever anything cool happens in the universe, neutrinos are usually involved.” Besides, John Updike considered it worthy of celebrating in a delightful poem in The New Yorker, and on “The Big Bang Theory,” Sheldon Cooper’s idol Professor Proton chose Gino the Neutrino as his beloved puppet sidekick.

Granted, the neutrino does come with some baggage. Remember how it made headlines two years ago for possibly traveling faster than light? Back then, the prospects of time travel and breaking Einstein’s speed limit provided plenty of fodder for rampant speculation and a few bad jokes. In the end, the whole affair turned out to be much ado about a faulty cable. I maintain it is unfair to hold the poor little neutrino responsible for that commotion.

Generally speaking, the neutrino tends to shun the limelight. Actually, it is pathologically shy and hardly ever interacts with other particles. That makes it tough to pin down.

Thankfully, today’s neutrino hunters have a formidable arsenal at their disposal, including newfangled observatories buried deep underground or in the Antarctic ice. Neutrino chasing, once an esoteric sideline, has turned into one of the hottest occupations for the discerning nerd. More eager young ones will surely clamor for entry into the Promised Land now that the magazine Physics World has declared the recent detection of cosmic neutrinos to be the No. 1 physics breakthrough of the year.

Drum roll, please. The neutrino is ready to take center stage. But don’t blink: It zips by at nearly the speed of light.

Read the entire story here.

BigBang

Mr. Higgs

A fascinating profile of Peter Higgs, the theoretical physicist whose name has become associated with the most significant scientific finding of recent times.

From the Guardian:

For scientists of a certain calibre, these early days of October can bring on a bad case of the jitters. The nominations are in. The reports compiled. All that remains is for the Nobel committees to cast their final votes. There are no sure bets on who will win the most prestigious prize in science this year, but there are expectations aplenty. Speak to particle physicists, for example, and one name comes up more than any other. Top of their wishlist of winners – the awards are announced next Tuesday – is the self-deprecating British octagenarian, Peter Higgs.

Higgs, 84, is no household name, but he is closer to being one than any Nobel physics laureate since Richard Feynman, the Manhattan project scientist, who accepted the award reluctantly in 1964. But while Feynman was a showman who adored attention, Higgs is happy when eclipsed by the particle that bears his name, the elusive boson that scientists at Cern’s Large Hadron Collider triumphantly discovered last year.

“He’s modest and actually almost to a fault,” said Alan Walker, a fellow physicist at Edinburgh University, who sat next to Higgs at Cern when scientists revealed they had found the particle.

“You meet many physicists who will tell you how good they are. Peter doesn’t do that.”

Higgs, now professor emeritus at Edinburgh, made his breakthrough the same year Feynman won the Nobel. It was an era when the tools of the trade were pencil and paper. He outlined what came to be known as the Higgs mechanism, an explanation for how elementary particles, which make up all that is around us, gained their masses in the earliest moments after the big bang. Before 1964, the question of why the simplest particles weighed anything at all was met with an embarrassed but honest shrug.

Higgs plays down his role in developing the idea, but there is no dismissing the importance of the theory itself. “He didn’t produce a great deal, but what he did produce is actually quite profound and is one of the keystones of what we now understand as the fundamental building blocks of nature,” Walker said.

Higgs was born in Newcastle in 1929. His father, a BBC sound engineer, brought the family south to Birmingham and then onwards to Bristol. There, Higgs enrolled at what is now Cotham School. He got off to a bad start. One of the first things he did was tumble into a crater left by a second world war bomb in the playground and fracture his left arm. But he was a brilliant student. He won prizes in a haul of subjects – although not, as it happens, in physics.

To the teenage Higgs, physics lacked excitement. The best teachers were off at war, and that no doubt contributed to his attitude. It changed through a chance encounter. While standing around at the back of morning assembly Higgs noticed a name that appeared more than once on the school’s honours board. Higgs wondered who PAM Dirac was and read up on the former pupil. He learned that Paul Dirac was a founding father of quantum theory, and the closest Britain had to an Einstein. Through Dirac, Higgs came to relish the arcane world of theoretical physics.

Higgs found that he was not cut out for experiments, a fact driven home by a series of sometimes dramatic mishaps, but at university he proved himself a formidable theorist. He was the first to sit a six-hour theory exam at Kings College London, and for the want of a better idea, his tutors posed him a question that had recently been solved in a leading physics journal.

“Peter sailed ahead, took it seriously, thought about it, and in that six-hour time scale had managed to solve it, had written it up and presented it,” said Michael Fisher, a friend from Kings.

But getting the right answer was only the start. “In the long run it turned out, when it was actually graded, that Peter had done a better paper than the original they took from the literature.”

