PRACE help researchers calculate mass difference between neutrons and protons


With the help of PRACE HPC resources, a team of physicists from France, Germany, and Hungary headed by Zoltán Fodor, a researcher from Wuppertal, has successfully calculated the tiny neutron-proton mass difference. The results of this research, published in the 27 March 2015 edition of Science, are considered a milestone by many physicists and confirm the theory of the strong interaction.

The fact that the neutron is slightly more massive than the proton is what gives atomic nuclei the properties affecting the existence and stability of atoms – the foundation of our world. Eighty years after the discovery of the neutron, Zoltán Fodor’s team successfully calculated the tiny neutron-proton mass difference. The team was made of physicists from France, Germany, and Hungary. Fodor is a researcher at University of Wuppertal, Jülich Supercomputing Centre, and Eötvös University.

To carry out the necessary calculations, the team developed a new class of simulation techniques combining the laws of quantum chromodynamics with those of quantum electrodynamics in order to precisely determine the effects of electromagnetic interactions.

According to Professor Kurt Binder, Chairman of the Scientific Council of the John von Neumann Institute for Computing (NIC) and member of the German Gauss Centre for Supercomputing, “Only using world-class computers, such as those available to the science community at Forschungszentrum Jülich, was it possible to achieve this milestone in computer simulation.” Computation time on JUQUEEN to is allocated to users via the PRACE Calls for Proposals. The hours on JUQUEEN were complemented in the process by national resources provided by CNRS and GENCI in France, as well as GCS in Germany at the computing centres of Garching (LRZ) and Stuttgart (HLRS).

“Forschungszentrum Jülich is supporting the work of excellent researchers in many areas of science with its supercomputers. Basic research such as elementary particle physics is an area where methods are forged, and the resulting tools are also welcomed by several other users,” says Prof. Dr. Sebastian M. Schmidt, member of the Board of Directors at Jülich who has supported and encouraged these scientific activities for years.

Some of the results of Fodor’s research were recently published in Science (Journal reference: Science 347:1452-1455,2015 – see This publication is considered a world-premiere in fundamental physics.

Project details

His project entitled “QCDpQED – QCD plus QED and the stability of matter” received 91 million core hours on JUQUEEN @ GCS@FZJ, Germany through the PRACE 6th Call for Proposals for Project Access.

Further work

  • Zoltán Fodor spoke at the DEISA PRACE Symposium (11-13 May 2009) on “QCD Breakthrough 2008”
  • He received 63 million core hours on JUGENE @ GCS@FZJ, Germany via the PRACE Early Access Call for his project entitled “QCD Thermodynamics with 2+1+1 improved dynamical flavors”.
  • He collaborated in the project entitled “FREEZEOUT – Heavy ion phenomenology from lattice simulations” led by Szabolcs Borsanyi of the Bergische Universität Wuppertalm, Germany, That project received 18 million core hour on JUQUEEN @ GCS@FZJ, Germany and 73.2 million core hour on FERMI @ CINECA, Italy, under the 8th Call for Proposals for PRACE Project Access.


The quotes in this article are republished from the article that appeared in supercomputing online on Thursday, 26 March 2015:

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