An international team of scientists has for the first time computed the masses of one of the most important constituents of matter - protons and neutrons. The tool which contributed the most to this calculation: JUGENE, a supercomputer at the Jülich research cerntre in Germany.
The elaborate simulations confirm a fundamental theory of physics, quantum chromodynamics. The team has reported their findings in the Nov. 21 issue of Science magazine.
Matter is made of atoms, atoms in turn are made of a nucleus of protons and neutrons and a cloud of orbiting electrons. “More than 99.9 % of the mass of the visible universe comes from protons and Neutrons”, says Zoltan Fodor, a Hungarian physicist, affiliated with Wuppertal University, who was the leader of the project. These particles, commonly referred to as "nucleons" by physicists, are made of three quarks.
The masses of these three quarks, however, only add up to a few percent of the total mass of a nucleon - so where does the mass of the nucleons come from? The answer is provided by Einsteins famous formula E=mc2: energy and mass are equivalent and more than 95 % of the nucleon mass originates from the motion energy of quarks and particles they exchange.
The three quarks inside a nucleon are bound together by the so-called strong interaction, a force that - as the name suggests - is very strong but only relevant at tiny distances. For quite some time, physicists have been using a theoretical description of this interaction, quantum chromodynamics. “In principle it should be possible to calculate the mass of the nucleons from quantum chromodynamics”, says Fodor.
These calculations are extremely complicated. Similarly to the electromagnetic interaction, which is transmitted by photons – small quanta of light – the strong interaction is transmitted by gluons. However, contrary to photons, the gluons interact with each other. This self-interaction is responsible for the fact that the interaction is so strong that quarks do not appear alone, but only as bound states of two or three quarks. This self-interaction makes the theoretical determination of the nucleon mass so complex, that so far it seemed to be beyond our possibilities to carry out this calculation.
Thanks to the JUGENE supercomputer at Forschungszentrum Juelich Fodor and his colleagues were able to solve the problem, and for the first time the managed to treat the strong interaction for larger distances. They calculated the masses protons, neutrons and several other particles, which are bound states of quarks. JUGENE can perform 180 billion operations in a second, a performance which makes it the number 1 supercomputer in Europe.The calculation of Fodor and his colleagues uses a four-dimensional lattice and the solve the equations of quantum chromodynamics on the sites of this lattice.
After that they reduce the distance between the lattice sites in several steps, which brings the result closer and closer to reality, to our continuous space-time. “This is one of the most CPU-demanding calculation known to mankind”, says Fodor.
As a result the researchers obtained the mass of the nucleon, in complete agreement with the experimentally measured value. “This result indicates that quantum chromodynamics is the proper theory of the strong interaction”, concludes Fodor.
The researcher futrther explains, that “the origin of the vast majority of the visible mass is therefore settled”. There are however further riddles yet to be solved. A large fraction of the total mass of the universe is dark and its composition is yet unknown. “We do not know yet what dark matter is and how it gets its mass.”
Cutting edge research for the industries of tomorrow – DFKI and NICT expand cooperation
21.03.2017 | Deutsches Forschungszentrum für Künstliche Intelligenz GmbH, DFKI
Molecular motor-powered biocomputers
20.03.2017 | Technische Universität Dresden
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
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...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy