Speaker
Edmund Erich Widl
(Institute for High Energy Physics, Vienna)
Description
The Inner Tracker of the CMS experiment consists of approximately 20,000 sensitive
modules in order to cope with the bunch crossing rate and the high particle
multiplicity expected in the environment of the Large Hadron Collider. For such a big
number of modules conventional methods for track-based alignment face serious
difficulties because of the large number of alignment parameters and the huge
matrices that are involved in the estimation process. For this reason we propose an
iterative (track-by-track) method for track-based global alignment. It is derived
from the Kalman filter and does not require inversions of large matrices. The update
formulas for the alignment parameters and for the associated covariance matrix are
presented. We discuss the implementation and the computational complexity and show
how to limit the latter to an acceptable level. The performance of the method with
respect to precision and speed of convergence is studied in a simplified setup.
Scenarios closer to the CMS experimental setup are studied using a first
implementation within the CMS reconstruction framework ORCA. Results for the barrel
part of the CMS Inner Tracker under these more realistic circumstances are presented.
Primary authors
Edmund Erich Widl
(Institute for High Energy Physics, Vienna)
Rudolf Fruhwirth
(Institute for High Energy Physics, Vienna)
Wolfgang Adam
(Institute for High Energy Physics, Vienna)
