fricklemanzz76E41F
Banned
Last night, replying to a global surge in interest, the OPERA experiment released a paper that describes the experiments that seem to show neutrinos traveling faster than the rate of light. And today, CERN broadcast a live convention in which one of the work's authors described the content of the paper. Both these emphasized the point of our initial coverage : figuring out whether anything is traveling beyond the speed of light requires extraordinarily correct measurements of time and distance, and the OPERA team has made an intensive effort to make its work as accurate as possible.
As a spokesman for the MINOS neutrino experiment told Ars yesterday, there are 3 potential sources of boo boo in the timing measurements : distance screw ups, time-of-flight errors, and errors in the timing of neutrino production. The overwhelming majority of both the paper and the lecture were dedicated to debating how these gaffes were reduced ( the particular identifying of the neutrinos was only a little portion of the paper ).
Neutrinos are produced employing a proton beam from one of the accelerators that feeds them into the LHC. The protons hit a fixed target and produce infirm particles that rot, releasing a neutrino. The protons move close to, but not at the speed of light, as do the unstable pions ; both of these effects were accounted for. The timing of the protons and structure of the 2 bunches of them used in these experiments isn't even, either, so that the researchers created a profile of the proton bunch. They also compensated for the timing of the kicker magnet that pushes the bunch out of the accelerator and added detectors that registered them passing thru the hardware to get a more clear sense of their timing.
Similar work went into the detector side, where the time between an actual neutrino event and the signal propagating thru the hardware and to a field programmable gate array ( FPGA ) where it was processed was estimated at about 50ns ( the neutrinos only arrived 60ns early, so that 50ns is a substantial fragment of the total ). But the boo boo in their guesstimate was only 2.3ns, as measured by shining a picosecond UV laser on the detector.
Distance travelled created its own problems. The positions of the hardware were measured thru GPS, which usually doesn't provide the type of precision needed for this work. But the labs did multiple examples of the GPS signals, threw out bad ones, compensated for the results of the Earth's iononsphere, and more. Then, solely to check their work, they'd a commercial company come in and perform an independent research. The end result was a measurement delicate enough to register both the steady change due to continental drift , as well as a 7cm jump caused by a tremor.
Then, the timing of all the events had to be synchronized. At each site, the group put a cesium-based atomic clock, and synchronized it with the GPS signal. Then, they sent a portable atomic clock between the facilities to test. They then ran photons through a fiber optic cable between them, just to make certain.
The ultimate result is that the OPERA team doesn't see any clear problems in its measurements. All of the mistakes, when added up, shouldn't be in a position to account for anything near to the 60ns gap between the neutrinos ' arrival and the speed of light. The greatest difference between their speed and that of light is terribly statistically heavy, and the neutrino information itself looks glorious. The team has recorded over Sixteen thousand events now, and the profile of events over a period really closely matches the anatomy of the proton bunches that created them.
But that doesn't mean that this presentation is the final word on the subject. There are a lot of potential sources of mistake they know aboutthe paper's table lists 12 of them. Small errors in each of these could add up to something more important than their total gaffe. Then there are the classic unknown unknowns. The writers have attempted to think of everything, but it's unclear that they can.
The audience at the convention was already thinking about other sources. As an example, GPS signals don't essentially penetrate down to the where any of the hardware is, meaning that this system has to trace the hardware's motion a bit indirectly. This led one audience member to proffer "if this is a real measurement, drill a bloody hole." The speaker indicated that commercial drilling hardware isn't correct enough to go direct from the surface to the detectors, which are kept that deep to filter most cosmic rays briefly the solution would create another error.
The other reason that many are voicing skepticism are past measurements of neutrino speeds obtained from supernovae. Since these are so stupendously distant, the small signal seen here would be hugethe neutrinos should arrive roughly four years in front of the photons. Other experiments on Earth also advised insignificant differences. One possible reason for this is the energy of the neutrinos, since OPERA uses much higher energy than the different sources. But the paper indicates that's not likely to be the situation, since the writers saw the same signal with both 10 and 40GeV neutrinos.
In the meantime, the physics community will be looking thru the paper, attempting to spot unaccounted for sources of boo boo. There are two other similar neutrino detectors in useT2K and MINOSand they'll definitely be looking into working out the timing of their hardware with the same sort of care OPERA has.
