The apparent discovery of the Higgs boson was hailed as a historic milestone, but for particle physicists it mainly marks the beginning of a new search. Rival teams at CERN in Switzerland are trying to decipher the secrets of antimatter. This photo shows the Large Hadron Collider at CERN.
The British physicist Paul Dirac is seen as the father of antimatter.
The Alpha Magnetic Spectrometer on the International Space Station is looking for traces of antimatter in space.
Nobel laureate Samuel Ting is the head of the Alpha Magnetic Spectrometer project (1976 photo).
John Ellis (right, seen here with Stephen Hawking) is one of CERN’s top theoretical physicists.
Traces of proton-proton collisions measured by the European Organization for Nuclear Research in the search for Higgs boson
CERN Director on Finding Higgs ‘The Real Work Has only Just Begun’
In a SPIEGEL interview, physicist Rolf-Dieter Heuer, general director of the particle physics research center at CERN near Geneva, discusses the remaining unsolved mysteries in his field following the spectacular discovery of the Higgs boson.
SPIEGEL:Mr. Heuer, now that the Higgs boson has finally been discovered at CERN, are there plans to shut down the particle accelerator?
Heuer:By no means. We have achieved a breakthrough, but the real work has only just begun. We need to measure our find, observe its interaction with other particles and also determine its properties. And if, when doing that, we find something that contradicts our theory, then that will automatically open the door to a new type of physics. After all, our so-called Standard Model only describes 4 to 5 percent of our universe.
SPIEGEL: And the rest?
Heuer: About one-fourth is made up of dark matter. It’s what keeps the rotating galaxies from simply flying apart. That cannot be explained with visible matter alone. What we call dark energy accounts for the almost three-fourths that remain. It causes the universe to expand at an ever faster rate. But we still don’t understand the mechanism which expands space equally in all directions.
SPIEGEL: Could the Higgs provide new clues?
Heuer: The Higgs field, which is part of the particle, has a decisive characteristic that fits with dark energy: It works in all directions simultaneously.
SPIEGEL: So Higgs could be the bridgehead to the unknown?
Heuer: Precisely. We don’t know if it has anything to do with dark energy. But we suspect that there is a similar field beyond the Standard Model — the other end of the bridgehead, so to speak.
SPIEGEL: And what if Higgs doesn’t do you the favor of revealing such secrets?
Heuer: We will still have found a particle that helps provide all other particles with mass. It finally proves that our Standard Model is completely accurate. What we must do now is find the hole in this model through which we can advance to the remaining 95 percent of the universe. We still don’t know what role the particle we have found plays. It’s like catching sight of your best friend from a distance. At first it could also be someone who looks a lot like that person, but it turns out to be someone totally different. You only find out for sure when you get closer.
SPIEGEL: What do you plan to do next?
Heuer: By the end of the year, we plan to fire protons at each other. Then we will shut down the accelerator for around two years for maintenance work. When it goes back into commission, things will get exciting: Step by step we will double the energy, allowing us to create particles with ever greater mass. And it could be that by doing so, we will also exceed the threshold to dark matter. That would open new doors.
SPIEGEL: What do you hope to find?
Heuer: Primarily the first traces of supersymmetry. That’s the name of the theory which holds that every particle also has a shadow particle — a mirror world predicted by the theory of anti-matter. Supersymmetry’s lightest particle could be stable enough to be within the reach of our accelerator. That would be a good candidate for dark matter. If we find it, it would represent a massive leap forward.
SPIEGEL: Do you know exactly where you need to search? Or do you just look randomly?
Heuer: Both. We have to be entirely open to unexpected findings. Still, with supersymmetry, we already have a direction and our search is targeted. But it will no longer be as focused as it was with Higgs.
SPIEGEL: When searching for Higgs, you essentially had a ready-made profile of the particle, the one published by Peter Higgs in 1964. Does he deserve the Nobel prize?
Heuer: I think so. But there are also others who were working on similar models back then …
SPIEGEL: … while the Nobel rules only allow for a maximum of three prize winners at a time.
Heuer: Yes, that needs to be changed. In many areas of research — from particle physics to genetics — ever larger groups of people work together because that’s the only way it can work. At some point, the time will have passed when individuals are capable of major discoveries.
SPIEGEL: How many researchers were involved in the long journey towards finding Higgs?
Heuer: In the end, between three and four thousand took part in each of the two major participating experiments.
