News blog

Two WIMP-ish detections of dark matter

Researchers may have detected signals indicating the presence of dark matter in the form of Weakly Interacting Massive Particles, or WIMPs.

If this sounds familiar, it’s probably because the news of these WIMPs first surfaced at the end of last year (see: ‘Dark-matter’ events spotted).

Now in this week’s Science, physicists write up the two candidates, possible WIMPs caught in the experiment’s germanium and silicon crystals, which are chilled to nearly absolute zero (–273.15 ºC). When a WIMP strikes one of the crystals, it should trigger vibrations that raise the temperature of the detector very slightly; it should also create a small charge on the crystal’s surface. Comparing the size and timing of the two signals can help determine whether or not they were caused by WIMPs.

If confirmed, it would mark the end of a decades-long search for the mysterious particles thought to make up as much as 85% of matter in the Universe.

But most agree that the signals are not statistically significant enough to be attributed to dark matter rather than to conventional particles. Team scientists think that there is a 25% chance that both events might be false-positives caused by background radiation.

“Either we had a statistical fluctuation in our background or it could be that these two events are evidence of dark matter but there weren’t enough of them to be sure,” says corresponding author Jodi Cooley from Southern Methodist University in Dallas (BBC). “We can’t rule them out as being a signal but we can’t conclude that they are a signal.”

Collaborators of the Cryogenic Dark Matter Search (CDMS II) have been looking for WIMPs 700 meters below ground at the Soudan Underground Laboratory in Minnesota since 2003. “It’s a very difficult situation,” Cooley says (BBC). "In some ways I feel we’ve been very unlucky.”

“Many people believe we are extremely close – not just us, but other experiments,” says CDMS II collaborator Tarek Saab (press release). “It is expected or certainly hoped that in the next five years or so, someone will see a clear signal.”

Comments

Comments are closed.