AN EXPERIMENT in openness has fallen at the first hurdle, as physicists at the Pierre Auger Observatory in Argentina have reversed their policy of public discussion, shortly after collecting their initial round of results.
The publicly funded collaboration originally decided to make data from the experiment available on its website. But the information is now being moved to a private site after fears it might be interpreted as hinting that the highest energy cosmic rays, the phenomenon Auger was set up to investigate, do not exist.
Cosmic rays are energetic particles that bombard us from space. If our current understanding is correct, particles with energies above 1020 electronvolts should be absorbed by photons on their way to Earth, and never reach us. However several experiments have claimed to see cosmic rays above this threshold, called the 鈥淕ZK cut-off鈥�, sparking a decades-long debate about their possible origin.
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The Auger observatory has been funded by agencies in 15 countries to answer this question. When completed, the $54-million array of water tanks and telescopes should find the sources of ultra-high-energy cosmic rays by collecting the showers of particles that are scattered downward as each cosmic-ray particle strikes the atmosphere. 鈥淭his is the one experiment with the statistics to resolve the GZK controversy,鈥� says Auger spokesman Alan Watson. About 10 per cent of the detector is now running and has logged between 2000 and 3000 events.
Until last week, any member of Auger could post analysis or data from the experiment on the group鈥檚 public website. 鈥淲e got comments from outside the collaboration and there was some advantage in that,鈥� says Auger spokesman Hans Bl眉mer. But early postings on the first results show no sign of rays above the cut-off.
Not enough data has been collected yet to show whether these cosmic rays exist. But these postings prompted the collaboration to start moving information to a protected site. 鈥淭he risk of misunderstanding was increasing,鈥� says Bl眉mer. Auger is currently applying for funding to make up for $10 million that had been promised but never materialised, and is jumpy about any hint that it is on a wild-goose chase.
鈥淭hey worry some scientists could conclude Auger has not detected a super GZK particle,鈥� says one insider unhappy about the clampdown. Pierre Billoire of the Orsay Linear Accelerator in France, who has been told he cannot now post his own analysis, is also uneasy about the decision. 鈥淚t is a restriction of our individual rights so the collaboration can form a coherent view,鈥� he told 快猫短视频.
In January, an independent study by John Bahcall of the Institute for Advanced Study at Princeton and Eli Waxman at the Weizmann Institute in Israel argued that the GZK cut-off was real, and that experiments claiming to have seen particles beyond it had overestimated their energies (Physics Letters B, vol 556, p 1). 鈥淲e knew our paper would be unwelcome, because lots of groups were using 鈥榯he mysterious absence of the GZK cut-off鈥� as motivation for their experiments,鈥� says Bahcall. 鈥淲e underestimated the intensity of that feeling.鈥�
Instead of releasing data as planned, Auger will now present selected 鈥渆vent highlights鈥� to demonstrate that the detector is working. The move brings Auger back into line with other high-energy physics institutes, none of whom releases raw data. Even though the public funds the research, 鈥渢he obligation is to publish results, not raw data,鈥� says Martin Grunewald, chairman of the Electroweak Working Group at CERN, Geneva. David Plane of CERN鈥檚 Opal Collaboration agrees. 鈥淚 wouldn鈥檛 like to have a completely open procedure where individuals could post their results before the collaboration has had a chance to scrutinise them,鈥� he says.
Bahcall agrees that publishing data before it has been checked 鈥渃ould cause confusion鈥�. But he argues that costly labs doing research that other groups do not have the facilities to carry out have a duty to release data outside scientific papers, in a form that other researchers can analyse. 鈥淚t would be good to have an 鈥榠nterpretation-neutral鈥� way of releasing the data, so that people not in the collaboration can ask different questions of the data,鈥� he says.