I am a lecturer at the Faculty of Science, appointed jointly at the astronomical institute Anton Pannekoek (API) and the high-energy physics institute (IHEF). I am a core faculty member of the GRAPPA Research Priority Area. GRAPPA is a centre of excellence of the University of Amsterdam, in which scientists from API, IHEF, and the theoretical physics institute (ITFA) cooperate. The aim of GRAPPA is to bring together theoretical physicists, astronomers and particle physicists, in order to answer some of the most profound questions in Particle Astrophysics and Cosmology: What is the so-called dark matter? How was the universe created? Where do cosmic rays originate? What bounds the smallest particles?

Research

I am working at the interface of astroparticle physics and high-energy particle physics. At the astronomical institute, I am pursuing very-high-energy gamma-ray astronomy with ground-based Imaging Atmospheric Cherenkov telescopes like the currently operating H.E.S.S. array in Namibia or the upcoming Cherenkov Telescope Array (CTA). I am interested in galactic gamma ray sources, particularly the question of the origin of galactic cosmic rays, and in the connection of gamma-ray emission in extragalactic jets to particle acceleration in these jets. I am also actively developing instrumentation for CTA, the future major gamma-ray facility in the very-high-energy regime.

At the high-energy physics institute and Nikhef, I am working on ATLAS at CERN's Large Hadron Collider (LHC). I am particularly active in the areas of dark matter searches in ATLAS and the connection of LHC physics to hadronic physics in cosmic-ray air showers in the atmosphere. In the past I have also been very actively involved in detector operations and commissioning of ATLAS at the LHC, mainly during the LHC startup phase from 2006 to 2011.

• The CTA Observatory

• The H.E.S.S. telescope array

• The ATLAS experiment at the LHC

• The GRAPPA research priority area of the University of Amsterdam

ATLAS Research

I am an ATLAS collaboration member and as such affiliated to Nikhef. In ATLAS at the Large Hadron Collider (LHC), my main science interest is the production of dark matter particles at the LHC.

Weakly Interacting Massive Particles (WIMPs) are one particular kind of new particles that could make up the dark matter of the universe. I am focussing in ATLAS on searches for dark matter pairs produced in assocation with high transverse momentum initial state radiation like a jet. Such mono-jet final states can generically occur in many models of new physics beyond the Standard Model of particle physics.

My second ATLAS research interest is also linked to astroparticle physics - it is the connection of hadronic LHC physics to the physics of air showers. We need to understand the latter well for a whole range of astroparticle physics experiments, like cosmic-ray air shower arrays, ground-based gamma-ray telescopes, or neutrino telescopes. I am working on using LHC data to improve our understanding of the physics of air showers and on optimising the LHC data taking and the analyses pursued in ATLAS for this purpose.

• ATLAS Monojet Dark Matter Search

• Extensive Air Showers and Hadronic Interactions at High Energy

• Forward Measurements at the LHC and the Connection to Cosmic Ray Physics

Master thesis topics

In the areas of ATLAS data analysis and simulations, we are offering up to two master thesis projects per year. Get in touch with us for more details.

H.E.S.S. - The High-Energy Stereoscopic System

H.E.S.S. is an Imaging Atmospheric Cherenkov Telescope (IACT) system situated in Namibia. It is built for pursuing gamma-ray astronomy above gamma-ray energies of 50 GeV, and has been leading this field of very-high-energy gamma-ray astronomy since it started operations in 2003.

The H.E.S.S. Imaging Atmospheric Cherenkov Telescope system in Namibia.

Gamma-ray astronomy explores the sky with photons of energies at least a million times higher than the energy of visible light. As opposed to the photons of visible light, which are mainly emitted by the hot surfaces of stars, photons of gamma-ray energies cannot be produced by thermal processes. There is simply no celestial body hot enough to emit photons of gamma-ray energies. Instead, acceleration processes are believed to be taking place in some of the most violent places of the universe, such as in active galactic nuclei or remnants of star explosions. Charged particles like electrons, positrons, protons or atomic nuclei are believed to be accelerated in such sources to very high energies.

Gamma-ray astronomy is a most valuable tool to make the sites of acceleration visible and to study the physics processes that take place in these sources. On their way to earth charged particles get significantly deflected by the galactic magnetic field, and therefore do not point back to their production origin. Instead, neutral gamma-rays, produced in interactions of the accelerated particles with magnetic fields, photons, or intergalactic gas, travel on a straight path to earth. Therefore, their direction of origin points back to where they got produced, which is often close to the accelerators of the charged particles.

H.E.S.S. gamma-ray image of the supernova remnant RXJ1713.