SPIEGEL: Are such large groups able to change focus and commit to new goals? Or will each researcher soon go back to doing his or her own thing?
Heuer: No, our people will surely stick with it, especially now. The ability to work together has to be in the blood of particle physicists. They learn very early on that it is impossible to advance on one’s own and that constant exchange is necessary.
SPIEGEL: Doesn’t an individual’s achievements get lost in the crowd?
Heuer: No, it is still very easy to identify an excellent physicist. Good people climb quickly — just like in a company.
SPIEGEL: How large can research teams be and still remain manageable?
Heuer: Fifteen years ago, I led a project with 350 people. At the time we thought that was the upper end. Now we have 10 times as many. I would say the real limits we are experiencing are in technology and in the detectors that we are capable of building.
SPIEGEL: For how much longer will you be able to continue conducting experiments with the Large Hadron Collider? At which point will it have done its duty?
Heuer:We are planning up until 2030. It may be worthwhile to upgrade the machine again during the 2020s — for a relatively low extra investment, we would then be able to collide considerably more particles. But it depends on what we have found by that time.
SPIEGEL: And afterwards? Will you need even bigger machines?
Heuer: It’s the energy, and not the size, that is decisive. The closer we want to look, the faster we have to accelerate the particles. In our case, it’s the protons. A lot suggests that our next undertaking will be an accelerator that fires electrons at positrons. That would open up a new view of matter, and of the Higgs particle. There are already plans for it. The main question is which region of the world would be ready to build such a machine?
Interview conducted by Manfred Dworschak
Finding the Anti-World The Next Holy Grail for Physics
The apparent discovery of the Higgs boson was hailed as a historic milestone, but for particle physicists it mainly marks the beginning of a new search. Rival teams at CERN in Switzerland are trying to decipher the secrets of antimatter. If they succeed, the laws of physics will have to be rewritten.
Sheep are grazing to the left of the gate to the anti-world. On the right-hand side, a pair of rust-brown steel bottles is waiting to be picked up. A sign warns: “Caution. Radiation!” Another sign prohibits the use of bicycles.
A yellow steel door leads into the interior of the so-called AD building on the grounds of the CERN research center near Geneva, Switzerland. The machine that was built here is called the anti-proton decelerator. The rhythmic hissing and thumping sounds of vacuum pumps and cryo-aggregates combine with the dull droning of the air-conditioning system. This is where scientists are making a material that is highly mysterious because it probably doesn’t exist anywhere else in the universe: anti-atoms.
About 4 meters (13 feet) off the ground, a catwalk leads through a bizarre landscape of cables, tubes and concrete. This vantage point offers a glimpse into laboratory rooms in which scientists climb around among magnets, electronic equipment, helium tanks and beamlines. Their goal is to explore the realm of antimatter.
Separated from each other by small gates, four teams are competing to unlock the secrets of nature. Their facility is a factory of sorts for so-called anti-particles. Here, the scientists guide, cool, slow down and centrifuge the artificially generated particles. In the process, they learn which forms of manipulation are possible with this material from a mysterious alternative world. One of them calls it “particle gymnastics.”
‘The Race Is On’
The words “The race is on” are written on the container where the measurements are done. Jeffrey Hangst, the director of the project, is proud of the fact that his team is ahead in the race. Hangst spent 15 years developing his equipment, and now he is reaping the benefits.
Hangst is the world’s first scientist to successfully capture individual anti-hydrogen atoms in magnetic traps. No one else has managed to keep the atoms captive for an entire quarter of an hour. And then, in what was a sensation for physicists, he performed the first successful measurement of one of these antiatoms.
The accelerator ring where Hangst does his experiments was once the centerpiece of CERN, earning the center international fame and its developers, Simon van der Meer and Carlo Rubbia, the Nobel Prize. Today, however, the anti-proton decelerator is hidden in a dead-end street. The antimatter factory isn’t easy to find among the office buildings, workshops and machine buildings at CERN.
Public attention has long since turned to the new, enormous super-accelerator called the Large Hadron Collider (LHC) — especially in recent days.
Last week, physicists at CERN proudly announced that the LHC had achieved its first important partial victory: The data that were presented at the major summer conference of particle physicists in Melbourne leave almost no doubt anymore that the so-called Higgs boson, which gives other particles their mass, has finally been found. The discovery marks the end of a hunt that has lasted almost 50 years.
