Speaker
Simon Taylor
(Jefferson Lab)
Description
The future GlueX detector in Hall D at Jefferson Lab is a large acceptance (almost 4pi) spectrometer
designed to facilitate the study of the excitation of the gluonic field
binding quark--anti-quark pairs into mesons.
A large solenoidal magnet will provide a 2.2-Tesla field that will be used
to momentum-analyze the charged particles emerging from a liquid hydrogen
target. The trajectories
of forward-going particles will be measured with a set of
four planar cathode strip drift chamber packages with six layers per package.
The design naturally separates the track into segments where the magnetic
field is relatively constant, thereby opening up the possibility of performing
local helical fits to the data within individual packages. We have
implemented the Riemann Helical Fit algorithm to fit the track
segments.
The Riemann Helical Fit is a fast and elegant algorithm combining a circle fit
for determining the transverse momentum and a line fit for determining the dip angle and
initial z value that does not require computation of any derivative matrices.
The track segments are then linked together by swimming through the field from
one package to the next to form track candidates. A comparison between
the Riemann Circle Fit and a simple linear regression method that assumes that
the origin is on the circle will be presented. A comparison between
the Riemann Helical Fit and a full least-squares fit with a non-uniform
magnetic field will also be presented.
Author
Simon Taylor
(Jefferson Lab)
