Even a meeting of elite minds at Europe's top particle physics lab couldn't reconcile faster-than-light neutrinos with the laws of physics. However, a paper on the speeding neutrinos has been accepted for publication and the first preliminary results from a comparable experiment are out.
"For the moment, there is no explanation that works," says physicist Ignatios Antoniadis, who helped to organise the meeting at CERN near Geneva, Switzerland, last Friday. It was three weeks to the day after physicists in the OPERA collaboration at Gran Sasso, Italy, announced that neutrinos travelling from CERN had apparently moved faster than light.
Frantic calculation, speculation and debate have followed in the wake of the announcement. The meeting's goal was to "review the situation and discuss whether it is possible [that neutrinos broke the speed of light]" , says Antoniadis.
The biggest challenge yet to the OPERA result comes from Nobel laureate Sheldon Glashow and his Boston University colleague Andrew Cohen in a paper posted online a few weeks ago.
Physical Review Letters has agreed to publish the paper, making it the first scientific journal to accept work on the OPERA result.
In the paper, Glashow and Cohen point out that if neutrinos can travel faster than light, then when they do so they should sometimes radiate an electron paired with its antimatter equivalent – a positron – through a process called Cerenkov radiation, which is analogous to a sonic boom. Each electron-positron pair should carry away a large chunk of the neutrinos' energy: Cohen and Glashow calculated that at the end of the experiment, the neutrinos should have had energies no higher than about 12 gigaelectronvolts. But OPERA saw plenty of neutrinos with energies upwards of 40 GeV.
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