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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.
First results from a realistic modeling of radio emission by particle cascades in ice
In the previous decade several new experiments (ANITA, NuMoon, ARA, ARIANNA) were proposed to detect high energy (>EeV) neutrino induced particle cascades in dense media such as ice, salt, and moon rock. At the highest energies, these neutrino's are extremely rare and a large detector volume is needed to detect them. Due to the long attenuation length, the detection of the produced radio signals is the most promising tool to search for these rare events. In light of these new experimental efforts, the EVA-code, originally constructed to model radio emission from cosmic-ray-induced air showers, is under development to model radio emission from particle cascades in the South-Pole ice. The ice geometry is included into the code, as well as a parameterized model for the particle cascade. Furthermore, the original EVA-code already incorporated Cherenkov effects in the emission for radio signals moving on curved paths due to a density gradient in the medium. The figure below shows a preliminary result for the electric field as seen by an observer positioned at the ice-air interface. The particle cascade starts at 330 meters depth traveling approximately 10 meters straight upward in the ice until it dies out. The pulses as seen by observers at different lateral distances ranging from 10 m to 300 m are shown. It is seen that the pulse becomes sharper moving outward toward the Cherenkov cone at a lateral distance of approximately 330 meters."
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.
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.
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.
The needle in the haystack
Physicists working in the CMS experiment regularly have to spend their time searching for a needle in a haystack. In other words we look for the rarest of rare collisions that represent very unlikely physics processes. An example of work done at the IIHE is the search for the production of four top quarks (the needle) in the huge dataset recorded by CMS in 2012 (the haystack). Our results put an extremely tight limit on the production of four top quarks, indeed the tightest limit at the LHC so far. As four top quarks are also produced in many new theories of physics such as supersymmetry, this limit can tell us a lot about the validity of these theories.
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.
LHC reaches record energy - first test collisions recorded by CMS experiment
On Thursday 21 May 2015, protons collided in the Large Hadron Collider (LHC) at the record-breaking energy of 13 TeV for the first time. These test collisions were to set up systems that protect the machine and detectors from particles that stray from the edges of the beam. This set-up will give the accelerator team the data they need to ensure that the LHC magnets and detectors are fully protected. The LHC Operations team will continue to monitor beam quality and optimisation of the set-up, while the detectors will use these 'free' testing collisions for calibration and testing. This is an important part of the process that will allow the experimental teams running the detectors ALICE, ATLAS, CMS and LHCb to switch on their experiments fully. Data taking and the start of the LHC's second run is planned for June 2015.
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.
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