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Neutrinos point to a new reality
enrico sacchetti
SPECIAL REPORT / faster than light
The speed limit was smashed at Italy’s OPERA detector
6 | NewScientist | 1 October 2011
For daily news stories, visit newscientist.com/news
Neutrinos point to a new reality Rather than breaking physics, we may have got our first glimpse of extra dimensions, says Lisa Grossman
Dario Autiero of the Institute of Nuclear Physics in Lyon, France, a member of the OPERA collaboration: the distance between the labs, the time the neutrinos left CERN, and the time they arrived at Gran Sasso. But actually measuring those times and distances to the accuracy needed to detect nanosecond differences is no easy task. The OPERA collaboration spent three years chasing down every source of error they could imagine (see illustration, page 8) before Autiero made the result public in a seminar at CERN on 23 September. Physicists grilled Autiero for an hour after his talk to ensure the team had considered details like the curvature of the Earth, the tidal effects of the moon and the general relativistic effects of having two clocks at different heights (gravity slows time so a clock closer to Earth’s surface runs a tiny bit slower).
INFN
SUBATOMIC particles have broken the “The OPERA universe’s fundamental speed limit, or team spent so it was reported last week. The speed three years of light is the ultimate limit on travel chasing down in the universe, and the basis for every source Einstein’s special theory of relativity, of error they so if the finding stands up to scrutiny, could imagine” does it spell the end for physics as we know it? The reality is less simplistic and far more interesting. “People were saying this means Einstein is wrong,” says physicist Heinrich Päs of the Technical University of Dortmund in Germany. “But that’s not really correct.” Instead, the result could be the first evidence for a reality built out of extra dimensions. Future historians of science may regard it not as the moment we abandoned Einstein and broke physics, but rather as the point at which our view of space vastly expanded, from three dimensions to four, or more. “This may be a physics revolution,” says Thomas Weiler at Vanderbilt University in Nashville, Tennessee, who has devised theories built on extra dimensions. “The famous words ‘paradigm shift’ are used too often and tritely, but they might be relevant.” The subatomic particles – neutrinos – seem to have zipped faster than light from CERN, near Geneva, Switzerland, to the OPERA detector at the Gran Sasso lab near L’Aquila, Italy. It’s a conceptually simple result: neutrinos making the 730-kilometre journey arrived 60 nanoseconds earlier than they would have if they were travelling at light speed. And it relies on three seemingly simple measurements, says
They were impressed. “I want to congratulate you on this extremely beautiful experiment,” said Nobel laureate Samuel Ting of the Massachusetts Institute of Technology after Autiero’s talk. “The experiment is very carefully done, and the systematic error carefully checked.” Most physicists still expect some sort of experimental error to crop up and explain the anomaly, mainly because it contravenes the incredibly successful law of special relativity which holds that the speed of light is a constant that no object can exceed. The theory also leads to the famous equation E = mc2. Hotly anticipated are results from other neutrino detectors, including T2K in Japan and MINOS at Fermilab in Illinois, which will run similar experiments and confirm the results or rule them out (See “Higgs bosons are out, neutrinos are in”, page 9). In 2007, the MINOS experiment searched for faster-than-light neutrinos but didn’t see anything statistically significant. The team plans to reanalyse its data and upgrade the detector’s stopwatch. “These are the kind of things that we have to follow through, and make sure that our prejudices don’t get in the way of discovering something truly fantastic,” says Stephen Parke of Fermilab. In the meantime, suggests Sandip Pakvasa of the University of Hawaii, let’s suppose the OPERA result is real. If the experiment is tested and replicated and the only explanation is faster-thanlight neutrinos, is E = mc2 done for? Not necessarily. In 2006, Pakvasa, 1 October 2011 | NewScientist | 7
SPECIAL REPORT / faster than light Päs and Weiler came up with a model that allows certain particles to break the cosmic speed limit while leaving special relativity intact. “One can, if not rescue Einstein, at least leave him valid,” Weiler says. The trick is to send neutrinos on a shortcut through a fourth, thus-farunobserved dimension of space, reducing the distance they have to travel. Then the neutrinos wouldn’t have to outstrip light to reach their destination in the observed time. In such a universe, the particles and forces we are familiar with are anchored to a four-dimensional membrane, or “brane”, with three dimensions of space and one of time. Crucially, the brane floats in a higher dimensional space-time called the bulk, which we are normally completely oblivious to. The fantastic success of special relativity up to now, plus other cosmological observations, have led physicists to think that the brane might be flat, like a sheet of paper. Quantum fluctuations could make it ripple and roll like the surface of the ocean, Weiler says. Then, if neutrinos can break free of the brane, they might get from one point on it to another by dashing through the bulk, like a flying fish taking a shortcut between the waves (see illustration, above). This model is attractive because it offers a way out of one of the biggest theoretical problems posed by the OPERA result: busting the apparent speed limit set by neutrinos detected pouring from a supernova in 1987.
