Postdoc position in experimental particle physics

Nikhef; Amsterdam; On-site; EUR 41,000 - 64,000; Full time

Job summary

Nikhef ATLAS group at Amsterdam invites applications for a postdoctoral researcher position in experimental particle physics. The role focuses on constructing and executing an ATLAS search for dark-sector bound states using Run 3 data, combining theory and experiment to predict signals and develop robust analysis methods.

You will lead the analysis design, code and documentation, and work closely with Dr Flavia de Almeida Dias at the University of Amsterdam, Nikhef, and collaborators across the

Qualifications

• PhD in experimental high-energy physics or closely related field.
• Experience in collider data analysis and strong software skills (Python, C++, ROOT).
• Ability to develop, document and maintain analysis code in a collaborative research environment; excellent English communication.

Responsibilities

• Lead the design and execution of a new ATLAS search for dark-sector bound states.
• Integrate theory and experiment to develop signal and background models for Run 3 analyses.
• Identify promising unexplored regions of parameter space and optimize the analysis strategy.
• Implement the analysis within the ATLAS Collaboration, contributing to Run 3 publications.
• Collaborate with theory groups and other institutions to maximize scientific impact.

Skills

Python

C++

ROOT

ATLAS experiment

long-lived-particle searches

displaced-vertex reconstruction

triggers

Monte Carlo simulation

statistical inference

dark-sector phenomenology

Education

PhD in experimental high-energy physics

Tools

ROOT

Job description

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 KM3NeT 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 (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.

About the University of Amsterdam
The Faculty of Science has a student body of around 8,000, as well as 1,800 members of staff working in education, research or support services. Researchers and students at the Faculty of Science are fascinated by every aspect of how the world works, be it elementary particles, the birth of the universe or the functioning of the brain.The Institute of Physics (IoP) is located in the centre of the Amsterdam Science Park. The IoP – as part of the Faculty of Science – is housed in a modern building with excellent labs and technical facilities. Surrounded by several national research institutes and with our partners at the Vrije Universiteit Amsterdam, the institute is part of a strong physics centre of international standing. One of the institutes that the IoP has very close ties to is Nikhef, the national institute for subatomic physics in The Netherlands. The present vacancy is fully embedded in the ATLAS group of Nikhef.

The position

Dark matter makes up about a quarter of the Universe, but its fundamental nature remains unknown. It may consist of fundamental particles that interact through new forces in a dark sector. Such forces can give rise to bound states, analogous in some respects to atoms or positronium, involving dark-matter particles, other dark-sector particles, or both. These dark-sector bound states may be produced at the Large Hadron Collider and can yield distinctive signatures, including particles that travel a measurable distance before decaying and, in some scenarios, missing transverse momentum.

We invite applications for a postdoctoral researcher position in experimental particle physics to join the NWO-funded project Reconstructing 25% of the Universe with New LHC Triggers. The project brings together theory and experiment to develop predictions for dark-sector bound states and to perform a dedicated ATLAS search for their asymmetric long-lived-particle signatures in the full Run 3 data set. The search will be designed to probe scenarios in which the bound state contains dark-matter particles, other dark-sector particles, or both.

You will take a leading role in designing and carrying out a new ATLAS search for dark-sector bound states, focusing on asymmetric final states with long-lived particles. This is a timely opportunity: new Run 3 triggers for displaced signatures and the Large-Radius Tracking reconstruction algorithm make it possible to study signal topologies that previous ATLAS searches could not fully access. Your work will connect realistic theoretical predictions with an experimentally robust analysis strategy. You will help identify the most promising unexplored regions of parameter space, develop signal and background models, and implement the analysis in the ATLAS Collaboration. The work is expected to lead to a Run 3 ATLAS publication and to provide methods that can be reused in future long-lived-particle searches.

You will be employed by the University of Amsterdam and work primarily at Nikhef in Amsterdam, embedded in the Nikhef ATLAS group. You will work closely with Dr Flavia de Almeida Dias at the University of Amsterdam and Nikhef, and with Dr Susanne Westhoff at Radboud University. The project also includes a theory PhD researcher based in Nijmegen, creating a close exchange between phenomenology and experimental analysis.

Requirements
We are looking for postdoctoral candidates with an (almost) completed PhD degree in experimental high-energy physics or in a closely related field. The ideal candidate has experience in collider data analysis and strong software skills, preferably including Python, C++ and ROOT. You will be comfortable developing, documenting and maintaining analysis code in a collaborative research environment, and will communicate effectively in spoken and written English. Experience with the ATLAS experiment, long-lived-particle searches, displaced-vertex reconstruction or triggers, Monte Carlo simulation, statistical inference, and/or dark-sector phenomenology would be particularly welcome. The position requires active participation in the ATLAS Collaboration, including periods of work at CERN when needed.

Offer

We offer a temporary employment contract for 38 hours per week for a period of up to 36 months. The preferred starting date is February 2027, but it can be discussed for an earlier or later start.

The gross monthly salary, based on 38 hours per week and dependent on relevant experience, ranges between € 3,706 to € 5,760 (Scale 10). This does not include 8% holiday allowance and 8,3% year-end allowance. The UFO profile Researcher is applicable. A favourable tax agreement, the '30% ruling', may apply to non-Dutch applicants.