Higgs’s great discovery came at Edinburgh University, where he was considered an outsider for plugging away at ideas that many physicists had abandoned. But his doggedness paid off.

At the time an argument was raging in the field over a way that particles might gain their masses. The theory in question was clearly wrong, but Higgs saw why and how to fix it. He published a short note in September 1964 and swiftly wrote a more expansive follow-up paper.

To his dismay the article was rejected, ironically by an editor at Cern. Indignant at the decision, Higgs added two paragraphs to the paper and published it in a rival US journal instead. In the penultimate sentence was the first mention of what became known as the Higgs boson.

At first, there was plenty of resistance to Higgs’s theory. Before giving a talk at Harvard in 1966, a senior physicist, the late Sidney Coleman, told his class some idiot was coming to see them. “And you’re going to tear him to shreds.” Higgs stuck to his guns. Eventually he won them over.

Ken Peach, an Oxford physics professor who worked with Higgs in Edinburgh, said the determination was classic Peter: “There is an inner toughness, some steely resolve, which is not quite immediately apparent,” he said.

It was on display again when Stephen Hawking suggested the Higgs boson would never be found. Higgs hit back, saying that Hawking’s celebrity status meant he got away with pronouncements that others would not.

Higgs was at one time deeply involved in the Campaign for Nuclear Disarmament, but left when the organisation extended its protests to nuclear power. He felt CND had confused controlled and uncontrolled release of nuclear energy. He also joined Greenpeace but quit that organisation, too, when he felt its ideologies had started to trump its science.

“The one thing you get from Peter is that he is his own person,” said Walker.

Higgs was not the only scientist to come up with the theory of particle masses in 1964. François Englert and Robert Brout at the Free University in Brussels beat him into print by two weeks, but failed to mention the crucial new particle that scientists would need to prove the theory right. Three others, Gerry Guralnik, , Dick Hagen and Tom Kibble, had worked out the theory too, and published a month later.

Higgs is not comfortable taking all the credit for the work, and goes to great pains to list all the others whose work he built on. But in the community he is revered. When Higgs walked into the Cern auditorium last year to hear scientists tell the world about the discovery, he was welcomed with a standing ovation. He nodded off during the talks, but was awake at the end, when the crowd erupted as the significance of the achievement became clear. At that moment, he was caught on camera reaching for a handkerchief and dabbing his eyes. “He was tearful,” said Walker. “He was really deeply moved. I think he was absolutely surprised by the atmosphere of the room.”

Read the entire article here.

Image: Ken Currie, Portrait of Peter Higgs, 2008. Courtesy of Wikipedia.

BigBang

Fields from Dreams

It’s time to abandon the notion that you, and everything around you, is made up of tiny particles and their subatomic constituents. You are nothing more than perturbations in the field, or fields. Nothing more. Theoretical physicist Sean Carroll explains all.

From Symmetry:

When scientists talk to non-scientists about particle physics, they talk about the smallest building blocks of matter: what you get when you divide cells and molecules into tinier and tinier bits until you can’t divide them any more.

That’s one way of looking at things. But it’s not really the way things are, said Caltech theoretical physicist Sean Carroll in a lecture at Fermilab. And if physicists really want other people to appreciate the discovery of the Higgs boson, he said, it’s time to tell them the rest of the story.

“To understand what is going on, you actually need to give up a little bit on the notion of particles,” Carroll said in the June lecture.

Instead, think in terms of fields.

You’re already familiar with some fields. When you hold two magnets close together, you can feel their attraction or repulsion before they even touch—an interaction between two magnetic fields. Likewise, you know that when you jump in the air, you’re going to come back down. That’s because you live in Earth’s gravitational field.

Carroll’s stunner, at least to many non-scientists, is this: Every particle is actually a field. The universe is full of fields, and what we think of as particles are just excitations of those fields, like waves in an ocean. An electron, for example, is just an excitation of an electron field.

This may seem counterintuitive, but seeing the world in terms of fields actually helps make sense of some otherwise confusing facts of particle physics.

When a radioactive material decays, for example, we think of it as spitting out different kinds of particles. Neutrons decay into protons, electrons and neutrinos. Those protons, electrons and neutrinos aren’t hiding inside neutrons, waiting to get out. Yet they appear when neutrons decay.

If we think in terms of fields, this sudden appearance of new kinds of particles starts to make more sense. The energy and excitation of one field transfers to others as they vibrate against each other, making it seem like new types of particles are appearing.

Thinking in fields provides a clearer picture of how scientists are able to make massive particles like Higgs bosons in the Large Hadron Collider. The LHC smashes bunches of energetic protons into one another, and scientists study those collisions.

“There’s an analogy that’s often used here,” Carroll said, “that doing particle physics is like smashing two watches together and trying to figure out how watches work by watching all the pieces fall apart.

