Calorimeter Trigger Research Articles

A Digital Trigger for the Electromagnetic Calorimeter at the COMPASS Experiment

At the COMPASS experiment at CERN's SPS many physics channels containing neutral particles are studied. These particles are identified by two electromagnetic calorimeters covering different regions of transverse momentum. For certain physics the main signature is described by these neutral particles requiring a calorimetric trigger system. The method described here is based on the existing front end electronics and uses digital pulse shape analysis techniques. With this approach a flexible trigger system was implemented. Because no new hardware had to be produced, the development costs were minimized. The implementation of the trigger as well as the performance, measured during the 2009 run will be discussed.

The ATLAS Liquid Argon Calorimeter at the LHC: Overview and Performance

Liquid Argon (LAr) Calorimeters provide electromagnetic and forward hadronic calorimetry measurements for the ATLAS experiment. Since 2008, all parts of the LAr calorimeters are read out. An overview of the LAr calorimeters, including hardware status and performance of the calibration system and calorimeter trigger, is presented. Results on timing alignment, uniformity and energy flow, extracted from cosmics and collision data, are presented. They indicate excellent performance of the LAr calorimeters 3 months after the start of LHC operation at 7 TeV energy in the center of mass.

ATLAS level-1 calorimeter trigger hardware: initial timing and energy calibration

The ATLAS Level-1 Calorimeter Trigger identifies high-pT objects in the Liquid Argon and Tile Calorimeters with a fixed latency of up to 2.5μs using a hardware-based, pipelined system built with custom electronics. The Preprocessor Module conditions and digitizes about 7200 pre-summed analogue signals from the calorimeters at the LHC bunch-crossing frequency of 40 MHz, and performs bunch-crossing identification (BCID) and deposited energy measurement for each input signal. This information is passed to further processors for object classification and total energy calculation, and the results are used to make the Level-1 trigger decision for the ATLAS detector. The BCID and energy measurement in the trigger depend on precise timing adjustments to achieve correct sampling of the input signal peak. Test pulses from the calorimeters were analysed to derive the initial timing and energy calibration, and first data from the LHC restart in autumn 2009 and early 2010 were used for validation and further optimization. The results from these calibration measurements are presented.

A novel calorimeter trigger concept: The jet trigger of the H1 experiment at HERA

We report on a novel trigger for the liquid argon calorimeter which was installed in the H1 Experiment at HERA. This trigger, called the “Jet Trigger”, was running at level 1 and implemented a real-time cluster algorithm. Within only 800 ns, the Jet Trigger algorithm found local energy maxima in the calorimeter, summed their immediate neighbors, sorted the resulting jets by energy, and applied topological conditions for the final level 1 trigger decision. The Jet Trigger was in operation from the year 2006 until the end of the HERA running in the summer of 2007. With the Jet Trigger it was possible to substantially reduce the thresholds for triggering on electrons and jets, giving access to a largely extended phase space for physical observables which could not have been reached in H1 before. The concepts of the Jet Trigger may be an interesting upgrade option for the LHC experiments.

The performance of the ATLAS Level-1 Calorimeter Trigger with LHC collision data

The ATLAS first-level calorimeter trigger is a hardware-based system designed to identify high-ET jets, electron/photon and τ candidates and to measure total and missing ET in the ATLAS calorimeters. After more than two years of commissioning in situ with calibration data and cosmic rays, the system has now been used extensively to select the most interesting proton-proton collision events. Fine tuning of timing and energy calibration has been carried out in 2010 to improve the trigger response to physics objects. In these proceedings, an analysis of the performance of the level-1 calorimeter trigger is presented, along with the techniques used to achieve these results.

Design of a Electromagnetic Calorimeter Trigger System for the Belle II Experiment

Design of a Electromagnetic Calorimeter Trigger System for the Belle II Experiment

Upgrading the ATLAS Level-1 Calorimeter Trigger using topological information

The ATLAS Level-1 Calorimeter Trigger (L1Calo) is a fixed latency, hardware-based pipelined system designed for operation at the LHC design luminosity of 1034cm−2s−1. Plans for a several-fold luminosity upgrade will necessitate a complete replacement for L1Calo (Phase II). But backgrounds at or near design luminosity may also require incremental upgrades to the current L1Calo system (Phase I). This paper describes a proposed upgrade to the existing L1Calo to add topological algorithm capabilities, using Region of Interest (RoI) information currently produced by the Jet and EM/Hadron algorithm processors but not used in the Level-1 real-time data path.