The theorists Nevertheless, will without doubt be having a wild time. It will be a bit before anyone has the opportunity to test these results independently, giving theorists a chance to try to reconcile fast neutrinos with the rest of physics till then.
Home Warranty
As a spokesman for the MINOS neutrino experiment told Ars yesterday, there are 3 potential sources of boo boo in the timing measurements : distance screw ups, time-of-flight errors, and errors in the timing of neutrino production. The overwhelming majority of both the paper and the lecture were dedicated to debating how these gaffes were reduced ( the particular identifying of the neutrinos was only a little portion of the paper ).
Neutrinos are produced employing a proton beam from one of the accelerators that feeds them into the LHC. The protons hit a fixed target and produce infirm particles that rot, releasing a neutrino. The protons move close to, but not at the speed of light, as do the unstable pions ; both of these effects were accounted for. The timing of the protons and structure of the 2 bunches of them used in these experiments isn't even, either, so that the researchers created a profile of the proton bunch. They also compensated for the timing of the kicker magnet that pushes the bunch out of the accelerator and added detectors that registered them passing thru the hardware to get a more clear sense of their timing.
Similar work went into the detector side, where the time between an actual neutrino event and the signal propagating thru the hardware and to a field programmable gate array ( FPGA ) where it was processed was estimated at about 50ns ( the neutrinos only arrived 60ns early, so that 50ns is a substantial fragment of the total ). But the boo boo in their guesstimate was only 2.3ns, as measured by shining a picosecond UV laser on the detector.
Distance travelled created its own problems. The positions of the hardware were measured thru GPS, which usually doesn't provide the type of precision needed for this work. But the labs did multiple examples of the GPS signals, threw out bad ones, compensated for the results of the Earth's iononsphere, and more. Then, solely to check their work, they'd a commercial company come in and perform an independent research. The end result was a measurement delicate enough to register both the steady change due to continental drift , as well as a 7cm jump caused by a tremor.
Then, the timing of all the events had to be synchronized. At each site, the group put a cesium-based atomic clock, and synchronized it with the GPS signal. Then, they sent a portable atomic clock between the facilities to test. They then ran photons through a fiber optic cable between them, just to make certain.
The ultimate result is that the OPERA team doesn't see any clear problems in its measurements. All of the mistakes, when added up, shouldn't be in a position to account for anything near to the 60ns gap between the neutrinos ' arrival and the speed of light. The greatest difference between their speed and that of light is terribly statistically heavy, and the neutrino information itself looks glorious. The team has recorded over Sixteen thousand events now, and the profile of events over a period really closely matches the anatomy of the proton bunches that created them.
But that doesn't mean that this presentation is the final word on the subject. There are a lot of potential sources of mistake they know aboutthe paper's table lists 12 of them. Small errors in each of these could add up to something more important than their total gaffe. Then there are the classic unknown unknowns. The writers have attempted to think of everything, but it's unclear that they can.
The audience at the convention was already thinking about other sources. As an example, GPS signals don't essentially penetrate down to the where any of the hardware is, meaning that this system has to trace the hardware's motion a bit indirectly. This led one audience member to proffer "if this is a real measurement, drill a bloody hole." The speaker indicated that commercial drilling hardware isn't correct enough to go direct from the surface to the detectors, which are kept that deep to filter most cosmic rays briefly the solution would create another error.
The other reason that many are voicing skepticism are past measurements of neutrino speeds obtained from supernovae. Since these are so stupendously distant, the small signal seen here would be hugethe neutrinos should arrive roughly four years in front of the photons. Other experiments on Earth also advised insignificant differences. One possible reason for this is the energy of the neutrinos, since OPERA uses much higher energy than the different sources. But the paper indicates that's not likely to be the situation, since the writers saw the same signal with both 10 and 40GeV neutrinos.
In the meantime, the physics community will be looking thru the paper, attempting to spot unaccounted for sources of boo boo. There are two other similar neutrino detectors in useT2K and MINOSand they'll definitely be looking into working out the timing of their hardware with the same sort of care OPERA has.
The theorists Nevertheless, will without doubt be having a wild time. It will be a bit before anyone has the opportunity to test these results independently, giving theorists a chance to try to reconcile fast neutrinos with the rest of physics till then.
Home Warranty
Last edited by a moderator:
