Neutrino Programme
Programme Leader
Paul de Jong, Dorothea Samtleben (deputy)
Main points: scientific
ANTARES
- Search for point-sources of neutrinos using astrophysical catalogs and likelihood stacking.
- Constraining the contribution of Gamma-Ray Bursts to the high-energy diffuse neutrino flux.
- Combined search for neutrinos from dark matter self-annihilation in the Galactic Center with ANTARES and IceCube.
- Search for neutrino counterparts of gravitational-wave events detected by LIGO and Virgo during run O2.
- Search for correlations of high-energy neutrinos and ultra-high energy cosmic rays.
- Combined constraints on galactic diffuse neutrino emission and on point sources in the Southern Sky from ANTARES and IceCube.
KM3NeT
- Updated sensitivity estimates for neutrino oscillation parameters, neutrino mass ordering and non-standard neutrino interactions with KM3NeT/ORCA.
- Complete predictions for high-energy neutrino propagation in matter.
- Supernovae real-time trigger (KM3NeT joined SNEWS – Supernova Early Warning System)
- Event reconstruction for KM3NeT using convolutional neural networks.
DUNE
- Analysis of ProtoDUNE test beam data.
- Updated estimates on long-baseline neutrino oscillation physics potential of DUNE.
Main points: technical
KM3NeT
- Deployment of 2 ORCA Detection Units (DUs) and continuous data taking with 6 ORCA DUs.
- Start of phase 2 mass production of Digital Optical Modules and DUs.
- Further improvements in KM3NeT design, sea floor network and optical system.
- Reconstruction and event classification software, general software and oscillation analysis software frameworks.
DUNE
- Publication of the DUNE Technical Design Report (TDR).
- Start of construction of infrastructure for the excavation of the DUNE Far Detector cavities.
Awards/Fellowships
- FuSE (Fundamental Science E-infrastructure): computing infrastructure for LHC, KM3NeT and SKA.
Key positions in collaborations
KM3NeT
- Deputy spokesperson: Aart Heijboer
- Detection Unit integration coordinator: Daan van Eijk
- Optical systems coordinator: Antonio D’Amico
- Mechanics coordinator: Edward Berbee
- Cosmic ray physics group convener: Ronald Bruijn
- Calibration group convener: Dorothea Samtleben
ANTARES
- Point sources group convener: Dorothea Samtleben
Main papers in 2020
ANTARES
- ANTARES and IceCube Combined Search for Neutrino Point-like and Extended Sources in the Southern Sky, The Astrophysical Journal, 892:92 (2020)
KM3NeT
- Dependence of atmospheric muon flux on seawater depth measured with the first KM3NeT detection units, Eur. Phys. J. C 80 (2020) 99.
DUNE
- First results on ProtoDUNE-SP liquid argon time projection chamber performance from a beam test at the CERN Neutrino Platform, J. Instr. 15 (2020) P12004.
Cosmic Rays (Pierre Auger Observatory & GRAND)
Programme Leader
Sijbrand de Jong
Main points: scientific
- Radio Detector Upgrade prototypes performance as expected
- Clear hints of a kink in the ultra-high-energy cosmic ray spectrum pointing at a change of composition and/or source type
Main points: technical
- Installation of ⅔ of the AugerPrime upgrade SSD modules
- GRANDProto300 mechanical and electronics design completed, production started
- Array Auger Radio mechanical and electronics design completed, production imminent
Awards, fellowships, grants, etc.
- Prof. David Nitz was awarded a Radboud Excellence Initiative professorship
- SURFsara Grid resource grant
Key positions in collaborations
- Auger Engineering Radio Array group leader: Jörg Hörandel
- Auger outreach convenor: Charles Timmermans
- Auger Conference Committee chair: Charles Timmermans
- GRAND technical coordinator: Charles Timmermans
Main paper in 2020
- Features of the energy spectrum of cosmic rays above 2.5×1018 eV using the Pierre Auger Observatory, The Pierre Auger Collaboration, Phys. Rev. Lett. 125 (2020) 121106
Dark Matter
Programme Leader
Patrick Decowski
Main points: scientific
- Construction of the XENONnT detector was completed in 2020 and filled with 8.4 tons of liquid xenon. The commissioning of the detector started in the fall of 2020.
- The XENONnT experiment includes several innovative new subsystems, such as a liquid xenon purification system, an online Rn distillation column, a neutron veto system and a triggerless data-acquisition system.
- Meanwhile, XENON1T data analysis is continuing.
- XENON reported an excess of electronic recoil events at energies below ~7 keV. This could indicate a new, ultra-low and hereto not considered background of tritium in the detector or a statistical fluctuation. With more than 180 citations in the literature, more exotic scenarios were also explored by the community.
- A new analysis submitted to PRL lowered the nuclear recoil energy threshold, allowing the search for coherent elastic neutrino-nucleus scattering (CEvNS) of solar B-8 neutrinos with xenon nuclei. Although no events compatible with CEvNS were found, XENON1T reported new limits on low-mass WIMP interactions.
- The Nikhef XAMS R&D xenon-TPC was modified to investigate a single-phase liquid xenon configuration.
- Detailed physics studies for DARWIN, a future forty-ton liquid xenon detector, are ongoing.
- A DARWIN neutrinoless double beta-decay (0n2b) sensitivity study showed that the experiment will have comparable sensitivity to dedicated 0n2b experiments.
- Tina Pollmann joined the University of Amsterdam as an Assistant Professor and is setting up a new R&D lab at Nikhef.