Mistake, or extradimensional shortcut? OPERA reports neutrinos making a 730km journey 60 nanoseconds faster than if they had travelled at light speed OPTION ONE: Experimental error – but errors accounted for so far can’t explain the extraordinary findings Neutrinos are produced by smashing protons into a graphite target to produce pions. They travel down a 1-kilometre tunnel and decay to produce neutrinos When exactly did the neutrinos leave CERN? Electronic delays in the timing system that records when protons arrive at the graphite target introduce uncertainty
ERROR: 5ns
Where exactly the pions decay is also unknown
ERROR: 0.2ns
CERN Geneva
8 | NewScientist | 1 October 2011
ERROR: 0.67ns
DISTANCE TRAVELLED ~730km
OPERA Gran Sasso
Other errors take the total to 7.4ns
OPTION TWO: The neutrinos got there in the reported time by taking a shortcut available if there are extra dimensions
~730km
CERN Geneva
DISTANCE TRAVELLED <730km
As stars explode in a supernova, “The particles most of their energy streams out as might travel neutrinos. These particles hardly ever like flying fish interact with matter (see “A neutrino taking a walks into a bar…”, below). That means shortcut they should escape the star almost between the immediately, while photons of light waves” will take about 3 hours. In 1987, trillions of neutrinos arrived at Earth 3 hours before the dying star’s light caught up. If the neutrinos were travelling as fast
A neutrino walks into a bar… “…We don’t allow faster-than-light neutrinos in here,” says the barman. A neutrino walks into a bar… As reports spread of subatomic particles moving faster than light and potentially travelling through time, such gags were born. But this apparently hasty motion is not the only strange thing about neutrinos. With a neutral charge and nearly zero mass, neutrinos are the shadiest of particles, rarely interacting with ordinary matter and slipping through our bodies, buildings and the Earth at a rate of
Measuring the distance the neutrinos travel is difficult because of the position of the Gran Sasso lab, which lies inside a mountain and is invisible to GPS. However, the distance can still be calculated to within 20cm
trillions per second. Every so often, they crash into an atom to produce a signal that allows us to detect them. Their stealth, however, belies their potential importance. Take extra dimensions. Most particles come in two varieties: ones that spin clockwise and ones that spin anticlockwise. Neutrinos are the only ones that seem to just spin anticlockwise. Some theorists say this is evidence for extra dimensions, which could host the “missing”, right-handed neutrinos. Unseen right-handed neutrinos
may also account for dark matter – the 80 per cent of all matter needed to stop galaxies from flying apart. The idea is that this variety is much heavier than the other, so could provide the requisite gravity. Another strange thing about neutrinos is that they can change their “flavour”. Recent experiments suggest there may be differences between the way that antineutrinos and neutrinos flip, which might in turn explain how an imbalance of matter and antimatter arose in the early universe. Chelsea Whyte
Quantum fluctuations cause normally flat space-time to ripple. This makes an otherwise hidden, extra dimension available to high-energy neutrinos OPERA Gran Sasso
