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 SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

nachricht New survey hints at exotic origin for the Cold Spot
26.04.2017 | Royal Astronomical Society

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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Scientist invents way to trigger artificial photosynthesis to clean air

26.04.2017 | Materials Sciences

Ammonium nitrogen input increases the synthesis of anticarcinogenic compounds in broccoli

26.04.2017 | Agricultural and Forestry Science

SwRI-led team discovers lull in Mars' giant impact history

26.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>