New cosmic ray data still allows for dark matter possibility

New measurements of cosmic ray electrons by the PAMELA spacecraft have left open the door for an observation of dark matter but are still consistent with no dark matter signal. Although the measurements of the cosmic ray electrons are consistent with no new sources of electrons, such as dark matter annihilation, the electron and positron data is better fit with some kind of additional source. What that is remains unclear at this time.

The electron energy spectrum measured by PAMELA and other modern instruments. Some of the wiggles in the curves have been interpreted as signs of dark matter by some scientists. However, that interpretation is not conclusive.

The electron energy spectrum measured by PAMELA and other modern instruments. Some of the wiggles in the curves have been interpreted as signs of dark matter by some scientists. However, that interpretation is not conclusive.

The measurement by PAMELA covers a greater range of energies for electrons than any other experiment so far and extends its upper limits on energy significantly. Previous PAMELA data had produced a bump in the spectrum at higher energies which could have been indicative of dark matter.

The team fit the data with a conventional model of cosmic ray propagation (involving no dark matter) and found that it is consistent with the PAMELA data. However, if they assume there is some extra component of cosmic electrons, they get an improved fit to the positron data that they also measure.

If scientists assume there is an extra source of electrons and positron cosmic rays, they get a better fit with their data.

If scientists assume there is an extra source of electrons and positron cosmic rays, they get a better fit with their data.

Those extra electrons could potentially come from dark matter annihilation but there could also be effects from inhomogeneities in cosmic ray arrival and factors like motion around the Sun. So any extra electrons might or might not be from dark matter. At this time, it’s too soon to tell what the extra electrons might be, or even if they exist, but there it looks like a puzzle waiting just on the edge of our ability to measure.

Ref: Phys. Rev. Lett. 106, 201101 (2011)

Posted May 19th, 2011 in Uncategorized.

One comment:

  1. stephen mann:

    Dark matter, if it exists, will be proven in accelerators.

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