By DENNIS OVERBYE
Published: April 17, 2008
A team of Italian and Chinese physicists on Wednesday renewed a controversial claim that they had detected the mysterious dark matter particles that astronomers say swaddle the galaxies in halos and direct the evolution of the universe.
The team, called Dama, from “DArk MAtter,” and led by Rita Bernabei of the University of Rome, has maintained since 2000 that a yearly modulation in the rate of flashes in a detector nearly a mile underneath the Gran Sasso mountain in Italy is the result of the Earth’s passage through a “wind” of dark matter particles as it goes around the Sun. Other groups of hunters of dark matter have just as consistently failed to find any evidence of the putative particles.
At a meeting in Venice, Dr. Bernabei reported that a new, bigger experiment named Dama/Libra had now observed the same modulation. “No other experiment whose result can be directly compared in a model-independent way is available so far,” she said. The findings increase the chances that the modulation is real, outside dark matter experts say.
Dark matter has taunted astronomers and physicists ever since the astronomer Fritz Zwicky of the California Institute of Technology
pointed out in the 1930s that clusters of galaxies appear to be missing enough visible matter to hold them together gravitationally. Speculation has centered on the possibility that the dark matter consists of hypothetical elementary particles left over from the Big Bang — so-called WIMPs, or weakly interacting massive particles, that are immune to most forces of nature and so can pass through us and the Earth like ghosts.