“This analogy is terrible for many reasons,” he said. “The primary one is that what’s coming out when you smash particles together is not what was inside the original particles. … [Instead,] it’s like you smash two Timex watches together and a Rolex pops out.”

What’s really happening in LHC collisions is that especially excited excitations of a field—the energetic protons—are vibrating together and transfering their energy to adjacent fields, forming new excitations that we see as new particles—such as Higgs bosons.

Thinking in fields can also better explain how the Higgs works. Higgs bosons themselves do not give other particles mass by, say, sticking to them in clumps. Instead, the Higgs field interacts with other fields, giving them—and, by extension, their particles—mass.

Read the entire article here.

Image: iron filing magnetic field lines between two bar magnets. Courtesy of Wikimedia.

BigBang

Higgs?

 

A week ago, on July 4, 2012 researchers at CERN told the world that they had found evidence of a new fundamental particle — the so-called Higgs boson, or something closely similar. If further particle collisions at CERN’s Large Hadron Collider uphold this finding over the coming years, this will rank as significant a discovery as that of the proton or the electro-magnetic force. While practical application of this discovery, in our lifetimes at least, is likely to be scant, it undeniably furthers our quest to understand the underlying mechanism of our existence.

So where might this discovery lead next?

[div class=attrib]From the New Scientist:[end-div]

“As a layman, I would say, I think we have it,” said Rolf-Dieter Heuer, director general of CERN at Wednesday’s seminar announcing the results of the search for the Higgs boson. But when pressed by journalists afterwards on what exactly “it” was, things got more complicated. “We have discovered a boson – now we have to find out what boson it is,” he said cryptically. Eh? What kind of particle could it be if it isn’t the Higgs boson? And why would it show up right where scientists were looking for the Higgs? We asked scientists at CERN to explain.

If we don’t know the new particle is a Higgs, what do we know about it?
We know it is some kind of boson, says Vivek Sharma of CMS, one of the two Large Hadron Collider experiments that presented results on Wednesday. There are only two types of elementary particle in the standard model: fermions, which include electrons, quarks and neutrinos, and bosons, which include photons and the W and Z bosons. The Higgs is a boson – and we know the new particle is too because one of the things it decays into is a pair of high-energy photons, or gamma rays. According to the rules of mathematical symmetry, only a boson could decay into exactly two other photons.

Anything else?
Another thing we can say about the new particle is that nothing yet suggests it isn’t a Higgs. The standard model, our leading explanation for the known particles and the forces that act on them, predicts the rate at which a Higgs of a given mass should decay into various particles. The rates of decay reported for the new particle yesterday are not exactly what would be predicted for its mass of about 125 gigaelectronvolts (GeV) – leaving the door open to more exotic stuff. “If there is such a thing as a 125 GeV Higgs, we know what its rate of decay should be,” says Sharma. But the decay rates are close enough for the differences to be statistical anomalies that will disappear once more data is taken. “There are no serious inconsistencies,” says Joe Incandela, head of CMS, who reported the results on Wednesday.

In that case, are the CERN scientists just being too cautious? What would be enough evidence to call it a Higgs boson?
As there could be many different kinds of Higgs bosons, there’s no straight answer. An easier question to answer is: what would make the new particle neatly fulfil the Higgs boson’s duty in the standard model? Number one is to give other particles mass via the Higgs field – an omnipresent entity that “slows” some particles down more than others, resulting in mass. Any particle that makes up this field must be “scalar”. The opposite of a vector, this means that, unlike a magnetic field, or gravity, it doesn’t have any directionality. “Only a scalar boson fixes the problem,” says Oliver Buchmueller, also of CMS.

When will we know whether it’s a scalar boson?
By the end of the year, reckons Buchmueller, when at least one outstanding property of the new particle – its spin – should be determined. Scalars’ lack of directionality means they have spin 0. As the particle is a boson, we already know its spin is a whole number and as it decays into two photons, mathematical symmetry again dictates that the spin can’t be 1. Buchmueller says LHC researchers will able to determine whether it has a spin of 0 or 2 by examining whether the Higgs’ decay particles shoot into the detector in all directions or with a preferred direction – the former would suggest spin 0. “Most people think it is a scalar, but it still needs to be proven,” says Buchmueller. Sharma is pretty sure it’s a scalar boson – that’s because it is more difficult to make a boson with spin 2. He adds that, although it is expected, confirmation that this is a scalar boson is still very exciting: “The beautiful thing is, if this turns out to be a scalar particle, we are seeing a new kind of particle. We have never seen a fundamental particle that is a scalar.”

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image: A typical candidate event including two high-energy photons whose energy (depicted by dashed yellow lines and red towers) is measured in the CMS electromagnetic calorimeter. The yellow lines are the measured tracks of other particles produced in the collision.[end-div]