scholarly journals Reconstruction of track candidates at the LHC crossing rate using FPGAs

2020 ◽  
Vol 245 ◽  
pp. 10001
Author(s):  
Giulia Tuci ◽  
Giovanni Punzi
Keyword(s):  
Real Time ◽  
Average Rate ◽  
Computational Effort ◽  
Lhcb Experiment ◽  
Level Trigger ◽  
Full Reconstruction ◽  
Potential Benefits ◽  
Level 1 ◽  
High Level ◽  
New System

In 2021 the LHCb experiment will be upgraded, and the DAQ system will be based on full reconstruction of events, at the full LHC crossing rate. This requires an entirely new system, capable of reading out, building and reconstructing events at an average rate of 30 MHz. In facing this challenge, the system could take advantage of a fast pre-processing of data on dedicated FPGAs. The results of an R&D on these technologies, developed in the context of the LHCb Upgrade I, are presented in this document. In particular, the details and potential benefits of an approach based on producing in real-time sorted collections of hits in the VELO detector (pre-tracks) are discussed. These pre-processed data can then be used as seeds by the High Level Trigger (HLT) farm to find tracks for the Level 1 trigger with much lower computational effort than possible by starting from the raw detector data, thus freeing an important fraction of the power of the CPU farm for higher level processing tasks.

scholarly journals The CMS Trigger Upgrade for the HL-LHC

2020 ◽  
Vol 245 ◽  
pp. 01031
Author(s):  
Thiago Rafael Fernandez Perez Tomei
Keyword(s):  
High Performance ◽  
Second Phase ◽  
Level Trigger ◽  
Cms Experiment ◽  
Rejection Factor ◽  
Reconstruction Software ◽  
Efficient Data ◽  
Level 1 ◽  
High Level ◽  
Selection Algorithms

The CMS experiment has been designed with a two-level trigger system: the Level-1 Trigger, implemented on custom-designed electronics, and the High Level Trigger, a streamlined version of the CMS offline reconstruction software running on a computer farm. During its second phase the LHC will reach a luminosity of 7.5 1034 cm−2 s−1 with a pileup of 200 collisions, producing integrated luminosity greater than 3000 fb−1 over the full experimental run. To fully exploit the higher luminosity, the CMS experiment will introduce a more advanced Level-1 Trigger and increase the full readout rate from 100 kHz to 750 kHz. CMS is designing an efficient data-processing hardware trigger that will include tracking information and high-granularity calorimeter information. The current Level-1 conceptual design is expected to take full advantage of advances in FPGA and link technologies over the coming years, providing a high-performance, low-latency system for large throughput and sophisticated data correlation across diverse sources. The higher luminosity, event complexity and input rate present an unprecedented challenge to the High Level Trigger that aims to achieve a similar efficiency and rejection factor as today despite the higher pileup and more pure preselection. In this presentation we will discuss the ongoing studies and prospects for the online reconstruction and selection algorithms for the high-luminosity era.

scholarly journals CMS trigger performance

2018 ◽  
Vol 182 ◽  
pp. 02037
Author(s):  
Silvio Donato
Keyword(s):  
Computing Time ◽  
Track Reconstruction ◽  
Trigger System ◽  
Drastic Reduction ◽  
Event Selection ◽  
Level Trigger ◽  
Reconstruction Software ◽  
Last Stage ◽  
Level 1 ◽  
High Level

During its second run of operation (Run 2), started in 2015, the LHC will deliver a peak instantaneous luminosity that may reach 2 · 1034 cm-2s-1 with an average pileup of about 55, far larger than the design value. Under these conditions, the online event selection is a very challenging task. In CMS, it is realized by a two-level trigger system: the Level-1 (L1) Trigger, implemented in custom-designed electronics, and the High Level Trigger (HLT), a streamlined version of the offine reconstruction software running on a computer farm. In order to face this challenge, the L1 trigger has been through a major upgrade compared to Run 1, whereby all electronic boards of the system have been replaced, allowing more sophisticated algorithms to be run online. Its last stage, the global trigger, is now able to perform complex selections and to compute high-level quantities, like invariant masses. Likewise, the algorithms that run in the HLT have been greatly improved; in particular, new approaches for the online track reconstruction lead to a drastic reduction of the computing time, and to much improved performances. This document will describe the performance of the upgraded trigger system in Run 2.

scholarly journals Real Time Global Tests of the ALICE High Level Trigger Data Transport Framework

2008 ◽  
Vol 55 (2) ◽  
pp. 703-709 ◽  
Author(s):  
B. Becker ◽  
S. Chattopadhyay ◽  
C. Cicalo ◽  
J. Cleymans ◽  
G. de Vaux ◽  
...  
Keyword(s):  
Real Time ◽  
Data Transport ◽  
Level Trigger ◽  
Global Tests ◽  
High Level

scholarly journals Data analysis at the CMS level-1 trigger: migrating complex selection algorithms from offline analysis and high-level trigger to the trigger electronics

2018 ◽  
Author(s):  
Claudia Wulz ◽  
Gregor Aradi ◽  
Bernhard Arnold ◽  
Herbert Bergauer ◽  
Vasile M. Ghete ◽  
...  
Keyword(s):  
Data Analysis ◽  
Level Trigger ◽  
Offline Analysis ◽  
Level 1 ◽  
High Level ◽  
Selection Algorithms

scholarly journals A real-time FPGA-based cluster finding algorithm for LHCb silicon pixel detector

