Precision measurement of proton asymmetry in neutron decay

This proposal addresses a number of questions, which are at the forefront of particle physics, with main emphasis on the search for new physics beyond the Standard Model (BSM) of particles physics, and in particular, on the question of unification of all forces shortly after the Big Bang. This grand unification is not part of the Standard Model, and new symmetry concepts are needed like left-right symmetry, fundamental fermion compositeness, new particles, leptoquarks, supersymmetry, and many more. In the search for such new symmetries, we see this proposal as a substantial part of the next high-precision frontier in the domain of low-energy studies. The goal of this research project is to measure the proton asymmetry parameter C in polarized neutron beta decay to an unprecedented precision of 0.2%. From such a measurement, we aim for an independent measurement of the ratio of the weak axial-vector to the vector coupling constant, and for improved limits for mass and mixing angle of a WR boson, mediating right-handed interactions, as well as for scalar and tensor interactions from neutron beta decay. The WR boson is associated with the left-right symmetric models. The manifest left-right symmetric models, e.g., are approximately realized with a minimal Higgs sector. Scalar or tensor couplings in turn would occur if yet unknown leptoquarks or charged Higgs bosons were exchanged instead of a W boson. With the PERKEO III experiment, we measure energy spectra and angular correlations of the neutron decay products. PERKEO III was designed to avoid the problems of its preceding experiments PERKEO I and PERKEO II: Its decay volume is considerably larger, which vastly increases the statistical accuracy. And a pulsed neutron beam is used to eliminate leading sources of systematic errors.

Measuring the Laws of Nature There are some numerical values that define the basic properties of our universe. They are just as they are, and no one can tell why. These include, for example, the value of the speed of light, the mass of the electron, or the coupling constants that define 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. With the help of sophisticated neutron experiments, the value of the coupling constant gA has now been determined with an accuracy of 0.04 % From the Big Bang to CERN In many areas of modern physics, it is very important to know the precise value of the coupling constant gA: About one second after the big bang, "primordial nucleosynthesis" began - forming the first elements. The ratio of elements created at that time depends (among other things) on gA. These first few seconds of nucleosynthesis determine the chemical composition of the universe today. Also, the big mystery of the relationship between dark matter and ordinary matter is related to this coupling constant. Last, but not least, it is crucial in order to increase the accuracy of large-scale experiments, such as particle collisions at CERN. The Conundrum of the Decaying Neutron Can dark matter be created when neutrons transform into protons? This is a hotly debated theory but new analyses from this project do not support this idea. Something is amiss in particle physics: two different methods of measuring the lifespan of neutrons yield substantially different results. This mystery has remained unsolved for fifteen years. There has been intense international debate recently regarding a potential explanation: could it be that some neutrons decay into dark matter - invisible particles that have so far been impossible to measure? We have been pursuing this theory. Large quantities of data from high- precision neutron experiments have been re-analysed and additional experiments have been conducted - but no dark matter has been encountered. On the contrary, 95% of the energy field in which the dark matter could theoretically be concealed could be definitively ruled out. There must be other reasons for the discrepancies in the measurements of neutron lifespans. Nevertheless, the data was found to be in excellent agreement with the standard model of particle physics - with no trace of any dark matter. This theory therefore now appears to be rather implausible. And so the search for the mysterious dark matter continues. It has once again been confirmed that precision measurements with neutrons are perfectly suited to the pursuit of fundamental questions in physics.