Promotionspreis 2021

Der Promotionspreis wurde am Science Day, dem 10. November 2021, verliehen. Er geht zu gleichen
Teilen an Frau Dr. Svenja Lehmann für ihre Dissertation mit dem Titel

“Oblique-incidence deposition of ferromagnetic thin films and their
application in magnetoresistive sensors”

Dr. Svenja Lehmann


und an Herrn Dr. Johannes Michel für seine Dissertation mit dem Titel

“Factorization and resummation for precision physics at the LHC”

Dr. Johannes Michel


Svenja Lehmann (nee Willing) was born in Bad Nauheim in 1991. She studied for her bachelor in Physics in Göttingen and then for her master in Nano Sciences in Hamburg. In 2015 she joined DESY Photon Science in the group of Ralf Röhlsberger, working with Kai Schlage on the preparation and characterisation of ultrathin magnetic films under the special condition of oblique incidence deposition (OID). It turned out that these films exhibit unique properties for use in spintronic devices, especially magnetosensors for novel industrial applications.
The aim of the doctoral thesis was to investigate the functional principles of this deposition process for the customized production of novel GMR (giant magnetoresistance) sensors. It was Svenja's task to explore and scientifically investigate the parameter space of this process using a newly developed deposition chamber. In this context, she independently extended this task to the preparation of even more versatile sensors based on the TMR effect (tunneling magnetoresistance). Experts from the sensor industry said that this approach would have very little chance of success due to various fundamental limitations. Eventually, Svenja proved them all wrong.
Her doctoral thesis took place under the special boundary condition of a forefront scientific research work that was embedded in an industrial validation project with an international "big player" from the producing sensor industry (NXP/Eindhoven and Hamburg). This project was laid out in a very close connection between fundamental and applied research, and its success is in greatest parts the result of Svenja’s excellent achievements during her thesis work.
Besides her outstanding scientific work, she displayed a pronounced talent to explain her research activities to students and the interested public in a very clear and original way during numerous events like guided lab tours or public days at DESY.

Johannes Michel born in 1992 near Tübingen. He grew up in Bonn and studied for his bachelor in Münster. He first came to DESY in 2015 as a summer student in the Theory group. Afterwards, he wrote his master thesis jointly at DESY and Münster, and in 2017 he joined the DESY Theory group as a PhD student in the group of Frank Tackmann, working on precision theory predictions for the LHC.
Theoretical predictions for the LHC often receive large corrections from QCD which can severely limit their precision. This limitation can be overcome with the help of so-called factorization theorems, which allow one to break up the full calculation into smaller and more manageable pieces, each of which lives at its own energy scale where it can be calculated precisely. Afterwards, all the different pieces are consistently put back together leading to a final result with much higher precision.
Already during his master thesis, Johannes started to investigate the factorization for new and so far unknown cases, and he continued doing so during his PhD studies. Over the course of three years, he managed to derive and study the factorization for an amazing variety of different, important new cases. One of the highlights was his generalization of a famous, decade-old factorization theorem, making it much more powerful and more widely applicable.
In addition, he also put substantial efforts into explicitly implementing his results, allowing him to obtain some of the most reliable and precise predictions for key LHC processes, e.g. the transverse momentum spectrum of W and Z bosons, as well as making his results available to the experimental community.
After finishing his PhD in the fall of 2020, Johannes moved with his wife and their little daughter to Cambridge in the United States, where he is now working as a postdoctoral researcher at MIT.