‘The Work Has Just Begun’
“It’s hard not to get excited by these results,” says Sergio Bertolucci, the research director at CERN. He and his colleagues agree that this is a great moment in the history of their field — perhaps the discovery of the century. And yet it was also a discovery that they had all expected. It would have been more surprising if they had not found the Higgs particle, because it would have destroyed the current standard theory of particle physics.
Seen in this light, the scientists are not as excited about what they have finally achieved as they are about what lies ahead. “The real work has just begun,” says CERN Director General Rolf-Dieter Heuer.
That’s because the discovery of the Higgs boson merely serves as yet another confirmation of an existing theory. Physicists agree that they are now entering terrain in which they will no longer be guided by the existing equations. What happens next is uncertain.
The known formulas are not sufficient to help us understand why the world is this way and not that, and to comprehend in detail how the universe was created during the Big Bang. To delve into those secrets, it will be necessary to decipher new laws of nature.
Whatever Happened to Antimatter?
One of the central puzzles that could pave the way into this new territory lies in the question that Jeffrey Hangst has chosen to pursue: Why does the world consist of matter? And what happened to antimatter?
Hangst is particularly interested in an unusual material. It behaves just like ordinary matter, and yet it’s completely different. The properties are the same, meaning that anti-glass would splinter like glass, anti-gold would shine like gold and anti-water would splash like water. And there would also be no visible difference between a person made of normal matter and a person made of antimatter. They would be completely identical.
But heaven forbid that both — matter and antimatter, image and copy — come into contact with one another. If that happened, there would be a bright flash of light and suddenly both would have disappeared.
The most important thing, however, is the fact that antimatter doesn’t actually exist on a sustained basis. The anti-world is nothing more than a possibility, one that nature has apparently not made into a reality. In the theorists’ equations both the world and the anti-world play equal roles. But in the real, observable universe, everything consists of matter, not antimatter.
“Understanding why this is the case has always fascinated me,” says Hangst. Physicists are convinced that properly understanding the relationship between matter and antimatter would be tantamount to a revolution in comprehending the universe.
Something Instead of Nothing
Back in the mid-19th century, German philosopher Friedrich Wilhelm Schelling came up with what he called the “final, desperation-filled question”: Why is there anything at all? Why is there not nothing? In modern physics, Schelling’s metaphysical astonishment has been rephrased: Why don’t matter and antimatter exist in equal parts in the universe?
Physicists agree that the force of the Big Bang created both forms of existence in equal amounts. With each particle, its counterpart, the corresponding antiparticle, was born. And because nature gave both the capacity to destroy one another, the moment of their creation already included the seeds of their demise.
But then some providential change must have fundamentally altered the course of the universe. Physicists would love to understand what exactly happened shortly after the Big Bang. At this point, they only know the results of those events early in the history of the cosmos: They led to matter gaining the upper hand over antimatter.
But by no means was it by a large margin. On the contrary, the ratio that once existed between the two types of particles can be calculated using the density of particles in today’s universe. The result is astonishing: There were 1,000,000,001 particles to 1,000,000,000 antiparticles. Can such a miniscule imbalance be significant?
Yes, it can. The subsequent evolution of the universe would reveal that this one particle was critical. If matter and antimatter had been exactly equal, cosmic existence would have destroyed itself within fractions of a second, leaving nothing behind but a monotonous desert of radiation.
No galaxies, no stars and no planets, and not even the most ordinary of atoms would have been created in the universe without this small imbalance — and humanity would certainly not have had the opportunity to ponder the mysteries of existence. The universe would have been nothing but a massive, constantly expanding ball of light.
Thanks to this tiny imbalance, however, there were survivors of the cosmic conflagration. In a furious inferno, matter and antimatter were incinerated, yielding pure radiation energy, which still exists today in the form of the background radiation that fills the entire universe. But the small remnant, that tiny excess of matter, survived and formed the seed of everything we marvel at today in the starlit sky. And everything that forms mountains, oceans, plants, animals and human beings on the Earth also stems from the remnants of that huge orgy of destruction that marked the beginning of cosmic history.
Ever since physicists recognized that all the diversity and complexity in this world is attributable to the victory of matter over antimatter, one of the great challenges of their field has been to solve the question of what caused that mysterious imbalance in the first place. Although physicists have been able to reconstruct the processes of the Big Bang in astounding detail, this fundamental question still remains unanswered.
