Antimatter is rare in the universe, and so looking for it is a good way of hunting for exotic phenomena like dark matter.

Another indication that something funny is happening on the dark side of the universe is evident in maps of the cosmic background radiation left over from the Big Bang. Those maps, produced most recently this year by the Wilkinson Microwave Anisotropy Probe satellite, show a haze of what seem to be charged particles hovering around the Milky Way galaxy, according to an analysis by Douglas Finkbeiner of the Harvard-Smithsonian Center for Astrophysics.

Adding to the mix and mystery, the European Space Agency’s Integral satellite detected gamma rays emanating from the center of the Milky Way, suggesting the presence of positrons there, but with much lower energies than Pamela and Dr. Wefel’s experiments have seen.

What all this adds up to, or indeed whether it all adds up to anything at all, depends on which observations you trust and your theoretical presumptions about particle physics and the nature of dark matter. Moreover, efforts to calculate the background level of high-energy particles in the galaxy are beset with messy uncertainties. “The dark matter signal is easy to calculate,” Dr. Kane said. “The background is much harder.”

Dark matter has teased and obsessed astronomers since the 1930s, when the Caltech astronomer Fritz Zwicky deduced that some invisible “missing mass” was required to supply the gravitational glue to hold clusters of galaxies together. The idea became respectable in the 1970s when Vera C. Rubin of the Carnegie Institution of Washington and her collaborators found from studying the motions of stars that most galaxies seemed to be surrounded by halos of dark matter.

The stakes for dark matter go beyond cosmology. The most favored candidates for its identity come from a theory called supersymmetry, which unifies three of the four known forces of nature mathematically and posits the existence of a realm of as-yet-undiscovered particles. They would be so-called wimps  weakly interacting massive particles  which feel gravity and little else, and could drift through the Earth like wind through a screen door. Such particles left over from the Big Bang could form a shadow universe clumping together into dark clouds that then attract ordinary matter.

The discovery of a supersymmetric particle would also be a boost for string theory, the controversial “theory of everything,” and would explicate the nature of a quarter of the universe. But until now, the dark matter particles have mostly eluded direct detection in the laboratory, the exception being a controversial underground experiment called Dama/Libra, for Dark Matter/Large Sodium Iodide Bulk for Rare Processes, under the Italian Alps, where scientists claimed in April to have seen a seasonal effect of a “dark matter wind” as the Earth goes around its orbit.