Tracking and Vertexing in Pile-up Environments Subtask

INFN contribution - Pileup studies in CMS

The INFN activities during year 2011 have been focussed on initial steps towards development of a toolkit to handle high multiplicity events for track reconstruction.
During the Phase I upgrade of the CMS tracker, the full replacement of the Pixel system is an important test bench to study the impact of the high pile-up data on a LHC detector. The upgraded detector should be able to sustain instantaneous luminosities of the order of 2x1034 cm-2s-1; in this environment a more efficient way is needed to manage high particle multiplicity events, especially in pattern recognition for tracking.

Wigner Research Centre for Physics contribution - Detector independent tools for vertexing and particle identification

The aim of the group is to provide detector-independent tools for vertexing and particle identification in high-energy particle physics. The first package (minBiasVertexing) that was written and tested deals with minimum bias vertex finding that is applicable even in a high pile-up environment. It is based on the paper Nucl. Instrum. Meth. A 621 (2010) 526-533. The precise knowledge of position of the primary interaction is crucial for many physics analyses. In case of higher intensity, the performance of the present vertex finders is not sufficient (the longitudinal coordinate of the closest approach to the beam-line is used). With help of advanced mathematical methods, such as fast agglomerative clustering and Gaussian mixture models, both the efficiency and the purity of the measured vertices could be substantially improved.

NTUA contribution - Application of Legendre transformations in pattern recognition for tracking

A new track reconstruction method has been applied in drift tube chambers using the Legendre transform. The method is designed to provide optimum efficiency in muon reconstruction for a broad band of energy cases. Another goal is robustness again noise produced by high cavern background. The method has been studied and will be tested in the case of the monitored drift tube (MDT) chambers of the ATLAS experiment. 

STFC contribution - Track trigger studies

The objective of this element of the work package is to provide a simple and flexible tool to allow the rapid evaluation of a variety of tracking detector layouts, in particular for track triggers. For this purpose, standalone code has been developed that enables flexible definition of silicon detector geometries and the reconstruction of tracks from the simulated hits.