But now the big search for answers has begun, a search that involves the use of technology on a massive scale:
- At the Brookhaven National Laboratory outside New York City, scientists are smashing together gold ions at nearly the speed of light. Last year, they managed to identify 18 anti-helium nuclei, the largest antiparticles detected to date, in the inferno of many billions of particle fragments.
- In a bid to detect even larger particles of antimatter, particle physicists have set up experimental apparatus in space. Their detector, which is docked to the International Space Station (ISS), has been listening for signals from the anti-world since May of last year.
- In Japan, scientists are bombarding a tank filled with 50,000 tons of highly purified water with neutrinos. Their goal is to detect tiny differences in the properties of neutrinos and their antiparticles, anti-neutrinos.
- One of the four massive underground detectors at the LHC at CERN is devoted primarily to one task: detecting differences in the behavior of matter and antimatter.
Part 2: How ‘the Strangest Man’ Revolutionized Physics
But the first insight into the realm of antiparticles was gained at a desk, and not in the laboratory. Paul Dirac (1902 to 1984), the discoverer of the anti-world, was a gaunt, pale Englishman who was noticeable for his awkward behavior and his almost pathological reticence. Even in the community of quantum physics pioneers, which was not exactly short of eccentrics, Dirac was seen as exotic. The Danish physicist Niels Bohr described him as “the strangest man,” while Albert Einstein was concerned about Dirac’s balancing act between genius and madness.
Social settings made Dirac uncomfortable, and he even avoided working with others in his field, theoretical physics. In conversation, there were only three subjects which would prompt him to string together a few coherent sentences: Mickey Mouse, Chopin’s waltzes and the singer Cher.
Dirac was happiest when he could be alone with his equations. His colleagues both admired and feared the brilliance of this eccentric Englishman.
According to a story related by the German physicist Werner Heisenberg, he and Dirac were once traveling on a ship to Japan together when Dirac asked him why he liked to dance. When Heisenberg explained that it was a pleasure to dance with nice girls, Dirac replied: “Heisenberg, how do you know beforehand that the girls are nice?”
Dirac was completely baffled by Robert Oppenheimer’s interest in poetry. “In science,” he is quoted as saying, “you want to say something that nobody knew before, in words which everyone can understand. In poetry you are bound to say … something that everyone knows already in words that nobody can understand.”
The Beauty of Equations
While Dirac seemed to lack the capacity for interpersonal relations, he was all the more obsessed with the elegance of formulas. Probably like no other physicist, he was guided by a desire for mathematical harmony. He was deeply convinced that the truth could be found in the beauty of equations.
It was no accident that Dirac, the magician of formulas, devised the equation that was named after him, an equation that his colleagues perceived as an “absolute miracle.”
Dirac had long been searching for a new, improved theory of electrons when, at the end of 1927, he finally stumbled upon a formula of beguiling simplicity. Suddenly it seemed possible to explain the properties of the electron in a completely new way. Frank Wilczek, who, like Max Born, was later honored with the Nobel Prize, described Dirac’s equation as “painfully beautiful.” At only 25, Dirac had secured his place as a superstar in the relatively new field of quantum physics.
But there was a small problem. Dirac’s theory described the electron precisely, but it also predicted the existence of a second, mysterious twin particle, albeit with opposite polarity. What were scientists to make of this strange quirk of mathematics?
At first, scientists tried in vain to make the troublesome ghost particle disappear with mathematical tricks. But it stubbornly resisted all of their efforts.
Messengers from the Universe
The term “anti-electron” first appeared in an article by Dirac in 1931. But not even Dirac himself seemed to have complete confidence in his theory. He left it unclear as to whether he was referring to a truly detectable particle. To Dirac, it must have seemed too preposterous to postulate the existence of an entire anti-world solely on the basis of a formula. Dirac was later asked why he hadn’t clearly predicted the new particle at the time. “Pure cowardice,” he replied.
Even when Carl Anderson, a 26-year-old American, made his great discovery, it went almost unnoticed in the scientific community at first. In the air-and-alcohol mixture of a cloud chamber, Anderson had seen strange strips of condensation that looked as if they came from positively charged electrons. But no one drew the conclusion that these could have been the anti-electrons Dirac had described.
