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 at the ICRC!
The 34th International Cosmic-Ray Conference took place in The Hague, The Netherlands from July 30 to August 6, 2015. More than 800 physicists attended the conference to discuss the latest progress in cosmic-ray and solar physics. Furthermore, recent developments in gamma-ray and neutrino astronomy as well as the hunt for dark matter were covered. The IIHE was clearly represented with 8 posters and 3 talks. Our members presented their results on the Earth WIMP (Weakly Interactive Massive Particles) searches, a possible dark matter candidate, and on multiple analyses that aim to find the sources of neutrinos emission with the IceCube Neutrino Observatory. We focus our attention on: sources with spatial extension in the sky (from 1° to 5°), Gamma-Ray Bursts - extremely energetic explosion possibly associated with the death of a star, Dust Obscured Blazars - a special type of galaxies - and solar flares. The Askaryan Radio Array (ARA) as well as a totally new way to observe high energy neutrinos using radar detection were the subject of two talks! Also, two of our new members presented their previous work on the Cherenkov Telescope Array (CTA) and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The 35th ICRC will take place in Busan, South Korea, where we hope the IIHE will be even better represented!
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.
IIHE IceCube joining in celebration 100 years of Humans on the South Pole
IIHE IceCube joining in celebration 100 years of Humans on 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. Hundred years ago, on the 14th of December 1911, the first human being arrived on the South Pole. Roald Amundsen led the original Norwegian team that arrived, so to celebrate this Norwegian triumph, the Prime Minister of Norway came to the South Pole for 4 days to engage in the festivities.
Pinning down the bottom, charm and top quark
The bottom quark, discovered in 1977, is special, as in LHC collisions it usually lives in unstable particles that travel a few millimeters before they transition into particles that physicists can identify with our very accurate tracking detectors. At the IIHE we are leading the effort in the CMS experiment to identify bottom (or beauty) quarks. Bottom quarks are also extremely useful to identify top quarks, the heaviest known elementary particle, and Brout-Englert-Higgs bosons. At the IIHE we are also developing the tools to distinguish collisions containing bottom quarks from those where charm quarks are produced. This will be extremely useful to study how often top quarks decay to charm quarks instead of b-quarks, a very rare process in the Standard Model that if larger than expected would be a convincing sign for new physics!
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.
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.
South Pole tuning in on "Skyradio"
The Askaryan Radio Array (ARA) is one of the future South Pole neutrino observatories focusing on the detection of neutrinos with energies beyond 10^17 eV. It utilizes radio waves, emitted from neutrino induced cascades in the South Pole ice sheet, to detect neutrino interactions. The detector is currently in the construction phase as is shown in the picture below. A grid of 37 antenna clusters, spaced by 2 km, is planned to be deployed in the South Pole ice at a depth of 200 m. By this, the full ARA detector will cover an instrumented area of about 100 km^2 and represent a state of the art detector for cosmic neutrinos in the energy range between 10^17 eV and 10^19 eV.
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