Speaker
Mr
Leonard Koch
(JLU Giessen)
Description
In the near future, the Belle~II experiment at the SuperKEKB
accelerator at KEK in Tsukuba, Japan, will start operation at a
luminosity a factor $40$ higher than its predecessor experiment,
Belle. The physics program includes the search for physics beyond the
Standard Model of particle physics by the investigation of $CP$
violating processes and rare $B$ meson decays. Many important decay
channels involve $K_S^0$ mesons.
The detector features two layers of silicon pixel cells closest to the
interaction point surrounded by four layers of double sided silicon
strip detectors. Due to the high backgoround level, the expected
occupancy of the Pixel Detector reaches up to $3\,\%$ requiring an
online data reduction system: Using the four layers of strip detectors
and the surrounding detectors, the online reconstructed tracks of
charged particles are extrapolated to the pixelated layers, where
Regions of Interest (ROIs) are defined around the intercepts. Only
the pixel data inside these ROIs are stored. Thus, particles creating
an insufficient number of hits in the outer detectors are not
reconstructed and subsequntly no regions of interest are created,
resulting in the loss of the related hits in the Pixel Detector. The
particles creating a sufficient number of hits in all six layers, but
not in the outer four, are lost as well.
In this contribution, an online tracking algorithm is presented
focusing on the reconstruction of charged pions from displaced
vertices, the characteristic decay topology of $K_S^0$ mesons. All six
layers are used, in order to prevent the pixel data of the above
mentioned particles to be lost. The algorithm is based on the fast
Hough transform applied to the hits mapped onto the conformal plane.
The amount of background is reduced by a two stage neural network
filtering system.
Primary author
Mr
Leonard Koch
(JLU Giessen)
Co-authors
Jens Sören Lange
(Herr)
Wolfgang Kuehn
(JLU Giessen)