The breakthrough came in a lecture at the Royal Society in London, where the results from the United States were presented. The audience was mesmerized by photos of the ghostlike particle trails. It seemed as if messengers from the depths of the universe were raining down on planet Earth. Upon impact, they created particle-antiparticle pairs that disappeared into nothingness shortly thereafter.
The most elementary form of creation and destruction was unfolding before the eyes of the audience. The speaker, Patrick Blackett, called it the “death pact.”
Fuelling the Imagination
A new element entered the world of science fiction on that day. The term “anti-world” alone is enough to inspire fantasies, suggesting the possibility of another, opposite form of existence. Heaven and hell, Christ and Antichrist, matter and antimatter — could there be a connection?
But antimatter is also fascinating beyond all metaphysical speculation, especially as it reveals the full explosive force of Einstein’s famous formula, E = mc2. Mass, as the equation states, is nothing but highly concentrated energy. Normally, however, that energy is “trapped” in the form of matter. But when a particle and its antiparticle collide, this energy is released immediately — and in an impressive quantity. About a teaspoon of matter, combined with the corresponding amount of antimatter, is enough to unleash the destructive power of the Hiroshima bomb.
Not surprisingly, antimatter usually plays either the role of a super-fuel or a super-bomb in the utopias of science fiction authors. Either power-hungry extraterrestrials are destroying planets with their antimatter cannons, or megacities are slurping all of their energy from small tubes of antimatter. In his novel “Angels & Demons,” the author Dan Brown describes a hunt for a canister of antimatter with which the secret society of the Illuminati plans to destroy the Vatican. And the fictional starship USS Enterprise of “Star Trek” fame can only embark on its expeditions to distant civilizations because antimatter is fueling its warp drive.
Physicists, however, have never nourished any great hopes of being able to make such visions reality. That’s because they know that all the world’s antiproton factories combined produce less than a billionth of a gram of antimatter per year. At this rate, they would have had to start production well before the Big Bang to make a single super-bomb — not to mention the problem of having to store the antimatter for such a long time without triggering a premature explosion.
Meanwhile, physicists have found other practical applications for the antimatter produced in the laboratory. Positron emission tomography (PET), for example, made it possible to look into the thinking brain for the first time. Using hamster cells, scientists at CERN are currently testing the efficacy of antiproton radiation in destroying tumors. Positronium containing antimatter, on the other hand, could be used to detect tiny hairline cracks in turbines.
The Very Small and the Very Large
But the real fascination with antimatter is not a technical but of a philosophical nature. It played a key role in modern physics’ spectacular attempt to bridge the gap between the microcosm and the macrocosm.
In the 1960s, scientists became aware of how closely particle physics and cosmology — the sciences of the very small and the very large — are interconnected. The deeper physicists penetrated into the subatomic world, the more they learned about the early days of the cosmos. It was there, in the delivery room of the universe, that the symmetry between matter and antimatter, which makes all material existence possible, must have come about.
The decisive connection was established by a physicist who ultimately won the Nobel Prize, albeit not for his research into physics but for his contribution to world peace. At about the same time at which he was gradually becoming a dissident, Andrei Sakharov, one of the fathers of the Soviet hydrogen bomb, also became interested in questions of cosmology.
Cut off from his Western colleagues, he mulled over the question of how matter could have achieved its victory over antimatter — and formulated conditions under which this could have been possible.
It must have happened in the middle of the birth pangs of the universe, only fractions of a second after the beginning of time. Just as ice changes all of its properties when it turns into water, the entire, seething and bubbling universe must have undergone a transformation — a “hiccup,” as CERN theoretician John Ellis puts it. And there was something else, too. Sakharov theorized that somewhere deep within its laws, nature treats the seemingly identical twins of matter and antimatter differently.
What Sakharov had postulated seemed bold and speculative, and yet nature seemed to want to prove him right. A sensational discovery had just shaken the world of particle physics. So-called kaons, extremely short-lived and otherwise not particularly remarkable residents of the particle zoo, apparently decayed in a different manner than their counterparts, the anti-kaons.
The difference is admittedly tiny — far too small, in fact, to satisfactorily explain the quantity of matter in the universe. Nevertheless, a dam had been breached, now that someone had proven that antimatter is not the exact counterpart of matter. There are differences. Particle physicists, seeking to gain a better understanding of what those differences are, embarked on a global hunt for other asymmetries. The most determined among them are the scientists at CERN.
