Speaker
T. Todorov
(CERN/IReS)
Description
The simulation, reconstruction and analysis software access to the
magnetic field has large impact both on CPU performance and on
accuracy.
An approach based on a volume geometry is described. The volumes are
constructed in such a way that their boundaries correspond to field
discontinuities, which are due to changes in magnetic permeability
of the materials. The field in each volume is contiguous.
The field in each volume is interpolated from a regular grid of
values resulting from a TOSCA calculation. In case a
parameterization is available for some volumes it is used instead of
the grid interpolation.
Global access to the magnetic field values requires efficient search
for the volume that contains a global point. An algorithm that
exploits explicitly the layout and the symmetries of the detector is
presented.
The main clients of the magnetic field, which are the simulation
(geant4) and propagation of track parameters and errors in the
reconstruction, can be made aware of the magnetic field volumes by
connecting the per-volume magnetic field providers in their
respective geometries to the corresponding volume in the magnetic
field geometry. In this way the global volume search is
by-passed and the access to the field is sped up significantly.
Authors
N. AMAPANE
(INFN)
T. Todorov
(CERN/IReS)
V. Andreev
(UCLA)
V. Drollinger
(INFN)
V. Karimaki
(HELSINKI-HIP)
V. Klyukhin
(MSU/CERN)
