Research Activities

The research in my group is focused on particle physics at hadron colliders. The group participates in the CMS experiment at the Large Hadron Collider (LHC). The LHC is located at CERN, the European Laboratory for Particle Physics, and is currently the largest and most powerful particle accelerator in the world.

My group is involved in CMS data analysis as well as the upgrade of the CMS tracking detectors. We are also applying our expertise in detector systems to medical applications, primarily in radiotherapy.

Selected Publications Public Talks

The CMS Experiment at the CERN LHC

Image based on: 2014 J. Phys.: Conf. Ser. 513 (2014) 022032

CMS Data Analysis

When we analyze CMS data, we focus on processes with Higgs bosons and/or top quarks in the final state.

The discovery of the Higgs boson ten years ago opened up a new window to the universe. We study how strongly the Higgs boson couples to the heaviest known elementary particle, the top quark. We compare the process governed by this process, called ttH, to other processes containing a top quark-antiquark pair (ttZ, ttbb).

We also search for Dark Matter, an elusive form of matter that does not interact with light, assuming that it is produced at the LHC together with a single top quark.

Modern machine-learning techniques such as deep neural networks and graph neural networks are indispensable tools for these analysis projects.

Signal strength for ttH production

Plot from: CMS-HIG-19-011 (July 2024)

CMS Tracking Detectors

In our labs we build fast radiation-hard silicon detectors for the CMS upgrade.

In CMS, silicon tracking detectors are used to measure the momenta of charged particles emerging from proton-proton collisions at the LHC. The large particle flux calls for highly granular, fast, and radiation-hard detectors.

In 2017, the original CMS silicon pixel detector was replaced with a new and improved version. At KIT, we have built around 20% of the modules for the central part of this new detector.

Data-taking at the high-luminosity LHC (HL-LHC) will start in 2029. To exploit the full physics potential of the HL-LHC, the entire CMS silicon tracking system will be replaced. At KIT, we will build around 2000 detector modules for the new silicon strip tracker.

Probe needle over silicon strip sensor

Image credit: F. Wittig

Particle Detectors for Medical Applications

Modern semiconductor tracking detectors promise to take beam monitoring, dosimetry, and secondary particle detection at ion beam therapy centers to the next level.

Monolithic silicon pixel sensors, for example based on HV-CMOS technology, are versatile particle detectors. In collaboration with HIT, the Heidelberg Ion Beam Therapy Center, we evaluate HV-CMOS and other silicon detector technologies for beam monitoring and dosimetry, and for tracking of secondary particles in radiation therapy.

ATLASPix3 secondary-beam telescope at HIT

Illustration from: ETP-KA/2021-20

Publications

Here you find some selected recent publications.

Data Analysis

CMS Collaboration, Measurement of the ttH and tH production rates in the H → bb decay channel with 138 fb-1 of proton-proton collision data at √s = 13 TeV, CMS-HIG-19-011, submitted to JHEP.
CMS Collaboration, Search for dark matter production in association with a single top quark, CMS-PAS-SUS-23-004
CMS Collaboration, Inclusive and differential cross section measurements of ttbb production in the lepton+jets channel at √s = 13 TeV with the CMS detector, JHEP 05 (2024) 042.
CMS Collaboration, Search for ttH production in the H → bb decay channel with leptonic tt decays in proton-proton collisions at √s = 13 TeV with the CMS detector, JHEP 03 (2019) 026, DOI: 10.1007/JHEP03(2019)026.
CMS Collaboration, Observation of ttH production, Phys. Rev. Lett. 120 (2018) no.23, 231801, DOI: 10.1103/PhysRevLett.120.231801.
CMS Collaboration, Sensitivity projections for Higgs boson properties measurements at the HL-LHC, CMS-PAS-FTR-18-011 (2018), https://cds.cern.ch/record/2647699.
U. Husemann, Top-Quark Physics: Status and Prospects, Prog. Part. Nucl. Phys. 95 (2017) 48, DOI: 10.1016/j.ppnp.2017.03.002.
ATLAS Collaboration, Measurement of the top quark pair production cross-section with ATLAS in the single lepton channel, Phys. Lett. B 711 (2012) 244, DOI: 10.1016/j.physletb.2012.03.083.
CDF Collaboration, Search for the Flavor-Changing Neutral-Current Decay t → Zq in ppbar Collisions at √s = 1.96 TeV, Phys. Rev. Lett. 101 (2008) 192002, DOI: 10.1103/PhysRevLett.101.192002.

Machine Learning for Particle Physics

E. Pfeffer et al., A Case Study of Sending Graph Neural Networks Back to the Test Bench for Applications in High-Energy Particle Physics, Computing and Software for Big Science 8 (2024) 13, DOI: 10.1007/s41781-024-00122-3

Particle Detectors

A. Dierlamm et al., A Beam Monitor for Ion Beam Therapy Based on HV-CMOS Pixel Detectors, Instruments 2023, 7(1), 9, DOI: 10.3390/instruments7010009.
CMS Collaboration, The CMS Phase-1 Pixel Detector Upgrade, JINST 16 (2021) no.02, P02027, DOI: 10.1088/1748-0221/16/02/P02027.
CMS Collaboration, The Phase-2 Upgrade of the CMS Tracker, CERN-LHCC-2017-009 (2017), https://cds.cern.ch/record/2272264.
M. Caselle et al., Low-cost bump-bonding processes for high energy physics pixel detectors, JINST 11 (2016) 01, C01050, DOI: 10.1088/1748-0221/11/01/C01050.
CDF Collaboration, Operational Experience, Improvements, and Performance of the CDF Run II Silicon Vertex Detector, Nucl. Instrum. Meth. A 729 (2013) 153, DOI: 10.1016/j.nima.2013.07.015.

As of summer 2024, I have supervised 17 doctoral theses, more than 45 Master theses, and more than 90 Bachelor theses.

Please find my full publication list on INSPIRE.

My ORCID ID: ORCID logo0000-0002-6198-8388

Contact me:

Prof. Ulrich Husemann (he/him/his)
Karlsruhe Institute of Technology (KIT)
Institute of Experimental Particle Physics (ETP)
Hermann-von-Helmholtz-Platz 1
D–76344 Eggenstein-Leopoldshafen
Germany
Campus North office: Building 401, Room 407
Campus South office: Building 30.23, Room 8-19
Phone: +49-721-608-24038
Email: ulrich.husemann@kit.edu
Office hours: Tuesdays, 16:30–17:30
Campus South, 30.23, 8-19 (or by appointment)