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.
IIHE students at the South Pole
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 IceCube neutrino observatory at the South Pole, the world's largest neutrino telescope which is now completed and taking data.Here you see a really cool phenomenon made by ice crystals that are drifting in the air at low levels and acting as prisms for the light rays passing through them. In this way, a halo around the sun is visible. In this picture, IIHE PhD Student David put his head in front of the sun and the halo becomes visible more easily.
Candidate top quark +W boson collision event at CERN
Shown is a candidate collision event from the 2010 LHC run that was selected in the search for one top quark associated with a W boson at the Compact Muon Solenoid experiment at CERN. IIHE scientists are leading the analysis effort in the detailed study of these kind of collisions. Understanding single top production is relevant both for the detailed understanding of the physics of top quark production but also in the context of the Standard Model Quantum Chromodynamics in general as this process is special because of the production of a single heavy quark in association with a gauge boson. This event topology is very similar to that expected for new physics or the elusive Higgs boson, for which this kind of events are a background.
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.
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.
IIHE students at the South Pole
Falling off the earth is a serious risk at the South Pole. Down there, at the very end of the world, everything is different.. 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 IceCube neutrino observatory at the South Pole, the world's largest neutrino telescope which is now completed and taking data.
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.
Observation of a New Particle with a Mass of 125 GeV
In a joint seminarar at CERN and the “ICHEP 2012” conference in Melbourne, researchers of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) presented their preliminary results on the search for the standard model (SM) Brout-Englert-Higgs boson in their data recorded up to June 2012. CMS observes an excess of events at a mass of approximately 125 GeV with a statistical significance of five standard deviations (5 sigma) above background expectations. The probability of the background alone fluctuating up by this amount or more is about one in three million. The evidence is strongest in the two final states with the best mass resolution: first the two-photon final state and second the final state with two pairs of charged leptons (electrons or muons). We interpret this to be due to the production of a previously unobserved particle with a mass of around 125 GeV.
The Compact Muon Solenoid forward tracker was partly built at the IIHE.
Here you see the assembly of several of the (black) support structures on which the tracker detectors were mounted. The IIHE contributed to the construction of the over 200 square meter silicon tracker, the most ambitious particle tracking detector ever built. Other contributions were made to the assembly of detector modules and the installation on the detector. Each detector element can identify the path of charged particles to a precision of up to 1/100 millimeters.
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