IIHE - Interuniversity Institute for High Energies (ULB-VUB)The IIHE was created in 1972 at the initiative of the academic authorities of both the Université Libre de Bruxelles and Vrije Universiteit Brussel.
Its main topic of research is the physics of elementary particles.
The present research programme is based on the extensive use of the high energy particle accelerators and experimental facilities at CERN (Switzerland) and DESY (Germany) as well as on non-accelerator experiments at the South Pole.
The main goal of this experiments is the study of the strong, electromagnetic and weak interactions of the most elementary building blocks of matter. All these experiments are performed in the framework of large international collaborations and have led to important R&D activities and/or applications concerning particle detectors and computing and networking systems.
Research at the IIHE is mainly funded by Belgian national and regional agencies, in particular the Fonds National de la Recherche Scientifique (FNRS) en het Fonds voor Wetenschappelijk Onderzoek (FWO) and by both universities through their Research Councils.
The IIHE includes 19 members of the permanent scientific staff, 20 postdocs and guests, 31 doctoral students, 8 masters students, and 15 engineering, computing and administrative professionals.
Here you see an event recorded by IceCube in January 2008, when the detector was still in construction!
At that time, 22 strings were already taking data and 18 other strings were freshly deployed. Every colored bubble indicates the detection of one or more Cerenkov photons created by the cross of a charged particle by one of the sensors deployed in the ice. The size of the circles reflects the intensity of the signal. The color indicates the arrival time from red (early) to blue (late). These informations combined with the geometry of the detector allow first guess reconstructions of the initial track.
Dark matter searches with IceCube
According to the most recent observations and based on the standard model of cosmology, dark matter makes up 26.8% of the energy density in our Universe The argument that yet to be detected Weakly Interacting Massive Particles (WIMPs) make up the dark matter is compelling. Over time, WIMPs may accumulate in the center of the Sun and Earth, and annihilate with each other. The decay products may vary, and most of them will interact and decay in the massive body. If neutrinos are created from those secondaries, they will escape and provide a neutrino ﬂux. This neutrino flux could be measured by the IceCube Neutrino Detector. Data taken by AMANDA and IceCube have been analysed at the IIHE to search for WIMPs in the centre of the Sun and Earth; no significant excess above background was observed so far.
Here you see the installation of the the Compact Muon Solenoid forward tracker,
which was partly built at the IIHE. The IIHE contributed to the construction of the over 200 square meter silicon tracker, the most ambitious particle tracking detector every built. Contributions were made to the assembly of detectors and their support structures, and the assembly of the detectors on a wheel such as you can see here. The tracker was installed inside the Compact Muon Solenoid detector in December 2007.
Shown here is a result of the 2010 LHC run at the Compact Muon Solenoid,
studying the invariant mass of electron pairs produced at the Large Hadron Collider. Shown is the data, as black dots, and the simulation predicting what we should expect according to the particle physics Standard Model (colored bands). The IIHE is actively involved in the study of this kind of collisions, in collaboration with other groups of the CMS experiment. An example of what a signature due to a new particle would look like is the (simulated) gray bump. When more data is collected in 2011 we will have enough information to also study the right side of the plot and look if there are any such particles produced at the LHC. If the grey distribution would be observed, it would be a hint of the existence of, for example, extra dimensions.
IIHE collaborators at the CMS detector at CERN
CMS is one of the two general purpose detectors for the proton-proton collider of CERN, the LHC. CMS is an international collaboration in which Belgium and in particular the IIHE has an important participation. The Brussels group has participated in the contruction of the endcap tracker detector of CMS. The Brussels teams were involved in the study of the CMS physics potential using simulations, and are now analysing the fresh LHC data at the energy of 7 TeV in the proton-proton centre of mass.
IceCube observes first hint of astrophysical high-energy neutrinos
Two neutrino candidate events detected at the IceCube Neutrino Observatory, dubbed "Bert and Ernie", are the two highest energy neutrinos ever observed so far, with an estimated deposited energy of about 1 PeV. The IceCube event displays of these two events are shown in the figures below, where for comparison one should realize that a single event covers an area comparable with the Maracana football stadium in Rio de Janeiro! The probability that these two events are not background, i.e. anything else in the detector besides astrophysical neutrinos, is at the 2.8 sigma level and does not allow claiming a first observation of astrophysical neutrinos. Further details may be found in Physical Review Letters 111 (2013) 081801. To improve the detection sensitivity, a follow-up search on the same data period has been conducted. The new analysis selects high-energy neutrino events with vertices well contained in the detector volume and exploits veto algorithms by using the outer layers of IceCube sensors. By means of this new analysis method 26 new events have been detected. The entire sample of 28 events has properties consistent in flavour, arrival direction and energy with generic expectations for neutrinos of extraterrestrial origin.
The IceCube neutrino observatory at the South Pole is the world's largest neutrino telescope, completed in 2011 and taking data since 2005!
The detector is composed of 80 strings of 60 sensors deployed in the Antarctic glacier, between 1500 and 2500 m of depth. As its name suggests, IceCube covers an instrumented volume of one cubic kilometer. The DeepCore extension of IceCube is composed of 6 additional string in the center of the IceCube array, where the puriest ice can be found. At the surface, the IceTop air shower array equiped each IceCube string with 2 pairs of sensors in an ice tank of 3 square-meter.
IIHE students at the South Pole
In the Antarctic Summer 2011-2012, two PhD Student from the IIHE were working at the Pole. Thomas Meures, who went down for the ARA experiment and David Heereman, working for the IceCube Observatory. Both projects are looking for Neutrinos via their interactions in the Ice. At the Inter-university Institute for High Energies (IIHE) in Brussels we are involved in a world wide effort to search for high-energy neutrinos originating from cosmic phenomena. For this we use the world's largest neutrino telescope, located at the South Pole.