Two PhD ATLAS group

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. Nikhef is a partnership between six major Dutch universities and NWO-I Foundation, the Institutes Organization of the Dutch Research Council (NWO).

Among the research collaborations Nikhef participates in are the ALICE, ATLAS and LHCb experiments at CERN, the KM3

NeT neutrino telescope in the Mediterranean, the Virgo gravitational waves interferometer in Pisa, the Xenon-nT dark matter experiment in Gran Sasso, the Pierre Auger cosmic ray observatory in Argentina, and the eEDM research programme in Groningen. There are also scientific groups on Theory, Physics Data Processing and Detector R&D. Nikhef avails over excellently equipped technical departments in mechanics, electronics and computing.

The Nikhef ATLAS 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 ), 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 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. Candidates will be employed by the University of Amsterdam, and will be based at Nikhef in Amsterdam.

Requirements
We are looking for PhD candidates with an (almost) completed…