T he Norwegian atlas project Status report August 31st 2000

The physics potential at ATLAS and the LHC

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The physics potential at ATLAS and the LHC.

Future progress in the field of elementary particle physics are related to three major questions with special relevance for LHC :

  • What is the source and mechanism of electroweak symmetry breaking in the Standard Model (SM)? This question can be addressed by searches for Higgs-bosons or equivalent effects.

  • Can we unify the forces of nature further and find a naturally consistent theory of matter which works all the way to the unification or Planck scale ? This can experimentally be addressed in the framework of supersymmetric models, which are particularly attractive because these models can stabilise the gauge couplings. The SM symmetry breaking appears naturally in the models. String theories have been known to be able to incorporate gravity in a unified model. Recent developments gives hope for finding experimental signatures for such theories at the LHC, should the models be correct.

  • Finally it is important to check the consistency of the Standard Model through precision measurements of its parameters, as any inconsistency is a sign of new physics beyond the Staldard Model. The precision of W boson and top quark masses and couplings should be greatly improved through measurements at the LHC. Furthermore, detailed studies of B-quark systems will give much insight into the CP-violating parameters of the Standard Model, a sector where precision measurements still are scarce.

ATLAS is conceived as a general purpose instrument which should be able to exploit the full physics potential of the LHC.
1.2 The Norwegian ATLAS MoU deliverables and background information.

The work of the various groups and national responsibilities for detector component delivery are defined in the ATLAS Memorandum of Understanding (MoU). The MoU was signed in June 1998 by Norway on the basis of an agreement about the eight year project described in this status report. The Norwegian ATLAS project has three main components:

  1. Development, purchase and testing of silicon detectors for the ATLAS SCT. This is the most costly component. The Norwegian groups shall provide about 2000 silicon strip detectors sufficient for the innermost of the four barrel cylinders (145 cm long and radius equal 30 cm) of the ATLAS SCT. The detectors are developed for operation in a high radiation environment at bias voltages of up to 350V. The silicon detectors are discussed further in chapter 2.

  2. Construction of 480 modules for the ATLAS SCT, corresponding to all modules on the innermost barrel cylinder. This is a collaboration between the particle physics groups in Bergen, Oslo and Uppsala with sharing of the workload as described in section 1.3. This is the most demanding task in the coming years in terms of competence, workload, manpower and infrastructure. See chapter 3 for details.

  3. The ATLAS Common Fund contribution. Most of this contribution will be the delivery of Liquid Argon and Nitrogen tanks by SB-verksted (Industrial manufacturer of mechanical constructions) in the city of Drammen. The tanks are designed in collaboration with the Norwegian University of Science and Technology, Trondheim. The tanks are part of the cryogenics system for the ATLAS Liquid Argon Calorimeters. In terms of cost this is second largest Norwegian contribution. The Common Fund activities are discussed in chapter 4.

In addition the Norwegian groups are involved in the cooling of the ATLAS ID (an evaporative cooling system) This is important because the development and production costs for the cooling system have been substantially underestimated. University of Oslo collaborates with Gjøvik College who has an important role in this work, related to development of software for the Detector Control System (DCS) which is being used for control and measurements of the SCT cooling systems. At the Univ. of Oslo two of the students working in this area are students at the Institute for Informatics. Finally, in collaboration with the “Norwegian Physics Analysis Project”, ATLAS relevant software development and physics studies are performed (see chapter 5).

The Norwegian groups involved in ATLAS are UiB (University of Bergen), UiO (University of Oslo), NTNU (The Norwegian University of Science and Technology, Trondheim), and HiG (Gjøvik College).The background for the two major Norwegian ATLAS contributions are the long lasting collaboration with SINTEF (a Norwegian industrial research institute) within silicon detectors, ASICs, cooling and packaging for the DELPHI and RD20 collaborations.; and the work of the NTNU within the CERN cryogenics groups and their contact to SB-verksted in Drammen. A branch of SINTEF, situated in Trondheim, collaborates with NTNU on the cryogenic work.
1.3 Worksharing Bergen, Oslo, Uppsala, Trondheim, Gjøvik - infrastructure.

The Bergen, Oslo and Uppsala groups are responsible for construction of 6m2 of silicon modules (480 modules) for ATLAS to be placed in the innermost cylinder in the barrel region. These should be delivered fully tested for final installation on a carbon fibre structure. In more detail :

  • Norway is responsible for delivery and testing of all sensors on this cylinder, plus one-third of the cooling system of the ATLAS silicon-systems, plus various minor components (cables, connectors and small contributions to the readout ASIC and optical links).

  • Uppsala is responsible for delivery of hybrids and most of the radiation hard readout electronics plus various smaller items on a similar scale as the Norwegian groups.

The preparation for construction of the silicon detector system for ATLAS started in 1992. It was a natural development of the expertise and know-how built up for the DELPHI-experiment within silicon detector systems with integrated readout. The workload for the module construction is shared as follow (this sharing was defined in a series of discussion in 1996 and comprises definition of tasks, equipment and manpower) :

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