Speakers
Cristina Lazzeroni
(University of Cambridge)Dr
Raluca-Anca Muresan
(Oxford University)
Description
The LHCb experiment will make high precision studies of CP violation and other rare
phenomena in B meson decays. Particle identification, in the momentum range from
~2-100 GeV/c, is essential for this physics programme, and will be provided by two
Ring Imaging Cherenkov (RICH) detectors. The experiment will use several levels of
trigger to reduce the 10MHz rate of visible interactions to the 2kHz that will be
stored. The final level of the trigger has access to information from all
sub-detectors. The standard offline RICH reconstruction involves solving a quartic
equation that describes the RICH optics for each hit in the RICH detector, then using
a global likelihood minimization, combining the information from both RICH detectors
along with tracking information, to determine the best particle hypotheses. This
approach performs well but is vulnerable to background from rings without associated
tracks. In addition, the time needed to run the algorithm is of the order of 100 ms
per event which is to be compared with the time of order 10 ms available to run the
entire final level trigger. Alternative RICH reconstruction algorithms are being
investigated that complement the standard procedure. First, algorithms of greater
robustness, less reliant on the tracking information, are being developed, using
techniques such as Hough transforms and Metropolis Hastings Markov chains. Secondly,
simplified algorithms with execution times of order 3 ms, suitable for use in the
online trigger are being evaluated. Finally, optimal performance requires a
calibration procedure that will enable the performance of the pattern recognition to
be measured from the experimental data. This paper describes the the performance of
the different RICH reconstruction algorithms studied and reports on the strategy for
RICH calibration in LHCb.
Primary authors
Dr
Chris Jones
(Cambridge University)
Cristina Lazzeroni
(University of Cambridge)
Dr
Guy Wilkinson
(Oxford University)
Mitesh Patel
(CERN)
Dr
Raluca-Anca Muresan
(Oxford University)
Roger Forty
(CERN)
