Synopsis: Still in the Dark

A search for gamma rays from galaxies near the Milky Way allows researchers to tighten the bounds on the annihilation cross sections of candidate dark matter particles.
Synopsis figure
NASA

WIMPs—weakly interacting massive particles—are one of the leading candidates for dark matter. Theory predicts they may annihilate when they collide with each other, releasing gamma rays either directly or as the WIMPs decay through a cascade of intermediate states. Researchers working with the Large Area Telescope (LAT) onboard the orbiting Fermi Gamma-Ray Space Telescope have looked for such signals in places with copious dark matter and have published their results in Physical Review D after four years of observations. While no out-of-the-ordinary gamma rays were detected that could definitively point to dark matter, the team was able to place better bounds on annihilation cross sections.

The LAT researchers analyzed gamma rays from near the Milky Way, observing 25 dwarf satellite galaxies known to contain large amounts of dark matter (as concluded from the way the stars move in the gravity field). The dark matter abundance of such galaxies, combined with their proximity and the absence of large gamma-ray backgrounds, make them one of the most promising detection targets. Since 2008, LAT has been collecting gamma-ray data at energies from 20 mega-electron-volts to over 300 giga-electron-volts. In looking for possible signals, the team considered numerous standard-model annihilation channels (electron-positron, muon-antimuon, and so on) each expected to yield gamma rays with characteristic energy spectra.

While the researchers found no dark matter signal, they were able to calculate the maximum cross section for WIMP annihilation, deriving new limits that, for some dark matter models, are a factor of 2 stronger than existing ones. But as researchers peer into more dwarf galaxies and other dark-matter-rich regions of the Universe, there is still hope for dark matter detection. – David Voss


Announcements

More Announcements »

Subject Areas

Particles and FieldsAstrophysics

Previous Synopsis

Soft Matter

Biocompatible Carbon Carriers

Read More »

Next Synopsis

Quantum Information

Quantum Legos

Read More »

Related Articles

Synopsis: Pentaquark Discovery Confirmed
Particles and Fields

Synopsis: Pentaquark Discovery Confirmed

New results from the LHCb experiment confirm the 2015 discovery that quarks can combine into groups of five. Read More »

Synopsis: Searching for Majorana Neutrinos
Particles and Fields

Synopsis: Searching for Majorana Neutrinos

The KamLAND-Zen collaboration has run the most sensitive search to date for a radioactive decay that could reveal whether neutrinos are Majorana fermions. Read More »

Viewpoint: Hunting the Sterile Neutrino
Particles and Fields

Viewpoint: Hunting the Sterile Neutrino

A search for sterile neutrinos with the IceCube detector has found no evidence for the hypothetical particles, significantly narrowing the range of masses that a new kind of neutrino could possibly have. Read More »

More Articles