1. Introduction

From Letter of Intent for a General-Purpose pp Experiment at the Large Hadron Collider at CERN from October 1 1992 follows: The ATLAS collaboration proposes to build a general purpose proton-proton detector for the Large Hadron Collider, capable of exploring the new energy regime which will become accessible. The detector would be fully operational at the startup of the new accelerator.

The Large Hadron Collider (LHC) offers a large range of physics opportunities, among which the origin of mass at the electroweak scale is a major focus of interest. The detector optimalization is therefore guided by physics issues such as sensitivity to the largest possible Higgs mass range, but also for example by detailed studies of the top quark decays, Supersymmetry searches, and sensitivity to large compositeness scales. The ability to cope with a broad variety of expected physics processes also demonstrates most importantly the detector's potential for unexpected new physics.

Many of the interesting physics questions at the LHC require high luminosity, and so the primary goal of the experiment is to operate at the standard high luminosity for LHC of 1.7.1034 cm-2 s-1
The detector provides as many signatures as possible of new physics using electron, gamma, muon, jet, and missing transverse energy measurements. The Standard Model (SM) Higgs search can be used as a first benchmark for the detector optimalization.

The basic design considerations of the detector

are:

  • very good electromagnetic calorimetry for electron and photon identification and measurements, complemented by hermetic jet and missing ET calorimetry;
  • efficient tracking at high luminosity for lepton momentum measurements and for enhanced electron and photon identification, and tau and heavy flavour tagging capabilities at lower luminosity;
  • precision muon momentum measurements with stand-alone capatibility at highest luminosity.

    • The choice of specific detector subsystems is based on the results and extrapolations from R & D activities. Our group took participation in R & D 33 project: A Highly Segmented and Compact Liquid Argon Calorimeter for the LHC - The TGT Calorimeter - . See also Nucl.Instrum.Meth.A357:333-343,1995.
    This project was oriented to develop a new highly segmented and compact liquid argon calorimeter dedicated for LHC programme. In this project we contributed with the development of the sum and cold front end electronics and by Monte-Carlo studies.

    ATLAS management decision concerning to the end-cap area was following: the end-cap subdetectors will be completed from two detectors, working slightly on the different principes: EMEC (ElectroMagnetic End-Cap) calorimeter which is based on the accordion technology and HEC (Hadronic End-Cap) one, which use so called "electrostatic transformer" read-out cells - see chapter 3.