Upgrade of the PreProcessor system for the ATLAS level-1 calorimetertrigger

The ATLAS Level-1 Calorimeter Trigger is a hardware-based pipelinedsystem designed to identify high-PT objects in the ATLAScalorimeters within a fixed latency of 2.5 us. It consists of threesubsystems: the PreProcessor which conditions and digitises analoguesignals and two digital processors. The majority of the PreProcessor's tasks are performed on a dense Multi-Chip Module(MCM) consisting of FADCs, a time-adjustment and digital processing ASICs, and LVDS serialisers designed and implemented in ten year old technologies.An MCM substitute, based on today's components (dual channel FADCs and FPGA), is being developed to enhance the flexibility of the digitalprocessing and to profit from state-of-the-art electronics. The development andfirst test results are presented.

A demonstrator for a level-1 trigger system based on MicroTCA technology and 5Gb/s optical links

A demonstrator for the CMS Level-1 calorimeter trigger system has been designed, manufactured, tested and a time-multiplexed trigger implemented. The prototype card uses the AMC double width form factor, 5Gb/s links and a Xilinx XC5VTX150T or XC5VTX240T FPGA. A possible implementation of such a trigger architecture in CMS is described.

The ATLAS Calorimeter Trigger Commissioning Using Cosmic Ray Data

While waiting for the first LHC collisions, the ATLAS detector is undergoing integration exercises performing cosmic ray data taking runs. The ATLAS calorimeter trigger software uses a common framework capable of retrieving, decoding and providing data to different particle identification algorithms. This work reports on the results obtained during the first data-taking period of 2009 with the calorimeter trigger. Experts from detector areas such as calorimetry, data flow management, data quality monitoring and the trigger worked together to reach stable data taking conditions. Issues like noise readout channels were addressed and the global trigger robustness was evaluated.

ATLAS high level calorimeter trigger software performance for cosmic ray events

The ATLAS detector is undergoing intense commissioning effort with cosmic rays preparing for the first LHC collisions late 2009. Combined runs with all of the ATLAS subsystems are being taken in order to evaluate the detector performance. This is an unique opportunity also for the trigger system to be studied with different detector operation modes, such as different event rates and detector configuration. The ATLAS trigger starts with a hardware based system which tries to identify detector regions where interesting physics objects may be found (eg: large transverse energy depositions in the calorimeter system). An accepted event will be further processed by more complex software algorithms at the second level where detailed features are extracted (full detector granularity data for small portions of the detector is available). Events accepted at this level will be further processed at the so-called event filter level. Full detector data at full granularity is available for offline-like processing with complete calibration to achieve the final decision. This year we could extend our experience by including more algorithms at the second level and event filter calorimeter trigger. Clustering algorithms for electrons, photons, taus, jets and missing transverse energy are being commissioned during this combined run period. We report the latest results for such algorithms. Issues such as hot calorimeter regions identification, processing time for the algorithms, data access (specially at the second level) are being evaluated. Intense usage of online and quasi-online (during offline reconstruction of runs) monitoring helps to trace and fix problems.

Performance of the CMS Global Calorimeter Trigger

The CMS Global Calorimeter Trigger system performs a wide-variety of calorimeter data processing functions required by the CMS Level-1 trigger. It is responsible for finding and classifying jets and tau-jets, calculating total and missing transverse energy, total transverse energy identified within jets, sorting e/γ candidates, and calculating several quantities based on forward calorimetry for minimum-bias triggers. The system is based on high-speed serial optical links and large FPGAs. The system has provided CMS with calorimeter triggers during commissioning and cosmic runs throughout 2008. The performance of the system in validation tests and cosmic runs is presented here.

The liquid argon jet trigger of the H1 Experiment at HERA

We report on a novel calorimeter trigger for the H1 Experiment at HERA, called the “Jet Trigger”. This trigger was running at level 1 and implemented a real-time cluster algorithm. Within only 800ns, the Jet Trigger finds local energy maxima in the calorimeter, sums their immediate neighbors, sorts the resulting “jets” by energy, and applies topological conditions for the final level 1 trigger decision. The Jet Trigger has operated since the year 2006 until the end of the HERA running in the summer of 2007. With the Jet Trigger it was possible to substantially reduce the thresholds for triggering on electrons and jets.