2021 ◽  
Vol 251 ◽  
pp. 04016
Author(s):  
Giovanni Bassi ◽  
Luca Giambastiani ◽  
Federico Lazzari ◽  
Michael J. Morello ◽  
Tommaso Pajero ◽  
...  
Keyword(s):  
Real Time ◽  
Heterogeneous Computing ◽  
Clustering Algorithm ◽  
General Purpose ◽  
Pixel Detector ◽  
Promising Alternative ◽  
Level Trigger ◽  
High Level ◽  
High Degree ◽  
Algorithm Implementation

Starting from the next LHC run, the upgraded LHCb High Level Trigger will process events at the full LHC collision rate (averaging 30 MHz). This challenging goal, tackled using a large and heterogeneous computing farm, can be eased addressing lowest-level, more repetitive tasks at the earliest stages of the data acquisition chain. FPGA devices are very well-suited to perform with a high degree of parallelism and efficiency certain computations, that would be significantly demanding if performed on general-purpose architectures. A particularly time-demanding task is the cluster-finding process, due to the 2D pixel geometry of the new LHCb pixel detector. We describe here a custom highly parallel FPGA-based clustering algorithm and its firmware implementation. The algorithm implementation has shown excellent reconstruction quality during qualification tests, while requiring a modest amount of hardware resources. Therefore it can run in the LHCb FPGA readout cards in real time, during data taking at 30 MHz, representing a promising alternative solution to more common CPU-based algorithms.

scholarly journals The CMS high level trigger

2014 ◽  
Vol 31 ◽  
pp. 1460297 ◽  
Author(s):  
Valentina Gori
Keyword(s):  
Trigger System ◽  
Output Rate ◽  
Computing Power ◽  
Level Trigger ◽  
Cms Experiment ◽  
Pile Up ◽  
Reconstruction Software ◽  
Physics Performance ◽  
Level 1 ◽  
High Level

The CMS experiment has been designed with a 2-level trigger system: the Level 1 Trigger, implemented on custom-designed electronics, and the High Level Trigger (HLT), a streamlined version of the CMS offline reconstruction software running on a computer farm. A software trigger system requires a tradeoff between the complexity of the algorithms running on the available computing power, the sustainable output rate, and the selection efficiency. Here we will present the performance of the main triggers used during the 2012 data taking, ranging from simpler single-object selections to more complex algorithms combining different objects, and applying analysis-level reconstruction and selection. We will discuss the optimisation of the triggers and the specific techniques to cope with the increasing LHC pile-up, reducing its impact on the physics performance.

scholarly journals The Impact of Applying Wildcards to Disabled Modules for Ftk Pattern Banks on Efficiency and Data Flow

2019 ◽  
Vol 214 ◽  
pp. 01039
Author(s):  
Khalil Bouaouda ◽  
Stefan Schmitt ◽  
Driss Benchekroun
Keyword(s):  
Early Stage ◽  
Hadron Collider ◽  
Track Reconstruction ◽  
Trigger System ◽  
Level Trigger ◽  
Efficiency Losses ◽  
Level 1 ◽  
High Level ◽  
The Impact ◽  
Fast Tracker

Online selection is an essential step to collect the most relevant collisions from the very large number of collisions inside the ATLAS detector at the Large Hadron Collider (LHC). The Fast TracKer (FTK) is a hardware based track finder, built to greatly improve the ATLAS trigger system capabilities for identifying interesting physics processes through track-based signatures. The FTK is reconstructing after each Level-1 trigger all tracks with pT > 1 GeV, such that the high-level trigger system gains access to track information at an early stage. FTK track reconstruction starts with a pattern recognition step. Patterns are found with hits in seven out of eight possible detector layers. Disabled detector modules, as often encountered during LHC operation, lead to efficiency losses. To recover efficiency, WildCards (WC) algorithms are implemented in the FTK system. The WC algorithm recovers inefficiency but also causes high combinatorial background and thus increased data volumes in the FTK system, possibly exceeding hardware limitations. To overcome this, a refined algorithm to select patterns is developed and investigated in this article.

scholarly journals Trigger Rate Monitoring Tools at CMS

2019 ◽  
Vol 214 ◽  
pp. 01047
Author(s):  
Andrew Wightman ◽  
Geoffrey Smith ◽  
Kelci Mohrman ◽  
Charles Mueller
Keyword(s):  
Event Rate ◽  
Trigger System ◽  
Level Trigger ◽  
Cms Experiment ◽  
Trigger Rate ◽  
Monitoring Tools ◽  
Pile Up ◽  
Overall Performance ◽  
Level 1 ◽  
High Level

One of the major challenges for the Compact Muon Solenoid (CMS)experiment, is the task of reducing event rate from roughly 40 MHz down to a more manageable 1 kHz while keeping as many interesting physics events as possible. This is accomplished through the use of a Level-1 (L1) hardware based trigger as well as a software based High-Level Trigger (HLT). Monitoring and understanding the output rates of the L1 and HLT triggers is of key importance for determining the overall performance of the trigger system and is intimately tied to what type of data is being recorded for physics analyses. We present here a collection of tools used by CMS to monitor the L1 and HLT trigger rates. One of these tools is a script (run in the CMS control room) that gives valuable real-time feedback of trigger rates to the shift crew. Another useful tool is a plotting library, that is used for observing how trigger rates vary over a range of beam and detector conditions, in particular how the rates of individual triggers scale with event pile-up.

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