Main points: technical
- Installation of the XENONnT DAQ was completed
Grants
- NWO KLEIN-2 grant “Searching for dark matter in the XENON waste”
- NWA grant “One second after the big bang” for PTOLEMY
Key positions in collaborations
- XENON Editorial Board: Patrick Decowski (chair)
- XENONnT Technical Coordinator: Auke-Pieter Colijn
- DARWIN Executive Board: Patrick Decowski
Main paper in 2020
Excess Electronic Recoil Events in XENON1T, XENON Collaboration, Phys. Rev. D 102, 072004 (2020), arXiv:2006.09721.
Gravitational Waves
Programme Leader & deputy programme leader
Frank Linde & Chris Van Den Broeck
Main scientific points
The analysis of O3a (the first half of the third LIGO-Virgo observing run) delivered another 39 detections, bringing the total to 50. For all of these, Nikhef researchers made significant contributions in terms of detection, tests of the strong-field dynamics of general relativity, as well as other aspects. A number of the new detections had remarkable properties, prompting astrophysicists to rethink some aspects of the formation of neutron stars and black holes:
- GW190425: a presumed binary neutron star merger (though no electromagnetic counterpart was found), with a total mass that exceeds that of any of the binary neutron stars in our galaxy that have been monitored with radio observations.
- GW190521: the most massive binary black hole merger seen so far. For at least one of the two black holes, the mass was such that it could not have been formed directly through the collapse of a star, and most likely it was the result of a previous merger. (The possibility that the masses merely appeared high, due to the GW signal having undergone gravitational lensing, could be excluded thanks to Nikhef efforts.)
- GW190412: a binary black hole signal in which, for the first time, “overtones” to the basic signal could be seen.
- GW190814: here the lighter of the two objects (with 2.6 solar masses) poses a bit of a mystery: it seems too heavy for a neutron star, and too light for a black hole.
Meanwhile, Nikhef researchers are preparing data analysis methodology for a more complete exploitation of the next binary neutron star detections, also in the context of multi-messenger efforts. Notably, PhD student Peter Pang was co-author on a paper published in Science, titled “Multimessenger constraints on the neutron-star equation of state and the Hubble constant” (Nikhef news item: https://www.nikhef.nl/en/news/20168/).
Main other points
In September the Italian Ministry submitted the Einstein Telescope ESFRI application with support from the Netherlands, Belgium, Spain and Poland and with a dual coordinatorship (INFN President/Italy and Nikhef Director/Netherlands). Meanwhile work on the ETpathfinder R&D facility in Maastricht progressed well. The cleanroom contract was awarded and the cleanroom will be ready by March 2021, the tender for the large vacuum vessels was published. Various events (Industry Webinars, Industrial Advisory Boards, Kick-off event) were organized around our Interreg projects ETpathfinder and E-TEST and we submitted a voucher fund (ET2SME) to Interreg-EMR. On the science side, the NWA Dutch Black Hole Consortium (DBHC) application (almost 5 million Euros) was awarded.
Utrecht University, in part thanks to Sectorplan subsidies, launched a new gravitational waves group including Chris Van den Broeck and Sarah Caudill. Andreas Freise and Conor Mow-Lowry joined the VU GW group while Jo van den Brand moved to Maastricht University
Nikhef delivered major parts for the Frequency Dependent Squeezer, one of the largest projects of the ongoing Virgo upgrade.
Key positions in the collaboration
- Sarah Caudill: co-chair of the LIGO-Virgo R&D group on All-sky Searches (2016-2020), and liaison on dark matter to the R&D group on Cosmology.
- Chris Van Den Broeck: co-chair of the LIGO-Virgo R&D group on Tests of General Relativity (2016-2020).
- Matteo Tacca: Virgo commissioning coordinator 2020-2021.
- Alessandro Bertolini: AdV+ project, Filter Cavity subsystem manager since 2018.
- Bas Swinkels: AdV+ project, Electronics, Software and Controls system manager since 2019.
- Sebastian Steinlechner: AdV+ project, Optical System Design subsystem manager since 2020.
- Henk-Jan Bulten: AdV+ project, SBE subsystem manager since 2020.
- Otto Hannuksela (postdoc): founder and head of the LIGO-Virgo group on Gravitational Wave Lensing.
- Anuradha Samajdar (postdoc): coordinator of tests of GW propagation and member of the paper writing team for GW190412.
- Peter Pang (PhD student): coordinator of parameterized tests of GR for the dynamics of binary black hole mergers.
- Andreas Freise: Einstein Telescope Instrumentation Science Board co-chair 2019-2022.
Main papers in 2020
- LIGO Scientific Collaboration and Virgo Collaboration, GWTC-2: Compact Binary Coalescences Observed by LIGO and Virgo During the First Half of the Third Observing Run, arXiv:2010.14527, submitted to Physical Review X
- LIGO Scientific Collaboration and Virgo Collaboration, Tests of General Relativity with Binary Black Holes from the second LIGO-Virgo Gravitational-Wave Transient Catalog, arXiv:2010.14529, accepted by Physical Review D
- S. Sachdev et al. (incl. S. Caudill), An Early-warning System for Electromagnetic Follow-up of Gravitational-wave Events, Astrophys. J. Lett. 905 (2020) L25
- P.T.H. Pang, T. Dietrich, I. Tews, and C. Van Den Broeck, Parameter estimation for strong phase transitions in supranuclear matter using gravitational-wave astronomy, Phys. Rev. Res. 2 (2020) 033514
- T. Dietrich, M.W. Caughlin, P.T.H. Pang, et al., Multimessenger constraints on the neutron-star equation of state and the Hubble constant, Science 370 (2020) 1450-1453