Track Finder Research Articles

Track reconstruction algorithms for the CBM experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment at the future FAIR accelerator complex at Darmstadt is being designed for a comprehensive measurement of hadron and lepton production in heavy-ion collisions from 8-45 AGeV beam energy, producing events with large track multiplicity and high hit density. The setup consists of several detectors including as tracking detectors the silicon tracking system (STS), the muon detector (MUCH) or alternatively a set of Transition Radiation Detectors (TRD). In this contribution, the status of the track reconstruction software including track finding, fitting and propagation is presented for the MUCH and TRD detectors. The track propagation algorithm takes into account an inhomogeneous magnetic field and includes accurate calculation of multiple scattering and energy losses in the detector material. Track parameters and covariance matrices are estimated using the Kalman filter method and a Kalman filter modification by assigning weights to hits and using simulated annealing. Three different track finder algorithms based on track following have been developed which either allow for track branches, just select nearest hits or use the mentioned weighting method. The track reconstruction efficiency for central Au+Au collisions at 25 AGeV beam energy using events from the UrQMD model is at the level of 93-95% for both detectors.

The CMS Drift Tube Trigger Track Finder

Muons are among the decay products of many new particles that may be discovered at the CERN Large Hadron Collider. At the first trigger level the identification of muons and the determination of their transverse momenta and location are performed by the Drift Tube Trigger Track Finder in the central region of the CMS (Compact Muon Solenoid) experiment, using track segments detected in the Drift Tube muon chambers. Track finding is performed both in pseudorapidity and azimuth. Track candidates are ranked and sorted, and the best four are delivered to the subsequent stage, the Global Muon Trigger, which combines them with candidates found in the two complementary muon systems of CMS, the Resistive Plate Chambers and the Cathode Strip Chambers. The concept, design, control and simulation software as well as tests and the expected performance of the Drift Tube Trigger Track Finder system are described.

Track reconstruction of cosmic ray real data with the CMS Silicon Strip Tracker

The CMS tracking system consists of a silicon pixel vertex detector and a surrounding silicon microstrip detector. The system is currently going through final assembly stage. As the construction goes on, big parts of the detector are being powered, controlled and readout as a whole. A cosmic ray trigger has been setup, thus providing the first real events recorded in the CMS tracker. Reconstruction was performed with three track finder algorithms; we will talk about the Combinatorial Track Finder, which is based on the Kalman Filter technique for both trajectory building and track fitting. A dedicated algorithm for cosmic ray track's seeding has been developed, together with useful tools for the tracking performance analysis; the exercise has been very useful for the understanding and the improvement of the tracking algorithm.

Track reconstruction of real cosmic muon events with CMS tracker detector

The CMS Silicon Strip Tracker (SST) construction has been completed on March 2007. From then to July 2007 the SST has gone through of a long series of tests, involving the cosmic ray data taking. Track reconstruction has been performed with three track finders. We will talk about the so called Combinatorial Track Finder, one of the default CMS track finders, and about its generalization to the cosmic ray case. For the first time this algorithm has been run on real data, both online and offline. Tracking performances on simulated and real data will be discussed.

Trigger system for the TA fluorescence detector

The Telescope Array (TA) is a hybrid detector system consisting of fluorescence detectors (FDs) and a surface detector (SD) array to study ultra high energy cosmic rays. In this paper, we describe the development and status of the trigger system for the TA FDs. The trigger system consists of three components, those are the Signal Digitizer and Finder (SDF) module, the Track Finder (TF) module and the Central Trigger Distributor (CTD) module. The SDF module recognizes the fluorescence signal, TF finds air shower tracks and CTD controls data acquisition. We also report the first engineering run carried out in 2007.

Results of the first integration test of the CMS drift tubes muon trigger

Two drift tubes (DTs) chambers of the CMS muon barrel system were exposed to a 40 MHz bunched muon beam at the CERN SPS, and for the first time the whole CMS Level-1 DTs-based trigger system chain was tested. Data at different energies and inclination angles of the incident muon beam were collected, as well as data with and without an iron absorber placed between the two chambers, to simulate the electromagnetic shower development in CMS. Special data-taking runs were dedicated to test for the first time the Track Finder system, which reconstructs track trigger candidates by performing a proper matching of the muon segments delivered by the two chambers. The present paper describes the results of these measurements.

The "Road Warrior" for the CDF online silicon vertex tracker

The Online Silicon Vertex Tracker (SVT) is a new trigger processor dedicated to the 2-D reconstruction of charged particle trajectories at Level 2 of the CDF trigger. The SVT links the digitized pulse heights found within the Silicon Vertex detector to the tracks reconstructed in the Central Outer Tracker by the Level 1 Fast Track finder. The SVT was recently modified in order to increase its efficiency. The new configuration uses all the Silicon Vertex detector layers. On the other hand the processing time has increased. This can be a problem at higher luminosities of the Tevatron. The "Road Warrior" is a new board that eliminates redundant track candidates before Track Fitting. It is based on the principle of the Associative Memory. The algorithm used is described in the paper, as well as the hardware implementation.

