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High-flying cosmic-ray detector offers hints but no results yet

When Samuel Ting, a physicist at the Massachusetts Institute of Technology in Cambridge, got up to give his plenary talk at the opening session of the American Physical Society’s spring meeting in Atlanta on 31 March, the vast hotel ballroom was close to standing-room only. Ting is not only a Nobel laureate, but he is also the principal investigator and prime mover of the Alpha Magnetic Spectrometer (AMS): the hugely controversial, US$1.5-billion cosmic-ray detector that has been riding on the International Space Station since its launch last May (see Nature 455, 854–857; 2008). If AMS works as advertised, it could detect positrons from the self-annihilation of the mysterious particles comprising dark matter, thus providing the first solid clue as to what those particles are. It might also see anti-helium nuclei that were created right after the Big Bang, thus shedding fresh light on why matter is so much more common than antimatter.

But Ting is a famously meticulous man, willing to spend enormous amounts of time on checking and cross-checking his experiments before announcing his results. He spent almost all of his 30-minute talk describing the AMS and going over the multitudinous tests his team has conducted to prove that the AMS is working as planned in the weightless, airless, sun-blasted environment of space.

Along the way, however, Ting did drop a few tantalizing hints. The AMS is working very well, he said. It has registered some 14 billion cosmic-ray events in ten months — far more than expected. And it has seen high-energy positrons: Ting showed four examples with energies ranging from 205 to 424 gigaelectronvolts.

“Hopefully within a year,” was his reply when he was asked about when results would be announced — “and as late as I can. We don’t want to announce preliminary results.”

Photo credit: NASA


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