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 process 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.

Position 1 will focus on Higgs boson production through the ggàHZ 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 of today no separate measurement of its cross section is available due to the large background of the qqàHZ process. The use, and further development, of modern techniques such as Transformer networks open a window to exploring this process.

Position 2 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 gg->HZ and rare top-quark processes, including the tZq process, and then gradually extended to other process. 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.

We are looking for PhD candidates with:

• 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 allowance and 8,3% year-end allowance. The UFO profile PhD candidate is applicable. A favourable tax agreement, the ‘30% ruling’, may apply to non-Dutch applicants. The preferred starting date is to be discussed. This employment should lead to a dissertation (PhD thesis). We will draft an educational plan that includes attendance of courses and (international) meetings. We also expect you to assist in teaching undergraduates and master students. During the doctoral program there is the possibility for extended stays at CERN, up to a total of 1 year. Candidates will be employed by the University of Amsterdam, and will be based at Nikhef in Amsterdam. Further details can be found here.

The Collective Labour Agreement of Universities of the Netherlands is applicable.