A physical fixed, which is of great importance for basic research, has now be re-measured, with much greater precision than ever before. There are some numerical values that outline the basic properties of our universe. They’re just as they’re and nobody can tell why. These include, for instance, the value of the speed of light, the mass of the electron, or the coupling constants that outline the strength of the forces of nature.
One of these coupling constants, the “weak axial-vector coupling constant” (abbreviated to gA), has now been measured with very high precision. This constant is required to explain nuclear fusion in the sun, to know the formation of parts shortly after the Big Bang, or to know essential experiments in particle physics.
A unique measuring principle referred to as PERKEO was acquired in the 1980s in Heidelberg by Prof. Dirk Dubbers. Hartmut Abele has been committed in the work on the PERKEO detectors for many years, he himself has developed “PERKEO 2” as a part of his thesis. He operates together with his ex-student Prof. Bastian Märkisch from TU Munich and Torsten Soldner from the Institut Laue-Langevin in Grenoble to considerably raise the measurement. With “PERKEO 3,” new computations have now been carried out in Grenoble, far surpassing all previous experiments when it comes to accuracy.
The PEREKO spotter examines neutrons, which decay into protons and emit a neutrino and an electron. “This electron emission isn’t perfectly symmetric,” explains Hartmut Abele. “On one side, just a few more electrons are emitted than on the other—that depends upon the spin direction of the neutron.” The PERKEO detector makes use of strong magnetic fields to gather the electrons in each direction and then counts them. From the power of the asymmetry, i.e., the variation in the number of electrons in the two directions, one can then directly conclude the value of the coupling constant gA.