as those going from CERN to OPERA, they should have arrived in 1982. OPERA’s neutrinos were about 1000 times as energetic as the supernova’s neutrinos, though. And Pakvasa and colleagues’ model calls for neutrinos with a specific energy that makes them prefer tunnelling through the bulk to travelling along the brane. If that energy is around 20 gigaelectronvolts – and the team don’t yet know that it is – “then you expect large effects in the OPERA region, and small effects at the supernova energies,” Pakvasa says. He and Päs are meeting next week to work out the details. The flying fish shortcut isn’t available to all particles. In the language of string theory, a mathematical model some physicists hope will lead to a comprehensive “theory of everything”, most particles are represented by tiny vibrating strings whose ends are permanently stuck to the brane. One of the only exceptions is the theoretical “sterile neutrino”, represented by a closed loop of string. These are also the only type of neutrino thought capable of escaping the brane. Neutrinos are known to switch back
For daily news stories, visit newscientist.com/news
fred ullrich
and forth between their three observed types (electron, muon and tau neutrinos), and OPERA was originally designed to detect these shifts. In Pakvasa’s model, the muon neutrinos produced at CERN could have transformed to sterile neutrinos midflight, made a short hop through the bulk, and then switched back to muon before reappearing on the brane. So if OPERA’s results hold up, they could provide support for the existence of sterile neutrinos, extra dimensions and perhaps string theory. Such theories could also explain why gravity is so weak compared with the other fundamental forces. The theoretical particles that mediate gravity, known as gravitons, may also be closed loops of string that leak off into the bulk. “If, in the end, nobody sees anything wrong and other people reproduce OPERA’s results, then I think it’s evidence for string theory, in that string theory is what makes extra dimensions credible in the first place,” Weiler says. Meanwhile, alternative theories are likely to abound. Weiler expects papers to appear in a matter of days or weeks. Even if relativity is pushed aside, Einstein has worked so well for so long that he will never really go away. At worst, relativity will turn out to work for most of the universe but not all, just as Newton’s mechanics work until things get extremely large or small. “The fact that Einstein has worked for 106 years means he’ll always be there, either as the right answer or a lowenergy effective theory,” Weiler says. n
Fieldnotes Fermilab, Illinois
Higgs bosons are out, neutrinos are in David Shiga
MINOS aims to catch super-speedy particles at the Soudan mine
ROGER DIXON gestures, bringing his hand alarmingly close to the big red button that has the power to shut down one of the world’s most powerful particle accelerators forever. “It’s already hooked up,” he says, in response to my nervous questions. We are standing in a room full of blinking displays and control panels at Fermi National Laboratory (Fermilab), which nestles among cornfields outside Chicago. Dixon, who is in charge of the smooth running of the accelerator, the Tevatron, pulls his hand back. Once king, the Tevatron is due to shut down on 30 September as it can no longer compete with the energies achieved by the Large Hadron Collider (LHC) at CERN near Geneva, Switzerland. “It is being superseded,” admits Fermilab director Pier Oddone. For years, Fermilab hoped the Tevatron would find the Higgs boson, the particle thought to endow all others with mass. It has not, and that task has now passed to the LHC. Instead the Tevatron will likely be remembered most for its discovery in 1995 of the top quark, the last of the six quarks in the standard model of particle physics to be seen. But just as the Higgs spotlight moves away from Fermilab, another, potentially equally exciting particle may thrust the lab into the limelight again. Last week, the OPERA experiment rocked the foundations of physics when it reported subatomic particles called neutrinos apparently breaking the light-speed barrier (see main story, page 6). As it turns out, Fermilab’s existing neutrino experiment, MINOS, is well suited to confirming or ruling out this bizarre observation. MINOS fires neutrino beams of an energy similar to those detected at OPERA to a detector in the Soudan mine, 800 kilometres away in Minnesota. Its first task will be to update a 2007 search for faster-than-light neutrinos, which didn’t throw up anything statistically significant, using more recent data. That could be completed in six months, says MINOS collaborator Jenny Thomas of University College London. Meanwhile, the next