Level-2 Calorimeter Trigger Upgrade at CDF

The CDF Run II level 2 calorimeter trigger is implemented in hardware and is based on a simple algorithm that was used in Run I. This system has worked well for Run II at low luminosity. As the Tevatron instantaneous luminosity increases, the limitation due to this simple algorithm starts to become clear. As a result, some of the most important jet and MET (missing ET) related triggers have large growth terms in cross section at higher luminosity. In this paper, we present an upgrade of the L2CAL system which makes the full calorimeter trigger tower information directly available to the level 2 decision CPU. This upgrade is based on the Pulsar, a general purpose VME board developed at CDF and already used for upgrading both the level 2 global decision crate and the level 2 silicon vertex tracking. The upgrade system allows more sophisticated algorithms to be implemented in software and both level 2 jets and MET can be made nearly equivalent to offline quality, thus significantly improving the performance and flexibility of the jet and MET related triggers. This is a natural expansion of the already-upgraded level 2 trigger system, and is a big step forward to improve the CDF triggering capability at level 2. This paper describes the design, the hardware and software implementation and the performance of the upgrade system.

Triggering with the LHCb calorimeters

The LHCb experiment at the LHC has been conceived to pursue high precision studies of CP violation and rare phenomena in b hadron decays. The online selection is crucial in LHCb and relies on the calorimeters to trigger on high transverse energy electrons, photons, π0 and hadrons. In this purpose a dedicated electronic has been realized. The calorimeter trigger system has been commissioned and is used to trigger on cosmic muons before beams start circulating in the LHC. When the LHC will start, it will also provide a very useful interaction trigger.

The CDF level 2 calorimetric trigger upgrade

CDF II upgraded the calorimeter trigger to cope with the higher detector occupancy due to the increased Tevatron instantaneous luminosity ( ∼ 2.8 × 10 32 cm - 2 s - 1 ) . While the original system was implemented in custom hardware and provided to the L2 trigger a limited-quality jet clustering performed using a reduced resolution measurement of the transverse energy in the calorimeter trigger towers, the upgraded system provides offline-quality jet reconstruction of the full resolution calorimeter data. This allows to keep better under control the dependence of the trigger rates on the instantaneous luminosity and to improve the efficiency and purity of the trigger selections. The upgraded calorimeter trigger uses the general purpose VME board Pulsar, developed at CDF II and already widely used to upgrade the L2 tracking and L2 decision systems. A battery of Pulsars is used to merge and send the calorimeter data to the L2 CPUs, where software-implemented algorithms perform offline-like clustering. In this paper we review the design and the performance of the upgraded system.

Test beam operation of the CMS calorimeter trigger synchronization boards

The CMS experiment uses information from its electromagnetic and hadronic calorimeters and muon detectors to decide whether to read out the whole detector. For such a task to be successful, all trigger primitives pushed through the trigger decision tree must be flawlessly aligned in time for operation at 40 MHz. Both calorimeters in CMS use the Synchronization Link Board for this purpose. In this article we report on the test results of this board using the bunched beams available in the H4 electron beam line at CERN.

The ATLAS Level-1 Calorimeter Trigger

The ATLAS Level-1 Calorimeter Trigger usesreduced-granularity information from all the ATLAS calorimeters tosearch for high transverse-energy electrons, photons, τ leptons andjets, as well as high missing and total transverse energy. Thecalorimeter trigger electronics has a fixed latency of about 1 μs,using programmable custom-built digital electronics. This paperdescribes the Calorimeter Trigger hardware, as installed in the ATLASelectronics cavern.

Commissioning Experience With the ATLAS Level-1 Calorimeter Trigger System

The ATLAS Level-1 Calorimeter Trigger is one of the main elements of the first stage of event selection for the ATLAS experiment at the LHC. The input stage consists of a mixed analogue/digital component taking trigger sums from the ATLAS calorimeters. The trigger logic is performed in a digital, pipelined system with several stages of processing, largely based on FPGAs, which perform programmable algorithms in parallel with a fixed latency to process about 300 Gbyte/s of input data. The real-time output consists of counts of different types of physics objects and energy sums. The production of final modules started in 2006, and installation of these modules and the necessary infrastructure at ATLAS has been underway for some time, with the intention of having a full system in situ during 2007, before first collisions at the LHC. The first experiences of commissioning and running the full scale system will be presented, along with results from integration tests performed with the upstream calorimeters, and the downstream trigger and data flow systems.

Design and implementation of the new D0 level-1 calorimeter trigger

Increasing luminosity at the Fermilab Tevatron collider has led the D0 collaboration to make improvements to its detector beyond those already in place for Run IIa, which began in March 2001. One of the cornerstones of this Run IIb upgrade is a completely redesigned level-1 calorimeter trigger system. The new system employs novel architecture and algorithms to retain high efficiency for interesting events while substantially increasing rejection of background. We describe the design and implementation of the new level-1 calorimeter trigger hardware and discuss its performance during Run IIb data taking. In addition to strengthening the physics capabilities of D0, this trigger system will provide valuable insight into the operation of analogous devices to be used at LHC experiments.