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5. 1 cms physics analysis project Project Leader Veikko Karimäki


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5.1 CMS Physics analysis project

Project Leader Veikko Karimäki


The HIP software and physics project will be replaced from the beginning of 2007 by a new project, the CMS Physics analysis project. After a long-span building of the experiment, in which many of the project members have participated since the beginning of the 1990’s, the CMS experiment will finally start taking data in November 2007. The main goal of the project is to contribute in a significant way to the final software effort before the arrival of data, in order to guarantee fast and efficient calibration of the detector, reconstruction of the events and analysis of the physics channels.
The new all-in-one software package CMSSW is now being tested in terms of the CSA06 computing challenge and the results of the mass productions for simulated events will be available for validation studies in 2007. The HIP CMSSW work include the following major categories in which the project members are active:

-tracker calibration for alignment,

-data intensive Grid computing,


                1. -event reconstruction and selection,

                  1. -CMS User Support and

    1. -physics simulation and analysis.

The studies of physics channels will still be based on simulated events in the year 2007, because the LHC will run at low energy 450+450 GeV. The data will, however, provide good test material to prepare for the analysis of the LHC full energy data. The team will also offer software support for the analysis of the data from the Finnish Cosmic Rack being built and operated by the Tracker project. In addition, the team plays an important role in developing the detector simulation toolkit Geant4.
The project team consists of six PhD physicists (V.Karimäki, R.Kinnunen, K.Lassila-Perini, S.Lehti, T.Lindén and J.Tuominiemi), four PhD students (A.Heikkinen, T.Lampén, J.Nysten and L.Wendland) and an undergraduate student (P.Kaitaniemi). In addition there are two doctoral students adjoint to the project (A.Hector and M.Voutilainen). Three PhD theses (TL, AH and JN) are planned to be completed in 2007.
A more detailed description of the planned activities is given below.
Tracker calibration for alignment

The HIP team has developed and implemented a specific alignment algorithm which is now available and successfully used in the CMSSW package. Further development and testing of the algorithm will continue in 2007. Alignment is Tapio Lampén's doctoral thesis subject and he plans to complete the dissertation within a few months.


Further development of the HIP alignment method will continue. Detailed implemen-tation of the beam and vertex constraints in the algorithm will be studied as well as the implementation of distortions other than simple tilts and offsets, including possible bending of the module wafers and twist effects of the rods and ladders. For the HIP team the first priority is on the Pixel detector alignment. Later in the year the applicability of the algorithm for the CMS strip detectors will be studied.
Data intensive GRID computing

The startup of the Large Hadron Collider (LHC) in 2007 will pose a great challenge for the experiments, which will need to cope with the large data flow from the detectors. The Worldwide Large Hadron Collider Computing Grid (WLCG) collaboration is the infrastructure of computing facilities established for the processing of this data.


The Nordic Data Grid Facility (NDGF) is the distributed grid computing resource in the Nordic countries for the Nordic ALICE, ATLAS, CMS and TOTEM groups as part of the WLCG. The NDGF project was established on a more firm ground in June 2006 with new headquaters in connection with Nordunet, new personnel and funding for 2006-2008. This will enable NDGF to establish itself as a WLCG Tier-1 computing resource. Much work remains for 2007 to accomplish this goal. NDGF has new national coordinators who will coordinate the experiments needs with NDGFs activities. NDGF, the Finnish IT center for science (CSC) and HIP will work on extending, adapting and integrating the ARC middleware with the software frameworks of ALICE, CMS and TOTEM. Another important NDGF activity is the continuing work on interoperability between the ARC, gLite and OSG middleware flavours so that applications can seamlessly use resources on all gridflavours. Participation in this work is crucial to ensure that CMS-services and applications can benefit from the NDGF-resources. Another crucial part of the NDGF activities is to ensure that the needed optical networks are funded and built on top of Nordunet and FUNET.
The pilot CMS resources in Kumpula, the mill- and ametisti- Linux clusters and the silo- and silo2- file servers will be extended with needed CMS services and protocols (SRM implementation, ProdAgent, Frontier SQUID server) to form a functional CMS Tier-2 prototype, that can be transferred to the CSC resources that will become available in 2007. To enable participation in NDGF tests and other similar activities, an upgrade of the M-grid cluster ametisti will be made in 2007, consisting of more disk and CPU. In anticipation of the funding applied from the Ministry of Education for the final computing resources, preparations need to be made with CSC concerning the call for tenders and location of the services to shorten the time between the aqcuisition start and when the resources are available for the end users for the 2008 LHC 14 TeV run.
Event reconstruction and selection