incarnation, MINOS Plus, will have new GPS sensors, atomic clocks and detectors to record neutrino arrival time with a precision of 2 nanoseconds. This could deliver results as early as 2014. In the absence of the Tevatron, neutrino physics will soon receive the bulk of Fermilab’s resources, and focus on more than pure speed. A short drive from the Tevatron control room is a symbol of this shift – a black, brick-shaped structure the size of a school bus. It is part of the Nova experiment, which will begin in 2013. Nova will study neutrinos’ ability to morph, or “oscillate”, from one type to another, looking for potential differences in the way neutrinos and their antimatter counterparts oscillate, which MINOS results hint at. In the early universe, the differences might have created a preponderance of matter over antimatter that would account for the universe’s current composition. “Neutrinos have been a source of big surprises in the past,” says Oddone. “I don’t think we’re going to understand particle physics until we understand neutrinos.” Fermilab might yet come back with an accelerator to rival the LHC. In a brightly lit laboratory with gleaming white floors, I glimpse what looks like a stack of silver doughnuts. Made of pure niobium, this bumpy tube will be superconducting when chilled to near absolute zero in a bath of liquid helium. If 16,000 tubes can be lined end to end, they will form an accelerator called the International Linear Collider. The electrons and positrons it smashes together will have a collision energy of 1 teraelectronvolt. That’s a fraction of the LHC’s 7 TeV, but if the LHC discovers the Higgs, say, the ILC should be able to measure its mass and other properties more precisely. As the Tevatron’s last day approaches, few here seem sentimental. Fermilab helped make the Tevatron obsolete, after all, by building some of the LHC’s magnets and contributing to one of its two main detectors. “It’s a bittersweet moment,” says Oddone. “It has been quite a wonderful life for the Tevatron. But you don’t stay at the leading edge unless you build new things.” Additional reporting by Chelsea Whyte n 1 October 2011 | NewScientist | 9
SPECIAL REPORT / faster than light
The speed limit was smashed at Italy’s OPERA detector
6 | NewScientist | 1 October 2011
For daily news stories, visit newscientist.com/news
Neutrinos point to a new reality Rather than breaking physics, we may have got our first glimpse of extra dimensions, says Lisa Grossman
Dario Autiero of the Institute of Nuclear Physics in Lyon, France, a member of the OPERA collaboration: the distance between the labs, the time the neutrinos left CERN, and the time they arrived at Gran Sasso. But actually measuring those times and distances to the accuracy needed to detect nanosecond differences is no easy task. The OPERA collaboration spent three years chasing down every source of error they could imagine (see illustration, page 8) before Autiero made the result public in a seminar at CERN on 23 September. Physicists grilled Autiero for an hour after his talk to ensure the team had considered details like the curvature of the Earth, the tidal effects of the moon and the general relativistic effects of having two clocks at different heights (gravity slows time so a clock closer to Earth’s surface runs a tiny bit slower).