A two-level fanout system for the CDF silicon vertex tracker

The system is part of the new trigger processor Vertex (SVT) dedicated to the reconstruction of charged particle trajectories at the Level 2 of the CDF trigger. The SVT has a maximum event rate of 100 kHz and a latency time of 10 /spl mu/s. Its core is organised as 12 identical systems (slices) running in parallel almost independently. This implementation of the device derives from the geometry of the Silicon Vertex Detector (SVXII) which is divided in 12 identical wedges along the azimuthal angle. Each SVT slice links the digitized pulse heights found within one SVXII wedge to the tracks reconstructed in the corresponding 30/spl deg/ angular region of the Central Outer Tracker (COT) by the Level 1 Fast Track finder (XFT). Since the COT works as a single entity and the XFT tracks are output on a single data stream, their distribution to the proper SVT slices requires a dedicated system. This system is a multi-board project running on a common 20 MHz clock, where the fanout function is performed in two steps by one Fanout A and two Fanout B boards. The architecture, design and implementation of this system are described.

Feasibility study of the CMS first-level muon trigger track finder

We describe a feasibility study for a fast, pipelined first-level muon trigger based on measurements from drift tube chambers for the CMS experiment at LHC. The algorithm, hardware implementation and simulation results for the performance are presented.

Feasibility of the hardware muon trigger track finder processor in CMS

This paper describes a feasibility study for the design of the muon trigger track finder processor in the high-energy physics experiment compact muon solenoid (CMS), planned for 2005, at CERN. It covers the specification, proposed method, and a prototype implementation. Comparison between several other measurement methods and the proposed one are carried out. The task of the processor is to identify muons and measure their transverse momenta and locations within 350 ns. It uses data from almost 200000 detector cells of drift tube muon chambers. The processor searches for muon tracks originating from the Interaction point by joining the track segments provided by the drift tube muon chamber electronics to full tracks. It assigns transverse momentum to each reconstructed track using the track's bend angle.

A drift chamber track finder for the first level trigger of the H1 experiment

The information from the central drift chamber of the H1 experiment is used in a first level trigger to find and count charged tracks, originating from genuine ep collisions at the HERA storage ring. Background processes, predominantly from beam-wall and beam-gas interactions, are discriminated because their distance of closest approach to the collision vertex differs from good events. The track finder is designed in a pipelined fashion, producing decisions at the bunch crossing frequency of ⨍b = 10.4 MHz, however delayed by a fixed decision time of 2.3 μs. This operation is deadtime free but still uniquely related to the specific bunch crossing 24 cycles earlier. The hardware implementation relies on XILINX logic cell arrays which are programmable providing a high flexibility.

A fast track finder for triggering applications in high energy physics

We describe the Monte Carlo simulation results of a trigger processor for high energy physics experiments. This processor performs on-line charged-track pattern recognition at full detector resolution. The simulation results are based on the measured performances of existing prototypes of the two building blocks of the trigger system.

A fast hardware track-finder for the CDF central tracking chamber

We describe the design, construction, and preliminary operation of a hardware track-finder used in the trigger for the Collider Detector at Fermilab (CDF). The track-finder is a 19 stage digital pipeline which uses fast timing information from the central tracking chamber (CTC) to find high momentum tracks. It then transmits information about the tracks to the CDF trigger system for a final decision. The track finder has 8 programmable thresholds between 2.5 and 15 GeV. A search for all high momentum tracks in the central tracking chamber can be completed in an average of 2.5 μs per event. The momentum resolution is δP t/ P t 2 = 3.5%, with a high efficiency that is independent of track density.

Fast track-finding processor based on RAM look-up table for the VENUS detector at KEK

We have developed a fast track-finding processor using signals from the central tracking chamber of the VENUS detector in the TRISTAN experiments. Particle tracks are recognized by a look-up table made with a high-speed static RAM. This method enables us to implement the track finder in the first level triggering. The track finder has been working excellently under heavy background due to synchrotron radiation. A processing time of 110 ns is attained.

Design and construction of the CLEO II drift chamber

We have constructed a new large cylindrical drift chamber (2 m long and 2 m in diameter) for the CLEO II experiment at the Cornell Electron Storage Ring (CESR). The chamber contains 51 readout layers including 11 stereo layers, with 48480 (12240) total (sense) wires. Segmented cathode strips were used instead of field wires for the innermost and outermost layers to provide two accurate measurements of the longitudinal coordinate. Very low density support structures were developed to hold the cathode strips. Aluminum wire was used for the majority of the field wires to reduce multiple scattering and the tension load on the endplates. A semiautomatic apparatus was developed to string wires with the chamber mounted vertically. With this system, it was also possible to replace any wire in the chamber. A maximum stringing rate of 60 wires/h was achieved. The tension on all wires was measured soon after they were strung; the failure rate due to improper tension was typically less than 2%. Hybrid preamplifiers were developed and mounted directly on the chamber on custom printed circuit boards. Each board also contains a pulser calibration system and a high voltage current monitor. High voltage power is individually supplied to each of the 51 layers under computer control. A new type of hardware track finder was developed for the trigger.