Dark Matter Detected By Experiment On International Space Station

A team of scientists say they have detected and measured an excess of positrons in the cosmic ray flux, marking what is likely the first observation of dark matter.

The results come after 22 months of data collected by the Alpha Magnetic Spectrometer (AMS), a $2 billion piece of antimatter-hunting experiment on the International Space Station.

The AMS is the most powerful and sensitive particle spectrometer ever deployed in space. It has collected an enourmous amount of data, more than 25 billion particle events, which were used in an in-depth analysis. 

Of great interest in the data collected is an abnormal "bump" in the spectrum of positrons.

The excess of antimatter or positrons has been observed for more than 20 years and aroused much interest, according to Samuel Ting who led the research. He said AMS is the first experiment to probe in detail in the nature of this excess with its high sensitivity and precision.

"The data will have thousands of explanations," said Ting in a webcast presentation of the research, "and we offer one of them."

In a detailed presentation of the AMS data Ting stopped just short of saying the AMS experiment detected dark matter because there is still a one percent margin of error in the experiment.

"These results are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations," a statement from CERN said.

"As the most precise measurement of the cosmic ray positron flux to date, these results show clearly the power and capabilities of the AMS detector," said Ting. "Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin." Among the 25 billion recorded particle events, the AMS gathered data on 400,000 positrons with energies between 0.5 Gev and 350 GeV. This represents the largest collection of antimatter particles recorded in space.

"We have observed many new phenomena in the positron spectrum," he said. "Soon, the origin of this excess will be understood."

Dark matter is one of the great mysteries of the Universe. Though it cannot be seen,  is thought to account for as much as 25 percent of the Universe's mass-engery balance. 

"The AMS result is a great example of the complementarity of experiments on Earth and in space," said CERN Director General Rolf Heuer in a statement. "Working in tandem, I think we can be confident of a resolution to the dark matter enigma sometime in the next few years."