Two PhD ATLAS Group

Deadline 8 Mar ’26 Published 9 Feb ’26 Vacancy

Nikhef is the national institute for subatomic physics in the Netherlands. At Nikhef, approximately 220 physicists and 80 technical staff work together in an open and international scientific environment. Together they perform theoretical and experimental research in the fields of particle and astroparticle physics. Your research is part of the ATLAS Research Group.

The Nikhef ATLAS group consists of a total of 15 scientific staff, typically 5 postdocs and 15 PhD students. As a founding member of the ATLAS collaboration, the group has a long-term involvement in detector construction (the semiconductor tracker, barrel muon chambers, readout, alignment, and data acquisition). For the phase‑2 upgrade (2027‑2030), we will instrument and commission one of the end‑caps of a new all‑silicon inner tracking system (ITk) in Amsterdam, commission the High Granularity Timing Detector (HGTD), and develop the new universal readout system (FELIX) for ATLAS detector systems.

The group also has a strong record in track reconstruction, flavour tagging algorithm development as well as physics data analysis, with a focus on Higgs boson physics, top quark physics, and searches for new physics signatures.

After the discovery of the Higgs boson in 2012 at the LHC, the hunt for physics beyond the Standard Model (SM) has intensified. A wide range of possible new physics scenarios at high energy scales can be described by the theoretical framework SM Effective Field Theory (SM‑EFT) at energy scales below where new interactions could be directly observed, and which are currently accessible by the LHC.

Subtle effects at LHC energy scales may be expected in processes that involve the two most massive particles of the SM, the top quark and Higgs boson. The top‑Higgs interaction is currently poorly constrained, but new deep learning techniques that exploit the structure of the Lagrangian provide a tantalizing chance to probe anomalous couplings with unprecedented precision. In SM Effective Field Theory anomalous top‑Higgs interactions are expressed in the operator Oφt, which remains one of the most poorly constrained operators of SM‑EFT to date.

This position will focus on Higgs boson production through the g‑g → HZ process, where the top quark contributes via a quantum loop and is therefore sensitive to top‑Higgs interactions. This process is interesting by itself as, to date, no separate measurement of its cross section is available due to the large background of the q q → HZ process. The use, and further development, of modern techniques such as Transformer networks open a window to exploring this process.

This position will focus on new experimental results to extract poorly constrained SMEFT coefficients of the corresponding operators, including Oφt, which models anomalous top‑Higgs interactions. Understanding systematic effects and their propagation in deep learning networks is crucial for this project. The playground for this study is initially provided by the g → HZ and rare top‑quark processes, including the tZq process, and then gradually extended to other processes.

Both positions are jointly supervised by Prof. dr. Marcel Vreeswijk and Prof. dr. Wouter Verkerke. The positions offered here are funded by the NWO‑M2‑project “When Higgs bosons meet Top quarks” and embedded in the Nikhef ATLAS group.

• an (almost) completed Master degree in high‑energy physics or in a closely related field;
• a strong interest in data analysis;
• good software skills (Python, C++, ROOT);
• (some) research experience in experimental particle physics.

Experience with machine learning algorithms and software is desirable but not required.

We offer a temporary contract for 38 hours per week for the duration of 4 years (the initial contract will be for a period of 18 months and after satisfactory evaluation it will be extended for a total duration of 4 years). The gross monthly salary, based on 38 hours per week ranges between € 3,059 to € 3,881 (Scale P). This does not include 8 % holiday…