Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

HADES searches for Dark Matter

12.05.2014

Although Dark Energy and Dark Matter appear to constitute over 95 percent of the universe, nobody knows of which particles they are made up.

Astrophysicists now crossed one potential Dark Matter candidate – the Dark Photon or U boson – off the list in top position. This is the result of recent HADES experiments, where researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and from 17 other European institutes try to pin down the nature of Dark Matter. These negative results – recently published in "Physics Letters B" – could even lead to challenges of the Standard Model of particle physics.


HADES at the GSI in Darmstadt/Germany searches for Dark Matter candidates.

3D Rendering: A. Schmah/HADES

The interpretation of current astrophysical observations results in the striking mass-energy budget of matter in the universe: 75% Dark Energy and 20% Dark Matter. Only about 5% of the universe consists of "ordinary", baryonic matter.

Many attempts have been made to explain the nature of Dark Matter. Researchers believe that Dark Matter is comprised by hitherto unknown particles which do not fit into the Standard Model of particle physics.

The Standard Model is a theoretically sound quantum field theory with fundamental matter particles, such as quarks (bound in hadrons, e.g., baryons) and leptons (e.g., electrons and neutrinos), which interact via exchange of force-carrier quanta, called gauge bosons (e.g., photons). Some of these species acquire their masses by the interaction with the Higgs boson.

While evidences for the Higgs boson were found recently at CERN, the Standard Model looks now complete when supplemented by some neutrino masses, and nothing else seems to be needed to understand the wealth of atomic, sub-nuclear and particle physics phenomena. Nevertheless, Dark Matter appears not to be explained by any of the constituents of the Standard Model. This status of the affair has initiated worldwide efforts to search for Dark Matter candidates.

Beyond the Standard Model

Searching a needle in the haystack is simpler: one knows both the wanted object (the needle) and the place (the haystack). In the case of Dark Matter the object is unknown, and the localization, e.g. in galactic halos, is also not constraining the loci of interest. To specify the search goal one can envisage diverse hypothetical candidates, such as certain hypothetical particles beyond the Standard Model, which fulfill requirements qualifying them as constituents of Dark Matter.

Dark Energy drives the presently observed accelerated expansion of the universe. Dark Energy is homogeneously distributed and can be attributed to a cosmological constant or vacuum energy. In extreme cases it may cause, in the future, such a sudden expansion that anything in the universe is disrupted - this would be the Big Rip. Dark Matter, in contrast, is bumpy and is needed to explain the formation of the observed density distribution of visible matter in the evolving universe, evidenced by the hierarchy of structures from (super)clusters of galaxies, galaxies, stars, planets and other compact objects such as meteorites, etc.

Among the lists of candidates of Dark Matter is a hypothetical particle, often dubbed U boson or Dark Photon. These nicknames refer to the underlying theory construction: a second unitary ("U") symmetry allows for quanta which are, in one respect, similar to photons - namely gauge bosons - but in another respect different from photons - namely attributing to these quanta a mass, making them to Dark Photons because of a very weak interaction with normal matter. Very similar to photons the Dark Photons can decay into electron-positron pairs, if they have the proper virtuality. Combining the chain of hypotheses one arrives at a scenario, where an "ordinary" virtual photon converts into a Dark Photon which decays afterwards into an electron-positron pair.

Needle and Haystack

If a Dark Photon or U boson would exist with the assumed properties mentioned above and would have a mass, a certain width and a certain coupling strength to the photon, then the „needle" is specified: a resonance-type signal showing up at an invariant electron-positron mass equal to the U boson mass. The "haystack" is specified too: invariant mass spectra, i.e. electron-positron distributions. A prerequisite is an understanding of the overall shape of these distributions.

Up to now the search for such a signal of a U boson as a candidate for Dark Matter has remained unsuccessful. Together with many other searches for the other candidates of Dark Matter the situations becomes more and more intricate. Cosmology on precision level requires the existence of Dark Matter; however, the various experiments have not found any positive hint. The negative results on the U boson by HADES and other experiments make the hunt for new physics beyond the Standard Model more challenging. For instance, high-precision experiments on the magnetic moment of the muon delivered hints for a discrepancy with predictions by the Standard Model. The discrepancy has been proposed to be resolved by the U boson. But the recently achieved negative search results seem to exclude such an option. This gives the impression that the tension of the Standard Model and cosmological request of extensions as well as small deviations of the Standard Model predictions and data, such as the muon magnetic moment and other observables, is increasing, thus making this frontier of physics very fascinating with high discovery potential.

The HADES collaboration

HADES is an acronym of High-Acceptance Di-Electron Spectrometer. It is an optimized detector system operated by a European collaboration of about hundred physicists at GSI Helmholtzzentrum für Schwerionenforschung/Darmstadt. HADES is aimed at investigating virtual photon signals emitted as electron-positron pairs off compressed nuclear matter to understand the origin of the phenomenon "masses of hadrons" and test it in some detail.

The HADES collaboration has accumulated more than ten billion analyzable events during the last years. The notion "events" means that in collisions of energetic protons with target protons or atomic nuclei or in collisions of atomic nuclei with target nuclei, among other final-state particles, an electron-positron pair could occur. Sources of these pairs are, e.g., unstable hadrons being transiently produced in these collisions. The highly sophisticated apparatus HADES has the capability to select out of a huge background of other particles such electron-positron pairs which can be attributed to primary sources.

Publication: G. Agakishiev et al. (HADES Collaboration), Phys. Lett. B 731, 265 (2014), DOI Link: http://dx.doi.org/10.1016/j.physletb.2014.02.035

Caption: HADES at the GSI in Darmstadt/Germany searches for Dark Matter candidates. 3D Rendering: A. Schmah/HADES

For additional information:

Prof. Dr. Burkhard Kämpfer

Institute of Radiation Physics at HZDR

Phone +49 351 260 3258 | b.kaempfer@hzdr.de

Media contact:

Dr. Christine Bohnet | Press officer
Phone +49 351 260 - 2450 or +49 160 969 288 56

Mail c.bohnet@hzdr.de

Helmholtz-Zentrum Dresden-Rossendorf | Bautzner Landstr. 400 | 01328 Dresden | Germany | www.hzdr.de

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is conducting research in the areas of energy, health, and matter. Since 2011, the HZDR has been a member of the Helmholtz Association, Germany's largest scientific organization. Some 1,000 employees are working at one of four research sites in Dresden, Leipzig, Freiberg, and Grenoble/France – approximately 500 of HZDR employees are scientists.

Dr. Christine Bohnet | Eurek Alert!
Further information:
https://www.hzdr.de/db/Cms?pNid=99&pOid=41693

Further reports about: HZDR Haystack Helmholtz-Zentrum Model Photon collisions hadrons

More articles from Physics and Astronomy:

nachricht Exploring the mysteries of supercooled water
01.03.2017 | American Institute of Physics

nachricht Optical generation of ultrasound via photoacoustic effect
01.03.2017 | American Institute of Physics

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: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

A better way to measure the stiffness of cancer cells

01.03.2017 | Health and Medicine

Exploring the mysteries of supercooled water

01.03.2017 | Physics and Astronomy

Research team of the HAW Hamburg reanimated ancestral microbe from the depth of the earth

01.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>