The existence of exotic hadrons — a type of matter that doesn’t fit within the traditional model of particle physics — has now been confirmed, scientists say.
Hadrons are subatomic particles made up of quarks and antiquarks (which have the same mass as their quark counterparts, but opposite charge), which interact via the “strong force” that binds protons together inside the nuclei of atoms.
Researchers working on the Large Hadron Collider beauty (LHCb) collaboration at CERN (the European Organization for Nuclear Research) in Switzerland — where the elusive Higgs boson particle was discovered in 2012 — announced today (April 14) they had confirmed the existence of a new type of hadron, with an unprecedented degree of statistical certainty.
“We’ve confirmed the unambiguous observation of a very exotic state — something that looks like a particle composed of two quarks and two antiquarks,” study co-leader Tomasz Skwarnicki, a high-energy physicist at Syracuse University in New York said in a statement. The discovery “may give us a new way of looking at strong-[force] interaction physics,” he added.
The Standard Model of particle physics allows for two kinds of hadrons. “Baryons” (such as protons) are made up of three quarks, and “mesons” are made up of a quark- antiquark pair. But since the Standard Model was developed, physicists have predicted the existence of other types of hadrons composed of different combinations of quarks and antiquarks, which could arise from the decay of mesons.
In 2007, a team of scientists called the Belle Collaboration that was using a particle accelerator in Japan discovered evidence of an exotic particle called Z(4430), which appeared to be composed of two quarks and two antiquarks. But some scientists thought their analysis was “naïve” and lacked good evidence, Skwarnicki said.
A few years later, a team known as BaBar used a more sophisticated analysis that seemed to explain the data without exotic hadrons.
“BaBar didn’t prove that Belle’s measurements and data interpretations were wrong,” Skwarnicki said. “They just felt that, based on their data, there was no need to postulate existence of this particle.”
So the original team conducted an even more rigorous analysis of the data, and found strong evidence for the particle.
Now, the LHCb team has studied data from more than 25,000 meson decay events selected from data from 180 trillion proton-proton collisions in the Large Hadron Collider, the world’s largest and most powerful particle accelerator. They analyzed the data using both the Belle and BaBar teams’ methods, and confirmed the particle was both real and an exotic hadron.
The results of the experiment are “the clincher” that such particles do exist, and aren’t just some artifact of the data, Skwarnicki said.
His colleague, Sheldon Stone of CERN, also praised the achievement. “It’s great to finally prove the existence of something that we had long thought was out there,” he said.
On July 4, 2012, scientists around the world waited with bated breath for the announcement that the long-awaited Higgs boson particle had been discovered. The finding — the result of the biggest and most expensive experiment in history — was set to either confirm reigning models of particle physics, or reveal gaps in scientists’ understanding of the universe.
A new documentary follows six scientists during the launch of the machine that made the discovery possible, the Large Hadron Collider (LHC), a gigantic particle accelerator at the European Organization for Nuclear Research (CERN), in Switzerland, as they attempt to recreate the earliest moments of the universe. “Particle Fever” captures the scientists’ sense of excitement and foreboding leading up to the discovery of the Higgs, the particle that explains how other particles get their mass.
“I knew this big event was coming, and I wanted it recorded,” said producer David Kaplan, a physicist at Johns Hopkins University in Baltimore, Md. “I knew it was going to be extremely dramatic scientifically, and also emotionally, for all of my colleagues,” Kaplan told Live Science.
The film, which opens March 5 in New York and March 21 in Washington, D.C., stars a group of theoretical and experimental physicists united by a quest to probe the nature of the universe, using the world’s most powerful particle accelerator. The LHC collides two beams of protons (particles that make up the nuclei of atoms) at near light-speed around the 17 miles (27 kilometers) of the machine’s ring. The collisions produce new particles, which could reveal the composition of space itself.
The film opens during the first test of a single proton beam in September 2008. Viewers meet Fabiola Gianotti, the former spokeswoman for ATLAS, one of the two LHC experiments that detected the Higgs, as well as experimental physicists Monica Dunford and Martin Aleksa, both at ATLAS, who rose to prominence throughout the course of the experiment. Mike Lamont, the LHC’s beam operation leader, also features in the film. Lamont faces the formidable challenge of ensuring the LHC’s successful launch and operation.
But to understand why scientists need the LHC, one first has to understand the hypotheses it is putting to the test.