INFN
SUBATOMIC particles have broken the “The OPERA universe’s fundamental speed limit, or team spent so it was reported last week. The speed three years of light is the ultimate limit on travel chasing down in the universe, and the basis for every source Einstein’s special theory of relativity, of error they so if the finding stands up to scrutiny, could imagine” does it spell the end for physics as we know it? The reality is less simplistic and far more interesting. “People were saying this means Einstein is wrong,” says physicist Heinrich Päs of the Technical University of Dortmund in Germany. “But that’s not really correct.” Instead, the result could be the first evidence for a reality built out of extra dimensions. Future historians of science may regard it not as the moment we abandoned Einstein and broke physics, but rather as the point at which our view of space vastly expanded, from three dimensions to four, or more. “This may be a physics revolution,” says Thomas Weiler at Vanderbilt University in Nashville, Tennessee, who has devised theories built on extra dimensions. “The famous words ‘paradigm shift’ are used too often and tritely, but they might be relevant.” The subatomic particles – neutrinos – seem to have zipped faster than light from CERN, near Geneva, Switzerland, to the OPERA detector at the Gran Sasso lab near L’Aquila, Italy. It’s a conceptually simple result: neutrinos making the 730-kilometre journey arrived 60 nanoseconds earlier than they would have if they were travelling at light speed. And it relies on three seemingly simple measurements, says
They were impressed. “I want to congratulate you on this extremely beautiful experiment,” said Nobel laureate Samuel Ting of the Massachusetts Institute of Technology after Autiero’s talk. “The experiment is very carefully done, and the systematic error carefully checked.” Most physicists still expect some sort of experimental error to crop up and explain the anomaly, mainly because it contravenes the incredibly successful law of special relativity which holds that the speed of light is a constant that no object can exceed. The theory also leads to the famous equation E = mc2. Hotly anticipated are results from other neutrino detectors, including T2K in Japan and MINOS at Fermilab in Illinois, which will run similar experiments and confirm the results or rule them out (See “Higgs bosons are out, neutrinos are in”, page 9). In 2007, the MINOS experiment searched for faster-than-light neutrinos but didn’t see anything statistically significant. The team plans to reanalyse its data and upgrade the detector’s stopwatch. “These are the kind of things that we have to follow through, and make sure that our prejudices don’t get in the way of discovering something truly fantastic,” says Stephen Parke of Fermilab. In the meantime, suggests Sandip Pakvasa of the University of Hawaii, let’s suppose the OPERA result is real. If the experiment is tested and replicated and the only explanation is faster-thanlight neutrinos, is E = mc2 done for? Not necessarily. In 2006, Pakvasa, 1 October 2011 | NewScientist | 7
SPECIAL REPORT / faster than light Päs and Weiler came up with a model that allows certain particles to break the cosmic speed limit while leaving special relativity intact. “One can, if not rescue Einstein, at least leave him valid,” Weiler says. The trick is to send neutrinos on a shortcut through a fourth, thus-farunobserved dimension of space, reducing the distance they have to travel. Then the neutrinos wouldn’t have to outstrip light to reach their destination in the observed time. In such a universe, the particles and forces we are familiar with are anchored to a four-dimensional membrane, or “brane”, with three dimensions of space and one of time. Crucially, the brane floats in a higher dimensional space-time called the bulk, which we are normally completely oblivious to. The fantastic success of special relativity up to now, plus other cosmological observations, have led physicists to think that the brane might be flat, like a sheet of paper. Quantum fluctuations could make it ripple and roll like the surface of the ocean, Weiler says. Then, if neutrinos can break free of the brane, they might get from one point on it to another by dashing through the bulk, like a flying fish taking a shortcut between the waves (see illustration, above). This model is attractive because it offers a way out of one of the biggest theoretical problems posed by the OPERA result: busting the apparent speed limit set by neutrinos detected pouring from a supernova in 1987.
