Activity 1.1 - The ATLAS experiment at LHC
A. Aloisio*, M.G. Alviggi, M. Biglietti, V. Canale, M. Caprio, G. Carlino*, F. Cevenini, G. Chiefari,
F. Conventi, R. De Asmundis*, M. Della Pietra, D. Della Volpe*, A. Doria*, P. Iengo, L. Merola, A.
Migliaccio, S. Patricelli, G. Sehkniaidze*
ATLAS is an experiment approved by CERN, based on a worldwide collaboration,
that will run at the LHC (Large Hadron Collider) and allow to study proton-proton
interactions at 7 + 7 TeV in the center of mass system. The experiment has been
designed to cope with the enormous discovery potential that will be accessible by
this new accelerator. It will be possible to discover the Higgs Boson up to the highest
masses in the SM (Standard Model) and in the MSSM (Minimal Supersymmetric
Standard Model), study the properties of the top quark, CP violation in the Bo
system, search for super-symmetric particles and possible signals for physics beyond
the Standard Model (new vector bosons, quark and lepton compositness, etc.). The
first physic run is now foreseen in 2007 at a luminosity of 1033 cm-2s-1.
The maximum machine luminosity (1034 cm-2s-1) with interactions every 25 ns,
requires the use of detectors at the limit of today’s technological possibilities. The
Naples group will contribute, in collaboration with the Universities of Lecce and
Rome “Tor Vergata” to the construction of the RPC detectors which will generate
trigger signal for muon particles originating from the interaction point with the
possibility to select their momentum.
The system will have roughly 3.500 m2 of detectors built with two gas gaps, each
equipped with two planes of strips readout electrodes in orthogonal directions with
more than 400.000 digital readout channels and will achieve a time resolution of few
ns and a space resolution of the order of one cm. RPCs will work in proportional
mode with low detected charge (1pC) to allow the efficient performance also at the
high counting rates foreseen in the LHC cavern. The full system will require the
construction of roughly 1.100 mechanically independent units.
The Naples group has the responsibility to construct the trigger detectors and the data
read-out system for all electronic channels via a fast link and, on the software side,
the responsibility, together with other groups, of the packages of simulation of the
first level trigger system and of reconstruction of the muon tracks in the detector.
Through all the 2004 we continued with the massive production of all RPC types has
and the cosmic rays tests in the test station in our laboratory. 8 RPC chambers are
tested simultaneously. A total of 70% of the Atlas RPC has been tested and shipped
at Cern. All characteristics of components used to assemble units are inserted in a
production database which has been developed by our group.
In the ATLAS experiment the trigger chambers (RPCs) are assembled together with
the drift tube precision chamber (MDTs) to form the stations of the muon
spectrometer. In 2004 this new activity started in CERN and consisted in the final
cabling (signals, services, etc…) and the mechanical integration RPC-MDT. After
the unit is assembled a dedicated test procedure (gas leak, cosmic rays, etc…) has
been set up to certify the station before installation in the ATLAS experiment.
In 2004 we have been involved in two test beams at CERN. In the first, at the GIF
facilities, we study the ageing of the RPC irradiated simultaneously both by photons
produced in the decays of a Cesium source and by an high energy proton beam. In
the second, with a high energy muon beam derived from the CERN SPS and with the
25ns bunch structure as in LHC, we study the performances of a complete slice of
the muon spectrometer. The relevance of this test was the almost final configuration
of the system from the front-end electronics (trigger and DAQ ) to the complete
analysis chain (reconstruction, etc…). This test-beam activity was fundamental to
finalize the design of the optical link for the level 1 muon trigger and for the RPC
data read-out.
On software and computing activity we continued to collaborate with the Rome1
group to study level 1 muon trigger algorithms with high statistic samples and with
the Lecce group for the development of the code for muon reconstruction in ATLAS
and its implementation as event filter at the third level of the trigger using OO/C++
programming language. The Naples group has:
been responsible for the continuous upgrade of the RPC detector layout description
in order to optimize trigger efficiencies at low and high pT;
designed and written the OO/C++ code production for the trigger simulation
program studying in details the performances of the system;
a major role in the developing of the muon reconstruction packages: the stand-alone
track reconstruction in the spectrometer (Moore) , the combined reconstruction
matching with the track reconstructed in the inner detector (Muid) and the on-line
version of the package used as event filter (trigmoore);
set-up a local computing farm as Tier2 prototype, according to the worldwide
distributed computing model adopted by LHC collaborations and participated to the
two phases of the Atlas Data Challenge 1 2 consisting in the simulation,
reconstruction and analysis of a sample of physical data.
Program for 2005
During 2005 the activities involving the group will be the:
completion of the mass production of all detectors and their quality certification
with cosmic rays tests in Naples;
continuation of the assembly at CERN of integrated muon stations (RPC+ MDT);
start of installation of muon stations on the experiment down in the ATLAS pit;
set-up of commissioning for the muon trigger system (detector working point,
monitoring, efficiencies, noise, etc…);
finalization of simulation studies for the level 1 trigger with Roma I group. The
simulation code in C++ has been completed and studies on the noise contamination
and on the validation of the physical events produced are foreseen;
development and validation of the muon reconstruction software algorithms in
ATLAS with a large variety of simulated physical events both at off-line level and as
event filter at the third trigger level;
participation, using the Napoli Farm upgraded to Tier-2, at the ATLAS Data
Challenge 3 consisting in the simulation, reconstruction and analysis of large sample
of physical events using now all the new tools of the Atlas Software. In particular the
services provided by the Athena Framework and by the Grid tools. The data
simulation will be done in the framework of Geant 4, the Object Oriented version of
Geant 3. We will study in particular super-symmetric events and decays of the Z
boson in two muons.