Supersymmetry vs. multiverse
The Standard Model of particle physics, finalized in the 1970s, seeks to explain the origin of matter and forces in the universe. The model predicts the existence of a few fundamental particles, including the Higgs boson, theorized by British physicist Peter Higgs in 1964. Finding the Higgs confirms the existence of the Higgs field, and this field gives all other particles their mass.
An extension of the Standard Model known as supersymmetry suggests a highly structured and symmetrical universe, in which every particle has a supersymmetric twin that has yet to be discovered. Another, somewhat radical hypothesis suggests the known universe is part of a much larger, chaotic multiverse, in which the laws of physics are random.
The film pits Kaplan and Stanford theorist Savas Dimopoulos, proponents of supersymmetry, against the young Princeton theorist Nima Arkani-Hamed, a supporter of the multiverse idea. The LHC offers the chance to test these hypotheses for the first time. If supersymmetry proves itself, physicists are on the right track. On the other hand, “We may fall off a cliff,” and find that the fundamental laws of physics turn out to be random, Kaplan said.
Biggest experiment in history
The beam test went off successfully in 2008, but a few weeks later, a catastrophic explosion in the facility vented liquid helium, damaging many of the magnets inside the LHC.
“The whole film changed,” said director Mark Levinson, who added he didn’t know how long it would take to fix the damage, and whether the film would have a happy ending. Fortunately, repairs were completed, and the collider was up and running by November 2009.
Fast-forward to July 2012, and the discovery of the Higgs. The particle observed by the LHC confirmed what physicists had long suspected, but also brought up new questions.
Most supersymmetry models predict a Higgs boson with a mass of about 115 gigaelectronvolts, or GeV, whereas multiverse models predict a heavier mass of about 140 GeV. The Higgs observed by the LHC was about 125 GeV — smack in the middle, which doesn’t confirm or rule out either theory. Instead, it merely narrows down the possibilities.
It’s like being lost in the woods, and then getting a hint of the broad direction you should go, Kaplan said, adding, “At least you know which way to start walking.”
In the next step, scientists will collide protons at higher energies, to see if even more particles are created, as predicted by supersymmetry. The LHC was shut down for upgrades in 2013, with plans to reopen it running at twice the power in 2015.
The filmmakers hope “Particle Fever” gives audiences an appreciation of particle physics, and gets them excited about learning more. As Kaplan said, “We want people to come out thinking physics is awesome.”
Editor’s Note: This article was updated at 6:07 p.m. ET, to correct references to untested “theories” to “hypotheses” or “models.”
LONDON — Exotic particles never before detected and possibly teensy extra dimensions may be awaiting discovery, says a physicist, adding that those searching for such newbies should keep an open mind and consider all possibilities.
Such particles are thought to fill gaps in, and extend, the reigning theory of particle physics, the Standard Model, said David Charlton of the University of Birmingham in the United Kingdom, who is also a spokesperson of the ATLAS experiment at the world’s biggest particle accelerator, the Large Hadron Collider (LHC), and one of the experiments that pinpointed the Higgs boson particle thought to explain why other particles have mass.
Charlton addressed an audience of researchers last month at a talk titled “Before, behind and beyond the discovery of the Higgs Boson” here at the Royal Society.
“The questions raised by the discovery of the Higgs boson suggest new physics, and new particles, may be near to hand, at the energies now — and soon — being probed at the LHC,” he said. Such questions, he said, include: why is the Higgs boson so light; and why does the Standard Model have such difficulty explaining physics that occurs at masses higher than that of the Higgs boson, to name a couple.
The LHC, housed in a 17-mile-long (27 kilometers) circular, underground tunnel at CERN near Geneva, Switzerland, smashes protons together at near light speed. The resulting collisions release huge amounts of energy in the form of particles — possibly new, exotic ones.
At the moment, the particle accelerator is switched off so that an upgrade can be made. However, it will start hunting for new particles again in 2015, smashing protons together at its maximum energy of 14 TeV, or terra electron volts.
Before they wake up the LHC from its nap, scientists are busy putting together an extensive program of searches for new particles that could validate one or another extension to the reigning theory of particle physics — the Standard Model.
Because it is impossible to know for certain what these hypothetical particles would be, researchers will look at many and varied collision types, “hunting in numerous ways for deviations in the data from the background expectations from known processes,” said Charlton. (Physicists know what distributions should result from the formation of various known particles, so if they see a deviation from these expectations, they can hypothesize that a new particle has been detected.)