Mistake, or extradimensional shortcut? OPERA reports neutrinos making a 730km journey 60 nanoseconds faster than if they had travelled at light speed OPTION ONE: Experimental error – but errors accounted for so far can’t explain the extraordinary findings Neutrinos are produced by smashing protons into a graphite target to produce pions. They travel down a 1-kilometre tunnel and decay to produce neutrinos When exactly did the neutrinos leave CERN? Electronic delays in the timing system that records when protons arrive at the graphite target introduce uncertainty
ERROR: 5ns
Where exactly the pions decay is also unknown
ERROR: 0.2ns
CERN Geneva
8 | NewScientist | 1 October 2011
ERROR: 0.67ns
DISTANCE TRAVELLED ~730km
OPERA Gran Sasso
Other errors take the total to 7.4ns
OPTION TWO: The neutrinos got there in the reported time by taking a shortcut available if there are extra dimensions
~730km
CERN Geneva
DISTANCE TRAVELLED <730km
As stars explode in a supernova, “The particles most of their energy streams out as might travel neutrinos. These particles hardly ever like flying fish interact with matter (see “A neutrino taking a walks into a bar…”, below). That means shortcut they should escape the star almost between the immediately, while photons of light waves” will take about 3 hours. In 1987, trillions of neutrinos arrived at Earth 3 hours before the dying star’s light caught up. If the neutrinos were travelling as fast
A neutrino walks into a bar… “…We don’t allow faster-than-light neutrinos in here,” says the barman. A neutrino walks into a bar… As reports spread of subatomic particles moving faster than light and potentially travelling through time, such gags were born. But this apparently hasty motion is not the only strange thing about neutrinos. With a neutral charge and nearly zero mass, neutrinos are the shadiest of particles, rarely interacting with ordinary matter and slipping through our bodies, buildings and the Earth at a rate of
Measuring the distance the neutrinos travel is difficult because of the position of the Gran Sasso lab, which lies inside a mountain and is invisible to GPS. However, the distance can still be calculated to within 20cm
trillions per second. Every so often, they crash into an atom to produce a signal that allows us to detect them. Their stealth, however, belies their potential importance. Take extra dimensions. Most particles come in two varieties: ones that spin clockwise and ones that spin anticlockwise. Neutrinos are the only ones that seem to just spin anticlockwise. Some theorists say this is evidence for extra dimensions, which could host the “missing”, right-handed neutrinos. Unseen right-handed neutrinos
may also account for dark matter – the 80 per cent of all matter needed to stop galaxies from flying apart. The idea is that this variety is much heavier than the other, so could provide the requisite gravity. Another strange thing about neutrinos is that they can change their “flavour”. Recent experiments suggest there may be differences between the way that antineutrinos and neutrinos flip, which might in turn explain how an imbalance of matter and antimatter arose in the early universe. Chelsea Whyte
Quantum fluctuations cause normally flat space-time to ripple. This makes an otherwise hidden, extra dimension available to high-energy neutrinos OPERA Gran Sasso
as those going from CERN to OPERA, they should have arrived in 1982. OPERA’s neutrinos were about 1000 times as energetic as the supernova’s neutrinos, though. And Pakvasa and colleagues’ model calls for neutrinos with a specific energy that makes them prefer tunnelling through the bulk to travelling along the brane. If that energy is around 20 gigaelectronvolts – and the team don’t yet know that it is – “then you expect large effects in the OPERA region, and small effects at the supernova energies,” Pakvasa says. He and Päs are meeting next week to work out the details. The flying fish shortcut isn’t available to all particles. In the language of string theory, a mathematical model some physicists hope will lead to a comprehensive “theory of everything”, most particles are represented by tiny vibrating strings whose ends are permanently stuck to the brane. One of the only exceptions is the theoretical “sterile neutrino”, represented by a closed loop of string. These are also the only type of neutrino thought capable of escaping the brane. Neutrinos are known to switch back
For daily news stories, visit newscientist.com/news
fred ullrich
