After the discovery of the Higgs boson in 2012, one of the crucial future challenges for the LHC is to probe its most enigmatic property, the Higgs potential, which can manifest itself in LHC collisions through the production of Higgs boson pairs. These decays, which are 1000 times more rare than single Higgs production according to the Standard Model have not yet been observed. Observation of two-Higgs production is one the most important milestone for the LHC physics program, and will help constrain our knowledge of the Higgs potential, which has shaped the universe at its time of creation, and may hold strong clues about the existence of new physics beyond the Standard Model. 
Position 1 will focus on the search for the extremely rare process of ttHH production in LHC Run-3 data. This search will include all tt final states, and will include boosted final states. The analysis strategy is strongly focused on advanced machine learning techniques, developing attention-based transformer models that will directly classify events from the low-level data, rather than high-level objects, and which may ultimately include higher-level tasks such as Higgs boson mass regression for the analyzed data. The boosted object analysis will have a strong synergy with boosted analyses we are performing in other two-Higgs channels. This position is co-supervised by prof. dr. Ivo van Vulpen, dr. Clara Nellist, and dr. Sascha Caron. The candidates is employed by the University of Amsterdam, is primarily based at Nikhef in Amsterdam.

Position 2 will focus on the reconstruction of  two-Higgs decay channel into a pair of photons and a pair of b-quarks (HHàbbγγ) , which currently provides the tightest constraints, and on the combined interpretation of all reconstructed diHiggs channels. Apart from the Run-3 diHiggs combination of all channels, which will provide the ultimate statement on diHiggs production that can be obtained with the LHC Run-3 data, a combination of single-Higgs, di-Higgs and triple-Higgs production measurements will allow to constrain the trilinear and quartic Higgs coupling, and thus the shape of the Higgs potential with unprecedented precision. In this position you will closely work together with PhD students involved in the main diHiggs channels (bbbb, bbττ and bbVV) for the combined interpretation and with a postdoc that is being recruited simultaneously that work on novel ML-based strategies to improve the precision of diHiggs combined interpretations. This position is co-supervised by prof. dr. Wouter Verkerke, prof. dr. Tristan du Pree. The candidates is employed by the University of Amsterdam, is primarily based at Nikhef in Amsterdam.

The positions offered here are part of a NWO-funded physics program 'The potential of the Higgs boson', with prof. dr. Pamela Ferrari as principle investigator, which will ultimately comprise 7 PhD positions and 2 postdoc positions in the Nikhef ATLAS group in the period 2025-2030 all focused on the Higgs boson potential, complemented by 9 Nikhef staff scientists that offer supervision, networking opportunities and a specialized training program in data analysis techniques and Higgs boson physics.

We are looking for PhD candidates with an (almost) completed Master degree in high-energy physics or in a closely related field. The ideal candidate has a strong interest in data analysis, has good software skills (Python, C++, ROOT) and has (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. 

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