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Participation in ATLAS at LHC

The ATLAS collaboration unites about 1700 physicists and engineers from 150 scientific organizations of 33 countries. It develops, produces and will exploit the ATLAS detector. The main goal of the ATLAS detector is to discover and study the Higgs Boson, the particle explaining the mass origin of quarks and leptons. At the same time the broad spectrum of actual problems of modern high energy physics will be explored with its help. Among them are: processes of creation and decay of the top-quark, physics of B-mesons, testing of supersymmetric theory predictions, search for phenomena beyond the Standard Model. Experimental data (processes of creation of secondary particles in proton-proton interactions at 14 TeV energy) will be acquired in frontal collisions of proton beams, accelerated in the ring of the Large Hadron Collider (LHC), which is being built now in the European Laboratory of Nuclear Research (CERN, Geneva).

NC PHEP joined the ATLAS collaboration in 1998. NC PHEP ATLAS-group in close collaboration with colleagues from the Joint Institute of Nuclear Research (JINR, Dubna) participates in development and production of three subsystems of the Atlas detector: hadron calorimeter (Tile-Calorimeter), electromagnetic liquid argon calorimeter (LAr-calorimeter) and muon spectrometer.

The first contribution to the Atlas project was production of the set of so called intermediate plates, the constituent element of the Tile-Calorimeter autonomic module design. The set includes 244800 plates of 12 dimension-types. Sheets of cold-rolled steel Fe-360 with 4.05 mm thickness and 400x1620 mm2 dimensions were used as blanks. Typical tolerance requirements were 0.1 mm. Mass-production (by punching) was performed by the Minsk Tractor Plant. The total volume of the metal processed was about 320 tons. The Atlas-group has organized and performed delivery of fabricated goods to Dubna and Protvino (Russia), Prague (Czechia) and Pisa (Italy).

In 1999-2000 the mentioned group provided transportation of 21-ton autonomic modules of Tile-Calorimeter, assembled in JINR, on the route Dubna-Geneva.

In collaboration with colleagues from Scientific Research Department of the Belarus State University the fixture set for assembly work-bench for Muon Spectrometer wire chambers was produced and delivered to JINR. The set consists of 1440 cylinders of three dimension-types with complex profile configuration. The distinctive feature of that job was the high requirement to dimension tolerances, 5 mm.

In collaboration with colleagues from JINR, Scientific Research Department of the Belarus State University and designers of Minsk Machine-Tool Plant of October Revolution (MZOR) the draft project of certification system for wire chambers of Muon Spectrometer (mobile manipulator and work-bench) was designed. Manipulator serves for chamber transportation (its dimensions are 3200x2160x500 mm3, the weight is about 300 kg) from assembly table to work-bench, and from work-bench to storehouse. Work-bench consists of equipment (including the system for read-out and processing of signals from chambers) providing regular function of three chambers - the one certified and two reference chambers. The certification procedure consists in precious (with tolerance down to 20 mm) evaluation of the signal wire position for every drift tube in the chamber plane. "Translucence" of the chamber set by linear tracks should be done by means of high energy cosmic muons.

In 2000 large volume of management tasks (looking for cost-effective producer, provider of steel blanks, transportation service provider) to provide production of the batch of magnetic cores (fingers) of Tile-Calorimeter was performed. The batch volume is 260 fingers, the weight of one finger is 210 kg. The order was placed at MZOR finally.

Currently production of absorbers (plates made of M1 copper) of electromagnetic liquid argon calorimeter (LAr-Calorimeter) of ATLAS detector is finished at MZOR. New high precision technology of processing of large copper details was developed for this purpose by MZOR technologists in collaboration with JINR specialists and scientists of our laboratory. For example, the thickness of the plate should have tolerance of 0.05mm at the nominal value of 25mm and dimensions 1650x350 mm2. At precent time all absorbers is already fabricated and delivered to JINR-CERN.

Following tasks are being performed by members of the ATLAS-group as a proposal for physical research program of ATLAS detector. The program package ATLFAST, representing mathematical model of the ATLAS detector, is installed on computers of NC PHEP. It is planned to study the process of creation and registration of single W-bosons in ATLAS detector with help of ATLFAST. The purpose of this study is to check theoretical predictions on special role of radiation corrections in this process.

Computation of 3-dimensional differential section of inclusive process of 2-photon creation of lepton pairs in proton-proton interactions is performed. Interest to this process caused by two reasons: first, its differential section increases with increase of energy, and second, it's supposed that it can be used for monitoring of intensiveness of collisions (luminosity) of oncoming beams of LHC.