I am working on measuring gamma-ray emission from supernova remnants, the prime source candidates for high-energy cosmic rays in our galaxy. I am furthermore interested in measuring diffuse gamma-ray emission over angular scales of more than 2 degrees with H.E.S.S., which is particularly difficult because of the dominant background from diffuse charged cosmic rays faking gamma rays. Finally, related to my CTA precision pointing activities, I am interested in H.E.S.S. measurements of radio galaxies like M87 or Centaurus A, and the science question of where particles are accelerated in these objects (the jets, the black hole, ...).

We are also involved in the H.E.S.S. camera electronics upgrade, and will test electronics components for this upgrade (scheduled for 2015 to 2016) in Amsterdam.

• Background information: Review of TeV Gamma-Ray Astronomy

• Background information: H.E.S.S. Measurement of Diffuse Gamma-Ray Emission

• Background information: Gamma-Ray Emission close to Supermassive Black Holes

CTA - The Cherenkov Telescope Array

Areas of activity of my group in CTA:

• Establishing an important Dutch contribution to CTA
• Hardware R&D for CTA, focussing on the areas of fast readout electronics, high-precision time synchronisation between telescopes separated by 100's of metres, high-precision positioning of CTA telescope
•  We are particularly focussing on the Small Size Telescopes (SSTs) of CTA. These small telescopes are the most numerous telescope class of CTA, spread out over a large area to measure gamma rays of the highest energies (300 TeV).

• CHEC - A Camera Prototype for the SSTs of CTA

• The CTA Science Case (journal homepage, special journal issue on CTA)

Master thesis topics

We are offering master thesis projects in the areas of H.E.S.S. data analysis, CTA simulations, and hardware R&D work. If  you are interested, get in touch with us.

Education

Employment

Fellowships, Awards, Grants

Supervision (9 PhD students and postdocs supervised)

Teaching

Organisation of Scientific Meetings (6 events co-chaired or major organisational contributions)

Leadership, Coordination, Responsibilities, Scientific Work 

• Scientific journal referee for Astroparticle Physics, Monthly Notices of the Royal Astronomical Society, Astronomy & Astrophysics

• Editorial board chair in ATLAS (internal review board, one such board per on-going analysis)

• Since 2013 Member of 3 Ph.D. evaluation committees, Grebe (U Nijmegen), Fraenkel (U Groningen), Bogazzi (U Leiden)

Membership in experimental consortia

Publications

The ten most important journal publications with significant personal contributions are listed. Ten more such journal publications with personal contributions are not listed.

• Mono-everything: combined limits on dark matter production at colliders from multiple final states, N. Zhou, D. Berge, D. Whiteson, Phys. Rev. D 87 (2013) 095013, arXiv:hep-ex/1302.3619.

• Search for dark matter candidates and large extra dimensions in events with a jet and missing transverse momentum with the ATLAS detector, The ATLAS Collaboration, JHEP 1304 (2013) 075, arXiv:hep-ex/1210.4491. 
• Performance of the ATLAS Trigger System in 2010, The ATLAS Collaboration, CERN-PH-EP-2011-078, EPJC 72 (2012) 1849, arXiv:hep-ex/1110.1530.
• Luminosity Determination in pp Collisions at √s=7 TeV Using the ATLAS Detector at the LHC, The ATLAS Collaboration, EPJC 71 (2011) 1630, arXiv:hep-ex/1101.2185.
• Background modeling in very-high-energy gamma-ray astronomy, D. Berge, S. Funk, J. Hinton, Astron. Astrophys. 466 (2007) 1219-1229, arXiv:astro-ph/0610959v1.

• Primary particle acceleration above 100 TeV in the shell-type supernova remnant RX J1713.7—3946 with deep H.E.S.S. observations, The H.E.S.S. collaboration, Astron. Astrophys. 464 (2007) 235-243, arXiv:astro-ph/0611813. 
• Discovery of very-high-energy gamma-rays from the Galactic Centre ridge, The H.E.S.S. collaboration, Nature 439 (2006) 695-698, arXiv:astro-ph/0603021.

• A detailed spectral and morphological study of the gamma-ray supernova remnant RX J1713.7—3946 with H.E.S.S., The H.E.S.S. collaboration, Astron. Astrophys. 449 (2006) 223-242, arXiv:astro-ph/0511678.  
• The H.E.S.S. Survey of the Inner Galaxy In Very High Energy Gamma Rays, The H.E.S.S. collaboration, Astrophys. J. 636 (2006) 777-797, arXiv:astro-ph/0510397.
• High energy particle acceleration in the shell of a supernova remnant, The H.E.S.S. collaboration, Nature 432 (2004) 75-77, arXiv:astro-ph/0411533.

Invited Presentations to International Conferences and Workshops

Invited colloquium talks (15 since 2005) at universities and research institutes are not listed below.

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