‘The First Truly Exciting Result’
There, beneath the peaks of the Jura Mountains, about 10,000 scientists have made it their mission to make protons crash into each other with the greatest possible force. Bundles of particles, accelerated by giant magnets, speed around a 27-kilometer circular tunnel. They rush from Switzerland to France and back again, 11,200 times per second, until they eventually crash and explode.
Then the scientists study the resulting mist of particle fragments. Their goal is to find new physics, or phenomena that cannot be explained with the known body of formulas in particle physics. They know that the answers to the great puzzles of particle physics must be hidden somewhere out there, in forms of energy never explored before — as well as the secret that makes antimatter comprehensible in the first place.
CERN’s ground-breaking apparatus went into operation two-and-a-half years ago. For two years — to widespread disappointment — it seemed as if nature were adhering strictly to the known formulas.
Then, at the end of last year, the first indication of a new physics appeared to finally have been revealed. The news, at the time, did not come from the Higgs boson hunters at the two giant detectors, Atlas and CMS, who were being celebrated last week. Instead, a smaller team at the LHCb experiment announced the discovery. (The world of CERN is so unusual that a team of 750 scientists from 15 countries can be considered small.)
“It’s the first truly exciting result the accelerator has delivered,” says LHCb physicist Thomas Ruf, his voice filled with pride. He flips through the “Particle Data Booklet,” a small brochure that lists all the kaons, muons, omega, lambda and sigma particles in the particle world — a standard feature on the desk of every particle physicist.
Stronger than Expected
The booklet lists dozens of possible decay processes for which asymmetries between matter and antimatter have since been discovered. But it’s different this time, because the effect is five or even 10 times as stronger as it ought to be. Most importantly, it is occurring in so-called D mesons, particles that contain only one charm quark. Few scientists had even considered this possibility until now.
And now the theoreticians are eagerly embarking on the study of the behavior of charm quarks, which had previously always been neglected. The LHCb physicists are trying to recalibrate their device to make it as sensitive as possible to the decay of D mesons.
Ruf and his colleagues hope to find other surprises in the data from the LHCb collaboration. And then there are the remaining results from last year, which haven’t been fully analyzed yet, and that more than a dozen scientists are currently studying. Will the data confirm the D meson effect? They don’t know yet, because all of the data they receive is distorted — deliberately.
To prevent the scientists from being blinded by their own euphoria while analyzing the data, the results are essentially obfuscated with the help of special software. Only when the analysis is complete and has been determined to be sound will the data be “unblinded,” to use the scientists’ terminology.” Then it will become apparent whether there is evidence to substantiate the scientists’ ideas.
Part 3: Searching for Antimatter in Space
Another scientist who has set up camp at CERN is also hoping for answers: Nobel laureate Samuel Ting. But it isn’t in the accelerator tunnel deep beneath the earth, but 400 kilometers above it, that Ting believes he can find the answer to the antimatter mystery.
From a distance, an eye-catching sign draws attention to the building where he works. It depicts radiation raining down on planet Earth as if it were faraway stardust.
This is Ting’s laboratory. He was the one who, in the face of great resistance, saw to it that the ISS was equipped with a particle detector last year. Even when the space shuttle Columbia, which was intended to carry his equipment to the ISS, exploded, he didn’t abandon his mission. Ting kept up his lobbying efforts in Washington until an additional shuttle flight was approved for his experiment. Apparently politicians are also fascinated by the goal of searching for antimatter in space.
It was truly a bold proposition, and one that was met with great skepticism among Ting’s colleagues: $1.5 billion for an experiment that very few believed stood a chance of succeeding. Some felt that it was a ludicrous project.
Looking in Unusual Places
But Ting was unstoppable. “It’s always the same with truly unusual ideas. The theoreticians say: ‘This won’t achieve anything,’ and the experimenters say: ‘This won’t work,'” he says.
When he came from Taiwan to the United States, says Ting, he had no more than $100 in his pocket, and yet he managed to have a successful career. As a particle physicist, he later searched in places where no one expected surprises — and it got him a Nobel Prize in the end. Why should he be wrong this time?
“They’ve been looking for antimatter for decades,” Ting scoffs. “And what have they found so far? Nothing.”
That’s why it’s time to ask a completely different question, says Ting: What if antimatter didn’t disappear at all? What if it merely exists in other regions of the universe?
