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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.

Phenomenology

The pheno group — A hint for supersymmetry?

Particle physics phenomenology studies the implications of a theoretical model on experiments in high-energy particle physics and the other way round. From the experimental side, the CMS Collaboration observed in a certain search region 12 events more than expected based on the Standard Model of Particle Physics. Can this be explained by theories that go beyond the Standard Model like supersymmetry? Scientists from the pheno group at the IIHE as well as from the theory group at the ULB collaborated to answer this question. The figure shows how the number of events predicted by a simple supersymmetric model depends on the parameters of the model. The two free parameters, the mass of the stau and the selectron, are shown on the x- and y-axis while the number of events is indicated by the colours. Since we are looking for 12 events coming from new physics, we see from the figure that the model with selectron mass 145 GeV and stau mass 90 GeV can account for the observation of CMS.

IceCube

IceCube results challenge current understanding of Gamma Ray Bursts

Favoured candidates for the emission of Ultra High-Energy Cosmic Rays are Active Galactic Nuclei (AGN) and Gamma Ray Bursts (GRB), both spectacular emitters of high-energy gamma rays arising from particle acceleration in relativistic jets. However, the composition of the particles involved in these processes as well as the acceleration mechanism are very uncertain. The IceCube Neutrino Observatory at the South Pole is honing in on how the most energetic cosmic rays might be produced. IceCube is performing a search for cosmic high-energy neutrinos, which are believed to accompany cosmic ray production, and as such explores the possible sources for cosmic ray production. In a paper published in the 2012 April 19 issue of the journal Nature (Volume 484, Number 7394), the IceCube collaboration describes a search for neutrino emission related to 300 gamma ray bursts observed between May 2008 and April 2010 by the SWIFT and Fermi satellites. Surprisingly, no related neutrino events were found - a result that contradicts 15 years of predictions and challenges most of the leading models for the origin of the highest energy cosmic rays, as shown in the figure.

CMS

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.

IceCube

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.

CMS

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.

CMS

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.

IceCube

Astroparticle Physics revolves around phenomena that involve (astro)physics under the most extreme conditions.

Cosmic explosions, involving black holes with masses a billion times greater than the mass of the Sun, accelerate particles to velocities close to the speed of light and display a variety of relativistic effects. The produced high-energy particles may be detected on Earth and as such can provide us insight in the physical processes underlying these cataclysmic events. Having no electrical charge and interacting only weakly with matter, neutrinos are special astronomical messengers. Only they can carry information from violent cosmological events at the edge of the observable universe directly towards the Earth. 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.

CMS

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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