and forth between their three observed types (electron, muon and tau neutrinos), and OPERA was originally designed to detect these shifts. In Pakvasa’s model, the muon neutrinos produced at CERN could have transformed to sterile neutrinos midflight, made a short hop through the bulk, and then switched back to muon before reappearing on the brane. So if OPERA’s results hold up, they could provide support for the existence of sterile neutrinos, extra dimensions and perhaps string theory. Such theories could also explain why gravity is so weak compared with the other fundamental forces. The theoretical particles that mediate gravity, known as gravitons, may also be closed loops of string that leak off into the bulk. “If, in the end, nobody sees anything wrong and other people reproduce OPERA’s results, then I think it’s evidence for string theory, in that string theory is what makes extra dimensions credible in the first place,” Weiler says. Meanwhile, alternative theories are likely to abound. Weiler expects papers to appear in a matter of days or weeks. Even if relativity is pushed aside, Einstein has worked so well for so long that he will never really go away. At worst, relativity will turn out to work for most of the universe but not all, just as Newton’s mechanics work until things get extremely large or small. “The fact that Einstein has worked for 106 years means he’ll always be there, either as the right answer or a lowenergy effective theory,” Weiler says. n
Fieldnotes Fermilab, Illinois
Higgs bosons are out, neutrinos are in David Shiga
MINOS aims to catch super-speedy particles at the Soudan mine
ROGER DIXON gestures, bringing his hand alarmingly close to the big red button that has the power to shut down one of the world’s most powerful particle accelerators forever. “It’s already hooked up,” he says, in response to my nervous questions. We are standing in a room full of blinking displays and control panels at Fermi National Laboratory (Fermilab), which nestles among cornfields outside Chicago. Dixon, who is in charge of the smooth running of the accelerator, the Tevatron, pulls his hand back. Once king, the Tevatron is due to shut down on 30 September as it can no longer compete with the energies achieved by the Large Hadron Collider (LHC) at CERN near Geneva, Switzerland. “It is being superseded,” admits Fermilab director Pier Oddone. For years, Fermilab hoped the Tevatron would find the Higgs boson, the particle thought to endow all others with mass. It has not, and that task has now passed to the LHC. Instead the Tevatron will likely be remembered most for its discovery in 1995 of the top quark, the last of the six quarks in the standard model of particle physics to be seen. But just as the Higgs spotlight moves away from Fermilab, another, potentially equally exciting particle may thrust the lab into the limelight again. Last week, the OPERA experiment rocked the foundations of physics when it reported subatomic particles called neutrinos apparently breaking the light-speed barrier (see main story, page 6). As it turns out, Fermilab’s existing neutrino experiment, MINOS, is well suited to confirming or ruling out this bizarre observation. MINOS fires neutrino beams of an energy similar to those detected at OPERA to a detector in the Soudan mine, 800 kilometres away in Minnesota. Its first task will be to update a 2007 search for faster-than-light neutrinos, which didn’t throw up anything statistically significant, using more recent data. That could be completed in six months, says MINOS collaborator Jenny Thomas of University College London. Meanwhile, the next
incarnation, MINOS Plus, will have new GPS sensors, atomic clocks and detectors to record neutrino arrival time with a precision of 2 nanoseconds. This could deliver results as early as 2014. In the absence of the Tevatron, neutrino physics will soon receive the bulk of Fermilab’s resources, and focus on more than pure speed. A short drive from the Tevatron control room is a symbol of this shift – a black, brick-shaped structure the size of a school bus. It is part of the Nova experiment, which will begin in 2013. Nova will study neutrinos’ ability to morph, or “oscillate”, from one type to another, looking for potential differences in the way neutrinos and their antimatter counterparts oscillate, which MINOS results hint at. In the early universe, the differences might have created a preponderance of matter over antimatter that would account for the universe’s current composition. “Neutrinos have been a source of big surprises in the past,” says Oddone. “I don’t think we’re going to understand particle physics until we understand neutrinos.” Fermilab might yet come back with an accelerator to rival the LHC. In a brightly lit laboratory with gleaming white floors, I glimpse what looks like a stack of silver doughnuts. Made of pure niobium, this bumpy tube will be superconducting when chilled to near absolute zero in a bath of liquid helium. If 16,000 tubes can be lined end to end, they will form an accelerator called the International Linear Collider. The electrons and positrons it smashes together will have a collision energy of 1 teraelectronvolt. That’s a fraction of the LHC’s 7 TeV, but if the LHC discovers the Higgs, say, the ILC should be able to measure its mass and other properties more precisely. As the Tevatron’s last day approaches, few here seem sentimental. Fermilab helped make the Tevatron obsolete, after all, by building some of the LHC’s magnets and contributing to one of its two main detectors. “It’s a bittersweet moment,” says Oddone. “It has been quite a wonderful life for the Tevatron. But you don’t stay at the leading edge unless you build new things.” Additional reporting by Chelsea Whyte n 1 October 2011 | NewScientist | 9