LPC Distinguished Researcher


Alexander Grohsjean



What I will be working on:

During my time at LPC in 2020, I will finish two complementary searches for dark matter (DM) : a search for top quark associated DM production as well as a search for new scalar particles decaying into a pair of top quarks. Besides exploring so far unconsidered final states, I will pioneer a novel analysis technique which is called attribute learning. A second aspect of my research will be property measurements in the top quark sector. Such measurements do not only allow to probe the SM with highest precision, they also represent powerful searches for new physics. Taking advantage of the current LPC research activities in the field of Higgs and electroweak measurements, I will perform first simultaneous fits to precision CMS data to search for deviations from the Standard Model and to constrain anomalous operators from effective field theories. My research at LPC will also involve close collaboration with Fermilab theory experts. As an example, together with Steve Mrenna, I will work on understanding the benefits of scientific computing for CMS Monte Carlo (MC) simulations.

My role in CMS past and present:

I joined the CMS collaboration by the end of 2014 and I had the pleasure to perform the first measurement of the ttbar cross section at 13 TeV. Together with my research group at DESY, I am currently working on precision differential ttbar cross section and top quark property measurements as well as on searches for dark matter. From 2017 to 2019, I was convener of the top quark properties group and coordinated the interpretation of top quark measurements in terms of effective field theory within CMS and the LHC Top Working Group. Since September 2019, I am Level-2 convener of the CMS MC Group. The group consists of about 100 scientists and PhD students working on the integration of new MC packages into the CMS framework, validation of MC event simulation, and the development of new MC generators. I am also one of the main persons responsible for the CMS MC production which amounts to roughly ~1PByte of simulated data per year. In 2018, my work in the field of CMS MC simulation was recognized with a CMS achievement award. Another key aspect of my research is the phenomenology of particle physics with a special focus on dark matter searches, effective field theory and matrix element methods. In 2016 and 2018, I was organizing the CMS Data Analysis school at DESY.