Marvin Schnubel receives Feodor Lynen Research Fellowship of the Alexander von Humboldt Foundation

New theoretical model to help in the search for new physics

20 July 2023

The theoretical physicist Marvin Schnubel from Johannes Gutenberg University Mainz (JGU) has been awarded a Feodor Lynen Research Fellowship by the Alexander von Humboldt Foundation. It will enable him to conduct research as a postdoc at the famous Brookhaven National Laboratory (BNL) in the USA starting this fall. During his PhD work in the group of Prof. Dr. Matthias Neubert, Marvin Schnubel used a novel theoretical approach to perform precision tests of the Standard Model of particle physics with respect to the Higgs particle. As part of one of his research projects at BNL, he would like to further develop this approach and apply it to other processes.

Marvin Schnubel's "tool of the trade" is the so-called "effective field theory (EFT)". "It is the connecting bracket of all my research projects, in Mainz as well as in Brookhaven," explains Marvin Schnubel. "Because as different as the projects are, the underlying approach is identical and in each case firmly anchored in the field of EFT."

The starting point is the so-called Standard Model (SM) of particle physics. It describes the properties and interactions of the fundamental building blocks - the elementary particles - with astonishing precision. And yet it is clear that it cannot be the final theory. For example, the SM does not explain what dark matter is or why the masses of individual elementary particles vary so greatly. One way to arrive at a more complete theory is to compare theoretical predictions based on the SM with experiment. If there are discrepancies here, it is an indication of new physics. In the context, EFTs represent simplifications of the complete SM that can be used to perform calculations and derive accurate predictions from them.

One of Marvin Schnubel's research projects at BNL is about axion-like particles, which are promising candidates for dark matter - here, their properties, such as their interactions, have to be predicted theoretically and correlated with experimental findings or suitable experiments have to be designed. Corresponding preliminary work from the Mainz period already exists. A second project aims to derive predictions from the Standard Model that are as precise as possible and to compare them with the experimentally measured value. Only if the theory is as precise as the experiment can reliable statements be made regarding possible deviations - and thus the occurrence of new particles. "When particles with very different energies interact, traditional theoretical methods often reach their limits. In my PhD thesis, among others, this problem was solved with respect to the production and decay of the Higgs particle from two gluons at the LHC," says Marvin Schnubel. "For this purpose, we used the so-called Soft Collinear Effective Theory (SCET) on the basis of EFT, with the help of which processes can be decomposed into individual parts and thus the overall process can be better calculated. In doing so, the SCET method is the first to allow sufficiently accurate analytical calculations in the field." At BNL, Marvin Schnubel wants to apply the SCET method to further processes and develop it further in order to establish the method as a state-of-the-art calculation on the one hand and to derive important theoretical predictions for experiments on the other hand.

About the Fellowship

As president of the Alexander von Humboldt Foundation (1975-1979), biochemist and Nobel laureate Feodor Lynen was committed to opening up the international Humboldt Network to young scientists from Germany. With the fellowship named after him and funded by the Federal Ministry of Education and Research, the Humboldt Foundation enables exceptionally qualified postdocs or experienced researchers from Germany who are at the beginning of their academic careers to spend long-term, worldwide research periods abroad.