An extension to the Standard Model is necessary to shed light on the remaining mysteries of the universe, such as the nature of dark matter, the elusive particles that are thought to account for about 85 percent of all the matter in the universe.
Many have hailed supersymmetry, a theory that posits every known particle in the universe has a yet-undiscovered and much heavier sister particle, as the main candidate for an extension. However, the LHC’s failure to produce any proof of supersymmetric particles has prompted a number of scientists to look elsewhere for evidence of new physics.
“Supersymmetry is a great idea, but there’s no experimental evidence for it at this stage,” said Charlton. “It’s just one of the possibilities for physics beyond the Standard Model, and it has some elegant math properties so it tends to be favored. But there’s a range of other models that could also help to explain some of the problems that we see with the Standard Model.”
One popular alternative to supersymmetry proposes the idea of extra dimensions.
Scientists suspect extra dimensions exist in space and time; these dimensions are microscopic, proponents say, making them tricky for detectors to pick up. “But as we go to very high energies with the LHC, maybe we’ll start to see evidence of extra dimensions,” said Charlton. Such evidence would come in the form of new particles, or perhaps missing energy as some particles move off in dimensions other than the ones people can see. Such extra dimensions are needed in string theory, which suggests that tiny strings replace sub-atomic particles.
Another idea suggests that the particles that have already been found are not actually fundamental, meaning they have a sub-structure composed of even smaller particles. And then there is string theory, which suggests tiny strings replace subatomic particles.
Searching for ‘something’
But physicists should not simply be searching for evidence to support one theory or another, Charlton said. Rather, it is important “to look at every rare process we can that might be a signal for some new physics showing up. We have to study each one and see if it’s consistent with our expectations.”
If LHC fails to detect any signs of new physics, the only way forward is scaling up to higher-energy collisions and more intense beams. “There could be a model that we haven’t thought of yet,” said Charlton.
And it is this possibility of “something out there that researchers haven’t thought of yet and that would explain all the mysteries” that is the most exciting, said physicist Ben Allanach of the University of Cambridge, adding, “Of course, if I could think of that, I’d be working on that.”
To spot this “something,” physicists must look for high-energy particles in many different ways and many different configurations, and see whether the data is consistent with the expectations, or if there’s something that perhaps isn’t predicted by any of the existing models, Charlton said.
“We really have to try to be as open as possible and try to leave no stone unturned in looking at all the possibilities,” said Charlton.
Science breakthroughs in the past year include the discovery of new planets far beyond Earth’s solar system, the confirmation of an elusive particle and new clues about the evolutionary history of early humans. But science keeps marching on, raising the question: What will next year bring?
An unscientific survey of scientists from a variety of fields yields some predictions — and some ambitious hopes and dreams for 2014.
From discoveries to send the physics world reeling to the search for alien moons, here’s what scientists are wishing for in the new year.
For now, the famous Large Hadron Collider (LHC) on the border of France and Switzerland is quiet, shut down for two years of maintenance and improvements that will make the particle collider stronger than ever when it comes back online in 2015.
But the pace of physics hasn’t slowed. The last of the LHC results from earlier tests are still to come, said Tara Shears, a physicist at the University of Liverpool in the United Kingdom. And other big experiments are underway. In 2014, Shears will watch an experiment at the European Organization for Nuclear Research (CERN) that is investigating antihydrogen, the antimatter component of hydrogen. Antimatter is a material with the same mass as ordinary matter but is made of particles with opposite charges. CERN’s ALPHA experiment seeks to investigate the gravitational interaction between matter and antimatter.
Shears is also intrigued by measurements by the Alpha Magnetic Spectrometer (AMS), which is aboard the International Space Station. In April 2013, scientists announced the AMS had detected an excess of high-energy positrons, an antimatter particle that is essentially the opposite of an electron. Finally, Shears is hoping for more knowledge about neutrinos, neutral subatomic particles, from a new measurement chamber at Fermilab in Illinois.
Most of all, Shears hopes for a measurement that disrupts the Standard Model of physics, an explanation of how tiny particles interact. So far, discoveries such as the confirmation of the Higgs boson particle all match the Standard Model’s predictions, which is disappointing because the model can’t explain all the weirdness of the universe, Shears said.