In fact, antimatter discoverer Dirac also speculated that perhaps it’s only a coincidence that the Earth consists of matter. “It is quite possible that for some of the stars it is the other way about,” he said in his Nobel lecture.
This cannot be detected with telescopes alone, Ting explains, which is precisely why he had the 8.5-ton Alpha Magnetic Spectrometer (AMS) transported into space. If any anti-atoms ever strayed into our corner of the Milky Way, the AMS could track them down. And only a single atom of anti-silicon or anti-carbon would be enough to convince the scientific world that anti-stars and entire anti-galaxies must exist somewhere in the universe.
Keeping It Short and Sweet
Ting is not short on self-confidence. The AMS is unique among particle physics experiments in that it is entirely tailored to the wishes of the project’s leader. In other projects, it is the collective of scientists that counts. Here, the focus is entirely on Ting.
Every day, just before 5 p.m., the members of his team emerge from the surrounding buildings and briefly assemble in the lobby, where some play with the solar paddles of the ISS model while others watch as the cloud-covered Atlantic slowly passes across a giant monitor. The images are live footage from space, transmitted by a kind of webcam on the space station.
Then, at 5 p.m. on the dot, everyone goes into Ting’s office. He sits enthroned at a massive oak desk with room for at least two dozen scientists. The front of the office, which Ting faces, is made of glass, enabling him to look down into the control room, where technicians monitor their extraterrestrial laboratory around the clock, 365 days a year. But now Ting presses a button and a screen comes down from the ceiling, blocking the view of the control room.
The status report appears on the screen, showing events from the last 24 hours. Temperature? Signals? Irregularities? Speaking quietly but assertively, Ting asks his questions. The answers are prompt and brief.
There have been no unusual events, and at 5:04 the scientists return to their work. “In Mao’s ‘Little Red Book,’ it says that the most important thing about conferences is that they should be short,” says Ting.
In their laboratory in space, the cosmic particle hunters have already caught material from far away more than 17 billion times. They have been able to detect almost all elements in the periodic table, including helium, silicon, carbon, iron and others. But Ting doesn’t want to reveal whether there are also indications of anti-helium or even more complex particles of antimatter in the cosmic radiation. “I can only promise one thing,” he says. “I will publish as late as possible. I want to be completely sure of myself first.”
Jeffrey Hangst and the other scientists in the AD building are approaching the antimatter problem in a relatively direct way. Plasma, high energy, laser and nuclear physicists have come together there to practice handling the material from the anti-world. Hidden behind a mountain of concrete blocks is the steel tube through which technicians shoot a bundle of several million anti-protons once every one-and-a-half minutes. The scientists decelerate the particles, steer them with the help of electric and magnetic fields and try to shape anti-atoms out of them.
With its relatively modest budget, measured in mere millions, the AD undertaking at CERN tends to be overshadowed by the major projects. To many of the scientists working at the €3 billion LHC, the fabrication of anti-atoms seems more like a charming game. “A little of this beautiful physics also needs to be allowed,” says CERN theoretician John Ellis, with a mixture of arrogance and respect.
Japanese physicist Masaki Hori of the Max Planck Institute of Quantum Optics, near Munich, has managed to fashion bizarre artificial objects out of helium and anti-protons. They have enabled him to measure the mass of the anti-proton. Working in the laser laboratory, Hori and his team are now refining a method with which they will be able to measure mass more accurately than was possible with normal matter. “Then we’ll be writing textbook knowledge,” he says proudly.
Two offices away, Michael Doser is working on another experiment. He wants to measure how the Earth’s gravitational field acts on antimatter. He even hopes to be able to measure how the Moon’s gravity affects anti-atoms.
But Jeffrey Hangst garnered the most attention when he was able to bombard a single anti-atom with microwaves. “We’ve had one breakthrough after another in the last year and a half,” he says. “CERN is very pleased with us.”
He impatiently hurries his team along. They are developing a new anti-atom trap that will also include a window. This will make it possible to irradiate the captives from the anti-world with lasers. Hangst wants the new device to be up and running before the accelerator is shut down for maintenance in the late fall.
But will any of these efforts truly demonstrate that the energy spectrum of anti-hydrogen is different from that of its twin atom made of matter? Is it even possible for an anti-proton to be lighter than a proton? And is it possible that gravity acts differently on matter and antimatter?
