PhD_StaraWersja Status Report III (1 year)

Supervisor: Dr. Markus Elsing

Start in Austrian Doctoral Student Program: 1st of July 2003

Date: 1s of June 2004

The ATLAS ATC group is headed by Markus Elsing, my supervisor at CERN. One of the main working areas of this group is the development of the ATLAS Inner Detector Software and the physics validation of the ATLAS software in general. The work I have done in the last 12 months covers both activities.

Period: July 2003 - October 2003

The first three months of my PhD_StaraWersja were dominated by the validation of the ATLAS Inner Detector full simulation based on the new simulation engine GEANT4. In an ongoing process, severall releases have been checked against the former GEANT3 simulation using the developed analysis framework. I have also studied the effects on the ATLAS silicon detectors in case of a beam accident that may be caused by a wrong configuration of beam injection magnets. The results of these studies were summarized in an informal note and passed on to the persons in charge.

Period: October 2003 - present

After finishing the GEANT4 validation I started to work on tracking in the ATLAS Inner Detector. The previous simulation studies turned out to be a good preparation for this work, as they gave me a deeper understanding e.g. of the detector geometry and the preparation of the data before entering the reconstruction process.

The overall aim of my work is the study for a high precision W mass measurement for the ATLAS experiment. This topic has been uncovered since the publishing of the ATLAS Physics Technical Design Report (TDR), in which first estimates on the precision of the W mass measurement have been given based on the status of fast simulation at that time. At the time the LHC starts the W mass will be known with a precision of about 30 MeV, combining results from LEP2 and Tevatron. For the ATLAS experiment, a mass resolution of about 15 MeV is predicted by using the leptonic decay channels and the fact that the t-quark-mass will be known with a much higher accuracy than today. A high precision measurement of the W mass will be a very stringest test of the standard model.

As an introduction into this topic, the simulations done for the Physics TDR will be repeated, using the new fast simulation program Athena-Atlfast. In a second step, the work on the realization of an analysis chain will start, with the aim to analyze fully simulated events involving W mass decays. A fully developed analysis frame should then be the base for the W mass measurement using both, fully simulated and future taken data.

Technical realization:

The determination of the total energy scale for leptons in the ATLAS detector is a crucial ingredient for a future W mass measurement. In this scope I have developed an extrapolation package for the track reconstruction that takes the tack propagation in an inhomogeneous magnetic field and multiple scattering respectively energy loss effects into account. This work required - as a first step - the participation in the development of the new Event Data Model (EDM), as the extrapolation package is going to be one major client of the new designed track class package. A first prototype of the track class and the various track parameter representations was released in ATLAS release 7.5.0 in January 2004.

In the following, the complete design of the extrapolation package has been set up. This involved the creation of a new surface description for tracking algorithms, which was developed in close interaction with the developers of the general ATLAS detector description GeoModel. Successively the entire propagation chain was developed including the overall extrapolation tool and propagators for straight line and helical track models. For both cases the appropriate error propagation has been implemented. In close cooperation with Igor Gavrilenko, the author of the ATLAS reconstruction package xKalman, the already existing Runge-Kutta propagation implementation was shifted to the new track extrapolation interface. A similar shift of the already existing iPatRec propagation code is planned. Basic functionallity of the track extrapolation package was introduced with ATLAS release 8.2.0 in Mai 2004, a full functional package is planned to be realeased with ATLAS release 9.0.0 in July.

Combined Testbeam:

The design of the track extrapolation package was done in a modular way such that it can be directly used for the ATLAS Combined Testbeam (CTB) setup (started in May 2004). The testbeam detector setup consists of a simplified detector geometry and a small region constant magnetic field that does not even cover the entire silicon region and therefore turn out to be a good first test structure. The CTB 2004 allows me to test the implemented propagation algorithms and the general interface design with a realistic client and offers me the opportunity to participate in the last ATLAS testbeam data taking before the start of the LHC in 2007.

Future objectives:

3 months timescale:

The major goal for the following months after ATLAS release 9.0.0 will be divided into two realms:

  • The validation of the implemented mathematical algorithms as well as the stability of the software design. This will be done using both, CTB and Data Challenge 2 (started in May 2004) data. An important additional aspect will be the improvement of the embedding of the track extrapolation package into the ATHENA framework and the interaction with client algorithms. Future optimization of the extrapolation package will also be done in respect to time performance.
  • The participation in the development of a material access service and the resulting implementation of multiple scattering and energy loss corrections during the extrapolation process. This will be crucial for the planned future physics study, as the correct respectation of these corrections during the tracking process is - besides the track propagation in the realistic non-uniform magnetic field - the main determining factor for the total energy scale accurancy.

1 year timescale:

The fully developed and validated extrapolation package and an appropriate track fitter that works on top of this package will be the basic requirements for starting the preparation study or a high precision W mass measurement. First steps towards this aim might start in October 2004, depending on the general improvement of the ATLAS offline reconstruction software.


Andreas Salzburger, University of Innsbruck & CERN/PH-ATC

We agree for 12 months extension of the contract as an unpaid associate member of personnel.


Prof. Dietmar Kuhn, University of Innsbruck


Dr. Markus Elsing, CERN/PH-ATC

-- AndreasSalzburger - 13 May 2005
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Topic revision: r3 - 2006-12-16 - JakubMoscicki
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