“I hope for a stealth measurement, a Trojan horse that makes the Standard Model crumble ’round it,” Shears told LiveScience.
Other mysteries are lurking in the far reaches of the universe, where new observations are increasingly revealing planets far outside the bounds of this solar system. Researchers have found more than 800 of these exoplanets, but they’re most excited about the dozen or so that have the potential to be habitable.
The past year turned up a few potential “Earth 2.0s,” said Abel Mendez, a planetary scientist and director of the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo. But the worlds still need to be confirmed as such. Mendez has ambitious hopes for 2014. He’d like to see a calculation of the density of a potentially habitable exoplanet, he told LiveScience. He’d also like to see an Earth-like planet discovered closer to Earth, which would allow for better characterizations than can be made about far-flung worlds.
Mendez’s final dream for the new year? The discovery of an exomoon. So far, scientists have not been able to detect whether the exoplanets they’ve found have their own satellites, but experience in this solar system suggests they should.
“These three goals are very ambitious for just next year, but would represent a big advancement for exoplanets science,” Mendez said.
Back on Earth, 2014 could be a strong year for medical science, said bioethicist Arthur Caplan of the New York University Langone Medical Center. Caplan predicts major advances in diagnosing Alzheimer’s disease using computed tomography (CT) scanning or magnetic resonance imaging (MRI). He also hopes to see stem cells— cells that can differentiate to become many types of tissue — take their place in doctors’ bags of tricks.
“2014 could be the year in which regenerative medicine using stem cells shows its first real breakthrough for treating intractable diseases such as spinal-cord injury,” Caplan told LiveScience.
Caplan has high hopes for medical ethics in the new year, too. Electronic forms for informed consent should start to replace paper consent forms, he said, which will make it easier to quiz patients to be sure they really understand the procedures they’re agreeing to undergo. He also expects patients to challenge the norm of donated tissue samples being used in research; currently, any monetary benefit from these donations goes to researchers or drug developers rather than to the donors who made the work possible.
Finally, Caplan said, 2014 should be the year in which the Food and Drug Administration (FDA) makes guidelines for at-home genetics testing. There are rumblings that the regulatory agency is turning its attention to these new tests. In November, California-based genetics testing company 23andMe received a FDA warning to stop marketing its mail-in genetics tests, which can tell buyers their genetic risk of certain diseases. The company has temporarily suspended those tests while it works with the FDA.
Caplan expects that when the FDA releases new regulations, it will change the way at-home genetics testing operates.
“No existing companies using current methods will meet those regulations, but they will begin to add more counseling and information on test accuracy in order to do so,” he said.
New will meet old in 2014 in the field of paleontology, where technology is making it increasingly easier to investigate fragile fossils.
“The use of technology in the recovery and analysis of fossils is blossoming,” said Matthew Mossbrucker, director of the Morrison Natural History Museum in Morrison, Colo. “For example, fine-scale CT scanning and virtual preparation can accelerate the process of examining fossils that were thought to be inaccessible — either because they are locked in hard rock or perhaps too delicate to prepare mechanically.”
Researchers can even use new 3D-printing technology to take digital scans of fossils and turn them into perfect 3D copies to be studied and displayed. Mossbrucker and his colleagues plan to use CT scanning to analyze delicate fossils trapped in hard sandstone in the coming year, he said.
“These methods will not replace traditional fossil preparation, but will be another arrow in our quiver,” Mossbrucker told LiveScience.
Robotics and biomechanics researcher Andy Ruina of Cornell University calls his 2014 wishes “rather pedestrian” — that is, he wants to see robots act more like pedestrians.
The challenge is to create legged automatons that can walk on uneven surfaces, as humans do, using about the same amount of energy that humans do, Ruina told LiveScience. So far, Boston Dynamics’ humanoid robot Atlas can handle rough terrain, but only while tethered to a power supply.
Ruina would also like to see a theory of robot control that explains how living creatures move and handle objects while also providing blueprints on how to get a machine to make the same movements.
Jekanthan Thangavelautham, a roboticist at Arizona State University has similar dreams of an graceful robot that could manage greyhound-like speeds outdoors — in the range of 43 mph (70 km/h), that is. He’d also like to see a fully 3D-printed robot, as well as more robots put to more practical uses. The military, for example, could start using robotic exoskeletons in the field to give soldiers a boost of strength for carrying heavy packs or lifting armaments.