Hori, Doser and Hangst know all too well that hardly any of their colleagues would bet on the answers to any of these questions. “If we really find something, it’ll be as if the sun had suddenly rose in the west,” says Hori. Dirac’s hallowed electron equation, at any rate, doesn’t actually permit the kinds of differences that the physicists in the AD building are searching for.
But they don’t allow themselves to be deterred by such objections. “Sometimes you just have to hope for miracles,” says Doser. His colleague Hangst adds: “I love taking risks. Those who only listen to the theoreticians quickly run into difficulties.”
He is alluding to a divide within the community of physicists. In physics, much more so than in other disciplines, a distinction is drawn between two types of researchers. The theorists, acting as heirs of Paul Dirac, attempt to fathom the truth using pure mental power. For the others, the experimental physicists, all that counts is what the instruments say.
Searching for the Theory of Everything
John Ellis is part of the former group. The agile Briton with a white shaman’s beard is an old hand at CERN. For the last 40 years, he has monitored his colleagues’ experiments in the accelerators from his desk, and he managed the theory division for years.
As a young researcher, he looked on as scientists assembled the so-called Standard Model of particle physics, a collection of formulas that summarizes all known laws of the microcosm. He later coined the term “Theory of Everything,” a reference to a distant goal that stimulates many theoreticians in their work: the prospect of eventually finding a sort of global formula that unifies all the laws of nature.
But the search for such an all-encompassing theory proved to be a frustrating business, although it wasn’t for a lack of ideas. On the contrary, a mountain of designs for the world has accumulated on Ellis’s desk over the years, including stacks of articles addressing such topics as spacetime foam and sphalerons, dark matter and 10-dimensional superpartners.
The one thing all of these ideas had in common is that they couldn’t be tested. In their scenarios, the theoreticians increased energy to breathtaking dimensions. Devices with which such phenomena could be studied didn’t exist.
But now, as Ellis and many of his colleagues agree, physics could be at a turning point. With the advent of the LHC, a particle accelerator is finally available that is capable of penetrating into interesting areas.
While the world celebrates the discovery of the Higgs boson, the last building block of the standard model, theoreticians have already started thinking about what happens next. They are now about to venture into the unknown, into realms that can no longer be described with the current laws of nature.
For theoretician Ellis, this is both exciting and disappointing. Just as the era of pure speculation is finally coming to an end, Ellis is reaching retirement age.
He only goes to his office at CERN occasionally nowadays. Dust is beginning to collect on the books on the shelf, and the mountain of paper on his desk is starting to erode.
But Ellis is too active to go completely into retirement. He has just returned from a conference in Ukraine, and he spent the preceding weekend in Tunis, where he brought together young physicists from the northern and southern shores of the Mediterranean. In between, he made a stop in Cambridge to discuss a new project.
If necessary, he puts his ideas to paper while sitting in an airplane or an airport lounge. Ellis is still publishing on an almost weekly basis.
He often addresses the question of where physics could be heading beyond the Standard Model. There are many indications that antimatter could pave the way into the new era.
So far, the formulas of the Standard Model predict almost everything the detectors are measuring. There is only one phenomenon where they fail, however: They cannot explain the whereabouts of antimatter.
To investigate the mystery, Ellis uses his formulas to feel his way into the first one-billionth of a second after the Big Bang. In this earliest period of the universe, he speculates, the laws of nature were quasi frozen in their current state. That was when matter and antimatter parted ways.
The good thing about the LHC is that it accelerates protons strongly enough to achieve energies that were typical during this decisive era. This in turn makes theories that describe these processes verifiable. At the beginning of the year, engineers increased the performance of their super-accelerator even further. Since then, a tsunami of data has swept from the detectors to the computer center. And the more accurately the properties of the Higgs boson can be defined, the clearer will the contours of the new physics become. “We’ll know more by the end of this year,” Ellis promises.
And what if the predictions of the Standard Model are confirmed once again? What if the study of anti-atoms uncovers no differences at all between matter and antimatter?
Ellis wouldn’t be a good theoretician if he weren’t prepared for this eventuality. “Then the course was set even earlier,” he explains. In that case, the fate of the universe must have been decided not in the first billionth but in the first trillionth of a second. “In terms of the theory, this is a huge difference,” says Ellis.
Ellis has already dreamed up scenarios of how all of this could have unfolded. Ghostlike neutrinos apparently play a key role.
Translated from the German by Christopher Sultan