Fundamentally Too Fast

After announcing in September that they had detected neutrinos traveling faster than the speed of light, OPERA researchers immediately set out to replicate their results. On Uncertain Principles, Chad Orzel says they reconfigured the neutrino beam, which originally fired 10,000-nanosecond pulses, “to produce much, much shorter pulses—less than 10ns. And while they’ve only been running this way for a few weeks, they’ve already got 20 neutrino detections from the shorter pulses, and they see exactly the same timing anomaly.” This confirmation rules out problems with the original experimental design, showing that the OPERA results are at least self-consistent. On Starts With a Bang, Ethan Siegel says there could still be a “systematic error in their expected delay calculations, which may be due to something like the atomic clocks, the measurement of the baseline distance, an electronics triggering mishap, or some other mundane reason akin to these.” Independent results from an experiment called MINOS could confirm or contradict OPERA’s findings in two years, but for now we can wonder: why would a subatomic particle exceed Einstein’s speed limit by .0002 percent?

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Leaving Light in the Dust?

Last month, a team of researchers announced that their neutrinos appeared to be travelling faster than the speed of light. Ethan Siegel explains that the mass of a neutrino is “less than one-millionth the mass of the electron, but still not equal to zero” and “should move at a speed indistinguishable from the speed of light.” Meanwhile the OPERA team had to smash 1020 protons just to detect 16,000 neutrinos—and account for every source of delay an uncertainty in their experimental setup. On Uncertain Principles, Chad Orzel explains that the researchers used GPS satellites to measure the 730 kilometer distance between the proton source and the neutrino detector to within 20 centimeters, and synchronize the atomic clocks at each site. Chad writes “superluminal particles that interact with ordinary matter (as neutrinos do, albeit weakly) opens the door to violations of causality—effects happening before the things that caused them, and that sort of thing.” Steinn Sigurðsson writes on Dynamics of Cats, “Well, along with 99.87% of physicists, I am very skeptical,” but adds “a very, very faint possibility is that either relativity is wrong; or, muon neutrinos are weakly tachyonic; or, the neutrino tunneling between flavours is evidence of some funky stringy higher dimensional tunneling, and the geometry is weakly non-3D.” The OPERA team wants to know: can you spot the error?

Unseen Oscillations

On Brookhaven Bits & Bytes, Steve Kettell brings us up to speed on a new research project taking place beneath a mountain in southern China. The object of study is the neutrino, which can “pass through the Earth and through much of the universe without interacting with anything.” Ethan Siegel explains on Starts With a Bang: “Neutrinos only interact gravitationally and through the weak force. They have no electromagnetic interactions.” And because they have no charge, neutrinos are free to pass between the atoms that make up tangible matter. Steve writes that neutrinos from the sun were first detected in the 1960s—but “only one third of the expected number was observed.” With the new detectors at Daya Bay, scientists can compare the number of neutrinos produced by nuclear reactors with the number detected almost two kilometers down the road. The neutrinos lost in between “would indicate that some of our electron antineutrinos had oscillated into tau antineutrinos, which we cannot physically observe.” Such a result would indicate another source of CP violation in nature and increase our understanding of particle physics.