General broken lines as advanced track fitting method Kleinwort, Claus
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2012, Letnik:
673
Journal Article
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In HEP experiments the description of the trajectory of a charged particle is obtained from a fit to measurements in tracking detectors. The parameterization of the trajectory has to account for ...bending in the magnetic field, energy loss and multiple scattering in the detector material. General broken lines implement a track model with the proper description of multiple scattering leading to linear with a special structure of the corresponding matrix allowing for a fast solution with the computing time depending linearly on the number of measurements. The calculation of the full covariance matrix along the trajectory enables the application to track based alignment and calibration of large detectors with global methods.
The alignment of the Belle II tracking system, composed of a pixel and strip vertex detectors and central drift chamber, is described by approximately sixty thousand parameters; from local alignment ...of sensors and wires to relative global alignment of the sub-detectors.
In the next data reprocessing, scheduled since Spring 2021, we aim to determine all parameters in a simultaneous fit by Millepede II, where recent developments allow to achieve a direct solution of the full problem in about one hour and make it practically feasible for regular detector alignment.
The tracking detectors and the alignment technique are described and the alignment strategy is discussed in the context of studies on simulations and experience obtained from recorded data. Preliminary results and further refinements based on studies of real Belle II data are presented.
The inner silicon detector of the Compact Muon Solenoid experiment (CMS) at CERNʼs LHC consists of 16 588 modules. Charged-particle tracks in the detector are used to improve the accuracy to which ...the position and orientation of the modules are known. This contribution focuses on the Millepede-II algorithm, one of the two alignment algorithms used by CMS. Recently an advanced track model has been introduced into the CMS alignment procedure, which is based on the “Broken Lines” model and is able to take multiple Coulomb scattering in the detector material properly into account. We show the unique approach needed for solving the alignment problem in a reasonable amount of time. Emphasis is given to the mathematical treatment of the problem.
The complex system of the CMS all-silicon tracker detector, with 15
148 silicon strip and 1440 silicon pixel modules, requires sophisticated alignment procedures. In order to achieve an optimal ...track-parameter resolution, the position and orientation of its modules need to be determined with a precision of few micrometers. The alignment of pixel modules is crucial for the analyses requiring a precise vertex reconstruction. The aligned geometry is based on the analysis of several million reconstructed tracks recorded during the commissioning of the CMS experiment, both with cosmic rays and with the first proton–proton collisions. Statistical precision of the alignment of the modules with respect to the particle trajectories to less than
10
μ
m
has been achieved. The results have been validated by several data-driven studies and compared with predictions obtained from a detailed detector simulation.
Recent developments include the determination of sensor bow and displacements between sensors of composite modules and are presented here for the first time.
Ideas on improving future detectors with respect to alignment are given.
Track finding at Belle II Bertacchi, Valerio; Bilka, Tadeas; Braun, Nils ...
Computer physics communications,
02/2021, Letnik:
259
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This paper describes the track-finding algorithm that is used for event reconstruction in the Belle II experiment operating at the SuperKEKB B-factory in Tsukuba, Japan. The algorithm is designed to ...balance the requirements of a high efficiency to find charged particles with a good track parameter resolution, a low rate of spurious tracks, and a reasonable demand on CPU resources. The software is implemented in a flexible, modular manner and employs a diverse selection of global and local track-finding algorithms to achieve an optimal performance.
In HEP experiments the description of the trajectory of a charged particle is obtained from a fit to measurements in tracking detectors. The parametrization of the trajectory has to account for ...bending in the magnetic field, energy loss and multiple scattering in the detector material. General broken lines implement a track model with proper description of multiple scattering leading to linear equations with a special structure of the corresponding matrix allowing for a fast solution with the computing time depending linearly on the number of measurements. The calculation of the full covariance matrix along the trajectory enables the application to track based alignment and calibration of large detectors with global methods.
A high-resolution beam telescope is one of the most important and demanding infrastructure components at any test beam facility. Its main purpose is to provide reference particle tracks from the ...incoming test beam particles to the test beam users, which allows measurement of the performance of the device-under-test (DUT). \LYCORIS, a six-plane compact beam telescope with an active area of \(\sim\)10\(\times\)\SI{10}{\square\centi\metre} (extensible to 10\(\times\)\SI{20}{\square\centi\metre}) was installed at the \DIITBF in 2019, to provide a precise momentum measurement in a \SI{1}{\tesla} solenoid magnet or to provide tracking over a large area. The overall design of \LYCORIS will be described as well as the performance of the chosen silicon sensor. The \SI{25}{\micro\metre} pitch micro-strip sensor used for \LYCORIS was originally designed for the \SID detector concept for the International Linear Collider. It adopts a second metallization layer to route signals from strips to the bump-bonded \KPIX ASIC and uses a wire-bonded flex cable for the connection to the DAQ and the power supply system. This arrangement eliminates the need for a dedicated hybrid PCB. Its performance was tested for the first time in this project. The system has been evaluated at the \DIITBF in several test-beam campaigns and has demonstrated an average single-point resolution of \SI{7.07}{\micro\meter}.
The physics goals the Belle II experiment require an exceptionally good alignment of all the components of the Belle II tracker. The Belle II tracker is composed of the DEPFET based pixel silicon ...detector, four layers of double sided silicon strip detector, a low material budget drift chamber, all three operating in a solenoidal 1.5 T B field, which is affected by the final focusing system of the accelerator. Each component of these three components must be aligned with an accuracy significantly better than the point resolution of the detector that for the PXD is order of 10 microns. The Belle II alignment software is based on the Millepede II package and uses cosmics and collision data to constrain the weak modes. The performance of the alignment algorithms was tested on the phase 2 collision data collected during spring 2018. Good alignment of the vertex detector was essential to demonstrate the nano-beam collision scheme of the accelerator and check the quality of the impact parameter resolution, which is essential for time-dependent CP violation studies at the B factory.
EUTelescope is a modular, comprehensive software framework for the reconstruction of particle trajectories recorded with beam telescopes. Its modularity allows for a flexible usage of processors each ...fulfilling separate tasks of the reconstruction chain such as clustering, alignment and track fitting. %The reconstruction chain is directed via XML steering files. The framework facilitates the usage of any position sensitive device for both the beam telescope sensors as well as the device under test and supports a wide range of geometric arrangements of the sensors. In this work, the functionality of the EUTelescope framework as released in v2.2 and its underlying dependencies are discussed. Various use cases with emphasis on the General Broken Lines advanced track fitting methods give examples of the work flow and capabilities of the framework.
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