PhD_StaraWersja Status Report II (6 months)

Supervisor: Dr. Markus Elsing

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

Date: 16th of January 2004

The ATLAS ATC group is headed by Markus Elsing, my supervisor at CERN. One of the general working areas of this group is the development of the ATLAS Inner Detecter software and the physics validation of the ATLAS software in general.

The first 4 months

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.

The last 2 months and future plans

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 f.e. 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 precise 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 full simulated events involving W mass decays. A fully developed analysis frame should then be the base for the W mass measurement using both, full simulated and future taken data.

The study on the W mass measurement will mainly involves two persons: Wolfgang Liebig, who is fellow in ATC and me.

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 am developing an extrapolation package for the track reconstruction that takes the propagation in an inhomogeneous magnetic field and multiple scattering respectively energy loss effects into account. This work required - as a first step - the participantation 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.

What is following is the development of a prototype track extrapolation package, that allows to port the already existing propagation algorithms of the two ATLAS Inner Detector reconstruction packages iPat and xKalman. The extrapolation package should work as an reconstruction AlgTool in the Athena framework, the underlying software framework used for event generation, simulation and reconstruction in ATLAS. A crucial part of the design process is to implement a modular pattern, like it was also suggested in the final report of the ATLAS Reconstruction Task Force (RTF). On one hand, this will introduce a higher level of compatibility between existing reconstruction and tracking algorithms in the ATLAS reconstruction software, and on the other hand it will guarantee the possibility of extending the track extrapolation package by various specif propagation algorithms.

Combined Testbeam:

Parallel to the development of the track extrapolation package that is used for the offline reconstruction, a similar track extrapolation setup for the ATLAS Combined Testbeam (starting end of April 2004) will be developed, allowing tests of the implemented propagation algorithms and the general interface design with a realistic client and will offer me the opportunity to participate in the last ATLAS testbeam data taking before the start of the LHC in 2007. The planed testbeam setup will consist 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.

6 months time scale:

The time scale for releasing a complete track extrapolation package is release ATLAS 9.0.0, in June 2004. Within this release, the reconstruction packages of the ATLAS offline reconstruction are mend to use the new EDM classes internally and therefore make use of the new track extrapolation interface as well. The optimization in respect of precision and timing performance can then (and in earlier development releases) be done in an iterative process.

-- AndreasSalzburger - 13 May 2005

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Topic revision: r2 - 2006-12-16 - JakubMoscicki
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