Timing Glitches Dog Neutrino Claim

IN FOCUS NEWS However, if they could be coaxed in a dish to chemotherapy, women who have gone through slow down women’s biological clocks. “Even if make eggs that could successfully be used for premature menopause, or even those experi- you could gain an additional five years of ovar- in vitro fertilization (IVF), it would change the encing normal ageing. Tilly says that follow-up ian function, that would cover most women face of assisted reproduction. studies have confirmed that OSCs exist in the affected by IVF,” notes Tilly. ■ “That’s a huge ‘if’,” admits Tilly. But, he con- ovaries of women well into their 40s. 1. White, Y. A. R. et al. Nature Med. http://dx.doi. tinues, it could mean an unlimited supply of In addition, growing eggs from OSCs in the org/10.1038/nm.2669 (2012). eggs for women who have ovarian tissue that lab would allow scientists to screen for hor- 2. Zou, K. et al. Nature Cell Biol. 11, 631–636 (2009). still hosts OSCs. This group could include can- mones or drugs that might reinvigorate these 3. Johnson, J., Canning, J., Kaneko, T., Pru, J. K. & Tilly, cer patients who have undergone sterilizing cells to keep producing eggs in the body and J. L. Nature 428, 145–150 (2004). TIMING TROUBLE experiment. The initial result suggested that the Two possible sources of error may have aected the results of the GPS receiver neutrinos were reaching the detector 60 nano- OPERA experiment, which measures the arrival time of neutrinos and timing seconds faster than the speed of light would speeding through Earth from CERN to Gran Sasso. system allow. Both potential errors would affect the neutrinos’ arrival time, as measured by OPERA’s master clock (see ‘Timing trouble’). The first is a Global Positioning System (GPS) satellite faulty connection at the point at which the light CERN Gran Sasso 8.3-km from a fibre-optic cable brings a synchronizing Geneva, National bre-optic Global Positioning System (GPS) signal into the Switzerland Laboratory cable L’Aquila, Italy Possible signal master clock. The fault could have delayed the delay in GPS GPS signal, causing the master clock to run slow connection and thus causing the neutrinos’ travel time to (shortens time- of-ight result) appear shorter than it actually was. “It’s a subtle effect,” says Autiero, and one that was evident only when the team exam- Possible mis- timing due to OPERA ined many measurements of signals passing internal oscillator master through the connection. Tests of the timing Neutrino ight path (increases time- clock of-ight result) system turned up a second, opposing effect: an oscillator within the master clock that keeps time between the arrivals of synchronization OPERA detector signals was running fast. That would have 730.5 km timing systems made the neutrinos’ travel time seem longer. The collaboration says that it has not yet worked out the magnitude of these effects. PHYSICS Autiero says that because of the high profile of the result and the possibility of rumours and leaks, the collaboration wanted to disclose the potential errors promptly. The OPERA team Timing glitches plans to correct the faults and repeat the experiment after CERN’s neutrino beam is switched on again in March, following a winter break. Two independent checks of the measure- dog neutrino claim ment are also being considered. One, at Japan’s Tokai to Kamioka (T2K) neutrino experiment, would still be valuable despite the doubt cast on Team admits to possible errors in faster-than-light finding. the OPERA data, but may now prove harder to fund, says international co-spokesman Chang Kee Jung, a physicist at Stony Brook University BY EUGENIE SAMUEL REICH To others, the revelation shows that the in New York. But another, the Main Injector OPERA team went public too soon with its Neutrino Oscillation Search (MINOS) experi- s it an epic blunder or a textbook demon- claim that neutrinos from CERN, the Euro- ment, which fires neutrinos from Fermilab in stration of how science should work? To pean particle-physics laboratory near Geneva Batavia, Illinois, to an underground detector some physicists, the OPERA (Oscillation in Switzerland, were flouting Albert Einstein’s in northern Minnesota, will proceed, at a cost IProject with Emulsion-tracking Apparatus) absolute limit on the speed of light as they trav- of about US$500,000. “It’s never a bad idea to collaboration deserves credit for disclosing elled the 730 kilometres to the OPERA detector have multiple measurements,” says MINOS possible errors in its paradigm-challenging at the underground Gran Sasso National Labo- co-spokesman Rob Plunkett. measurement of neutrinos travelling faster ratory near L’Aquila, Italy. “I find it embarrass- Jorge Páramos, a physicist at the Higher Tech- than light. “I think we did the right thing to ing,” says Luca Stanco of the National Institute nical Institute in Lisbon, says that the admis- continue to investigate,” says Dario Autiero of Nuclear Physics in Padova, Italy, an OPERA sions by OPERA point to an honest mistake, of the Institute of Nuclear Physics of Lyons member who initially refused to sign a paper albeit one that should have been avoided. “The in France, who presented the original results about the result. “Maybe we should have been putative origin of the systematic error reflects and notes that the collaboration had spent more cautious and done more checks.” the innards of the experiment — something that six months checking its result before its On 23 February, OPERA team members should have been checked exhaustively before announcement last September. reported two possible sources of error in the any public announcement,” he says. ■ 1 MARCH 2012 | VOL 483 | NATURE | 17 © 2012 Macmillan Publishers Limited. 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