Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Physicists set strongest limit on mass of dark matter

24.11.2011
Brown University physicists have set the strongest limit for the mass of dark matter, the mysterious particles believed to make up nearly a quarter of the universe. The researchers report in Physical Review Letters that dark matter must have a mass greater than 40 giga-electron volts. The distinction is important because it casts doubt on recent results from underground experiments that have reported detecting dark matter.

If dark matter exists in the universe, scientists now have set the strongest limit to date on its mass.


View of the universe from NASA's Fermi Gamma-ray Space Telescope. Credit: Koushiappas and Geringer-Sameth/Brown University

In a paper to be published on Dec. 1 in Physical Review Letters (available in pdf), Brown University assistant professor Savvas Koushiappas and graduate student Alex Geringer-Sameth report that dark matter must have a mass greater than 40 giga-electron volts in dark-matter collisions involving heavy quarks. (The masses of elementary particles are regularly expressed in term of electron volts.) Using publicly available data collected from an instrument on NASA’s Fermi Gamma-ray Space Telescope and a novel statistical approach, the Brown pair constrained the mass of dark matter particles by calculating the rate at which the particles are thought to cancel each other out in galaxies that orbit the Milky Way galaxy.

“What we find is if a particle’s mass is less than 40 GeV, then it cannot be the dark matter particle,” Koushiappas said.

The observational measurements are important because they cast doubt on recent results from dark matter collaborations that have reported detecting the elusive particle in underground experiments. Those collaborations – DAMA/LIBRA, CoGeNT and CRESST – say they found dark matter with masses ranging from 7 to 12 GeV, less than the limit determined by the Brown physicists.

“If for the sake of argument a dark matter particle’s mass is less than 40 GeV, it means the amount of dark matter in the universe today would be so much that the universe would not be expanding at the accelerated rate we observe,” Koushiappas said, referring to the 2011 Nobel prize in physics that was awarded for the discovery that the expansion of the universe is accelerating.

The Fermi-LAT Collaboration, an international scientific collaboration, arrived at similar results, using a different methodology. The Brown and Fermi-LAT collaboration papers will be published in the same issue of Physical Review Letters.

Physicists believe everything that can be seen — planets, stars, galaxies and all else — makes up only 4 percent of the universe. Observations indicate that dark matter accounts for about 23 percent of the universe, while the remaining part is made up of dark energy, the force believed to cause the universe’s accelerated expansion. The problem is dark matter and dark energy do not emit electromagnetic radiation like stars and planets; they can be “seen” only through their gravitational effects. Its shadowy profile and its heavy mass are the main reasons why dark matter is suspected to be a weakly interacting massive particle (WIMP), which makes it very difficult to study.

What physicists do know is that when a WIMP and its anti-particle collide in a process known as annihilation, the debris spewed forth is comprised of heavy quarks and leptons. Physicists also know that when a quark and its anti-quark sibling annihilate, they produce a jet of particles that includes photons, or light.

Koushiappas and Geringer-Sameth in essence reversed the annihilation chain reaction. They set their sights on seven dwarf galaxies which observations show are full of dark matter because their stars’ motion cannot be fully explained by their mass alone. These dwarf galaxies also are largely bereft of hydrogen gas and other common matter, meaning they offer a blank canvas to better observe dark matter and its effects. “There’s a high signal-to-noise ratio. They’re clean systems,” Koushiappas said.

The pair analyzed gamma ray data collected over the last three years by the Fermi telescope to measure the number of photons in the dwarf galaxies. From the number of photons, the Brown researchers were able to determine the rate of quark production, which, in turn, allowed them to establish constraints on the mass of dark matter particles and the rate at which they annihilate.

“This is the first time that we can exclude generic WIMP particles that could account for the abundance of dark matter in the universe,” Koushiappas said.

Geringer-Sameth developed the statistical framework to analyze the data and then applied it to observations of the dwarf galaxies. “This is a very exciting time in the dark matter search, because many experimental tools are finally catching up to long-standing theories about what dark matter actually is,” said Geringer-Sameth, from Croton-on-Hudson, N.Y. “We are starting to really put these theories to the test.”

The National Science Foundation funded the research.

Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews, and maintains an ISDN line for radio interviews. For more information, call (401) 863-2476.

Richard Lewis | EurekAlert!
Further information:
http://www.brown.edu

Further reports about: Fermi Fermi-LAT Milky Way dark energy dark matter gravitational effect

More articles from Physics and Astronomy:

nachricht Physicists Design Ultrafocused Pulses
27.07.2017 | Universität Innsbruck

nachricht CCNY physicists master unexplored electron property
26.07.2017 | City College of New York

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Physicists Design Ultrafocused Pulses

Physicists working with researcher Oriol Romero-Isart devised a new simple scheme to theoretically generate arbitrarily short and focused electromagnetic fields. This new tool could be used for precise sensing and in microscopy.

Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to...

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

Programming cells with computer-like logic

27.07.2017 | Life Sciences

Identified the component that allows a lethal bacteria to spread resistance to antibiotics

27.07.2017 | Life Sciences

Malaria Already Endemic in the Mediterranean by the Roman Period

27.07.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>