The Experimental High Energy Physics (HEP) group at the Niels Bohr Institute has a very long tradition of particle physics studies from the very early days with the important activities in the field photographic emulsion experiments. During the past 30 year or more the group has participated in many different accelerator based experiments, predominantly at CERN. The group has been very successfull in the HERA-B experiment at the HERA at DESY, and the ALEPH experiment at the Large Electron Positron collider (LEP) running from 1989 to 2000. Today the group participates in the ATLAS experiment at the Large Hadron Collider (LHC) at CERN.
The NBI HEP group has long been a part of the ATLAS experiment at the LHC at CERN. The experiment is planned to start in 2008, and take first physics data in the fall 2008.
For the Atlas detector, the group works on the Transition Radiation Tracker (TRT) part of the Inner Detector. We are involved in the design and implementation of the Trigger Timing and Control system, on development of offline software for simulation of the TRT detector, and the TRT testbeam, alignment, and particle identification aspects of the TRT.
The group is also coordinating the hadronic Tau Trigger project, and several members of the group are responsible for the development and commissioning of the final level of the hadronic tau trigger.
The group is very active in several areas of analysis in ATLAS. Our group, including several Ph.D. and master students, are involved in studies of Standard model electro-weak physics, Higgs physics (notably in the tau channel) and several beyond Standard model studies, such as Supersymmetry, New gauge bosons, Extra dimensions and even microscopic Black Holes at ATLAS. The electroweak physics of W and Z bosons will be some of the first physics to be studied at ATLAS, and its understanding is a vital key to the experiment, as all other studies will rely on calibration with these channels. On supersymmetry, we are working on long lived heavy particles and decays to leptons.
We are involved in several projects related to grid computing:nordugrid.org.
GRID.DK grid.dk is a pilot project led by the NBI, with the aim of gauging the feasibility of "gridifying" high performance computing in Danish academia. For information on the project, see grid.dk.
The DAISY project (“Danish AIr Shower arraY”) is a future system of scintillator detector stations at high-schools in the Copenhagen and Åhus regions. Each DAISY station is composed of three plastic scintillator detectors. GPS signals are then used to synchronize signals from the separate detector stations, which will allow for extended cosmic ray air showers and particle flux as a function of time and temperature conditions to be detected and studied. Data and the performance of each DAISY station will be visualized in real time via the internet. The aim of the project is to boost high-school students' interest in science and technology subjects by directly involving them in a modern research project. Therefore students are foreseen to contribute to the, installation, and operation of the detector station situated at their school.
The major contribution of the group to the HERA-B experiment was for the Hera-B Second Level Trigger. The group has been responsible for the construction and daily maintenance of the Second Level Trigger farm and for the track finding algorithms in the Silicon Detector.
ALEPHALEPH detector at the LEP accelerator at CERN. ALEPH played an essential role in the development of the understanding of the Standard Model. The major contribution was the development and deployment of the necessary detector for extremely precise measurements of the luminosity of LEP. Knowledge of the luminosity is one key element in the determination of the number of particle families with light neutrinos. The group also contributed with a Lambda polarization analysis, as well as the single most precise measurement of sin(θW) at LEP using the forward-backward asymmetry in Z→ bb decaysDALI.
At the second stage of the LEP physics program, named LEP2, where the energy was doubled, the group continued the crucial task of luminosity determination but also contributed to the studies of WW events, notably the establishment of the important existence of electro-weak boson self-couplings.