The HIP team has participated under the leadership of Kati Lassila-Perini in the electron/photon working group, which provides the tools to select and reconstruct the electron and photon tracks. These tools have been used to prepare the 1st volume of the Physics TDR in 2006 and they were used in the preparation of the 2nd volume. The activities in this electron/photon working group have been scaled down, apart from the important issue of the analysis of the 2006 electromagnetic calorimeter test beam data which will allow comparision of the simulated and real signal. Another new doctoral thesis is planned to be completed by Jukka Nysten on the subject.


CMS User Support

Kati Lassila-Perini has started as the CMS User Support Coordinator. The task of the User Support is to provide help within the CMS computing and software operations. The User Support Coordinator manages the documentation process and organizes the active user support in form of a web interface and a physical help desk. Regular tutorial sessions for CMS physicists are organized.


For the moment, the CMS software documentation consists of the CMS Workbook which is designed as a first-stop for new users and a CMSSW Reference Manual which is generated automatically from the documentation pages provided by the program developers. Furthermore, much information is provided in separate web pages. In 2007, the CMS Workbook and Reference Manual will be completed and information from scattered web pages will be collected togother in a user manual. A web interface has been setup to allow users to submit questions. In 2007, the functionality of this interface will be evaluated.

Physics simulation and analysis

The main activities will include validation of the CMSSW software for the MSSM Higgs bosons discovery channels H/A-> -> lepton+lepton + X, H/A   -> e +  jet + X, H/A - - 2 -jets + X and H± -  as well as testing of the grid tools and functionality. The team will participate and work in the study groups of the Les Houches 2007 workshop for physics at TeV colliders.


The HIP group will contribute to the new CMSSW software validation by testing the methods for  identification, electron and muon identification, b tagging, top mass reconstruction, ETmiss measurement and Higgs boson mass reconstruction. Sami Lehti has written and will maintain a -tagging package with impact parameter measurement for this software. He continues to work also for an event analysis package, where the analysis can be decoupled from the CMS software environment.
Within the CSA06 project of CMS, the tt and W+jet background process will be analyzed by the HIP group as a test of the use of reconstruction software within the CMS Computing Model. The simulation data available in this project makes also possible the development of background determination algorithms for the heavy MSSM Higgs bosons. The main purpose of the CSA project is to test the functionality of the CMS grid network and tools. During 2007, when the Tier-2 unit at the Finnish IT centre for Science (CSC) in Helsinki is not yet operational, the HIP group is prepared to use the Grid facilities at CERN.
The detailed full simulation work for the A/H -> -> 2 jet channel will be continued by Lauri Wendland for his PhD thesis work. In 2007, b tagging and tagging with  mass reconstruction will be studied in detail to complement the previous studies done with impact parameter and secondary vertex reconstruction methods. The work will culminate in the study of the full selection chain to produce the Higgs boson mass peaks for several Higgs boson masses.

Geant4 development

HIP is a member of the worldwide Geant4 collaboration. In the Oversight Board it is represented by Jorma Tuominiemi. Aatos Heikkinen is the representative of HIP in the Geant4 Steering Board. He also acts as a co-coordinator of the Geant4 hadronic physics package whose development and maintenance is the responsibility of the HIP team.


Pekka Kaitaniemi has joined the project and is preparing his masters thesis which will provide a direct contribution to Geant4 hadronic shower simulation. His main goal is to implement the hadronic codes INCL4 and ABLA in object oriented style. The work will take place in collaboration with Saclay hadronic simulation team.
The team will intensify the Geant4 collaboration with CMS experiment which will offer data for model validation, when the experiment starts in the autumn. Collaboration with other institutes including SLAC computing team, ESA space environment simulation group, INFN Genova group, and Jyväskylä University, will continue. The plan is also to start collaboration with future Space Science Center in Kumpula in the year 2007. The Geant4 activities will yield a new doctoral degree in the year 2007, when Aatos Heikkinen will complete his thesis work.







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