Electromagnetic Calorimeter Trigger Research Articles

ECAL trigger performance in Run 2 and improvements for Run 3

The CMS electromagnetic calorimeter (ECAL) is a high resolution crystal calorimeter operating at the CERN LHC. It is read out at 40 MHz (the proton-proton collision rate) in order to provide information to the hardware-level (Level-1) trigger system, which decides whether the full CMS detector must be read out for each collision. The ECAL trigger performance achieved during LHC Run 2 (2015-2018) will be presented. The increased luminosity with respect to the LHC Run 1 has required frequent calibrations during LHC operation to account for radiation-induced changes in crystal and photodetector response. Further improvements in the energy and time reconstruction of the CMS ECAL trigger primitives are being explored for LHC Run 3 (2022-24), using additional features implemented in the on-detector readout. In this presentation, we will review the ECAL trigger performance during LHC Run 2 and present improvements to the ECAL trigger system for LHC Run 3.

ECAL trigger performance in Run 2 and improvements for Run 3

The CMS electromagnetic Calorimeter (ECAL) is a high resolution crystal calorimeter operating at the CERN LHC. It is responsible for the identification and precise reconstruction of electrons and photons in CMS, which were crucial in the discovery and subsequent characterization of the Higgs boson. It also contributes to the reconstruction of tau leptons, jets, and calorimeter energy sums, which are vital components of many CMS physics analyses. The ECAL trigger system employs fast digital signal processing algorithms to precisely measure the energy and timing information of ECAL energy deposits recorded during LHC collisions. These trigger primitives are transmitted to the Level-1 trigger system at the LHC collision rate of 40 MHz. These energy deposits are then combined with information from other CMS sub-detectors to determine whether the event should trigger the readout of the data from CMS to be transmitted to the High-Level Trigger and eventually to permanent storage. This note will summarize the ECAL trigger performance achieved during LHC Run 2 (2015–2018). It will describe the methods that are used to provide frequent calibrations of the ECAL trigger primitives during LHC operation. These are needed to account for radiation-induced changes in crystal and photodetector response and to maintain stable trigger rates and efficiencies up to 0|η|=3.. They also minimize the spurious triggering on direct signals in the photodetectors used in the barrel region (|η|<1.48). Both of these effects have increased relative to LHC Run 1 (2009–2012), due to the higher luminosities experienced in Run 2. Further improvements in the energy and time reconstruction of the CMS ECAL trigger primitives are being explored for LHC Run 3 (2021–2023), using additional features implemented in the on-detector readout. These are particularly focused on improving the performance at the highest instantaneous luminosities (which will reach or exceed 2⋅ 1034 cm−2 s−1 in Run 3) and in the most forward regions of the calorimeter (|η|>2.5), where the effects of detector aging will be the greatest. The main features of these improved algorithms will be described and preliminary estimates of the expected performance gains will be presented.

Status of the Electromagnetic Calorimeter Trigger system at the Belle II experiment

The Belle II experiment at the SuperKEKB collider in Japan has been under the construction toward a physics run in 2018 with an ultimate target of 40 times higher instantaneous luminosity than the KEKB collider. The main physics motivation is to search for the New Physics from heavy quark/lepton flavor decays. In order to select an event of interest efficiently under much higher luminosity and beam background environment than the KEKB, we have upgraded the Electromagnetic Calorimeter (ECL) hardware trigger system. It would be realized by the improvement of ECL trigger logic based on two main triggers, the total energy and the number of clusters, with an FPGA-based flexible architecture and a high speed serial link for the data transfer. We report the current status of hardware, firmware, and software that has been achieved so far. The overall scheme of the system will be presented as well.

Natrium: Use of FPGA embedded processors for real-time data compression

We present test results and characterization of a data compression system for the readout of the NA62 liquid krypton calorimeter trigger processor. The Level-0 electromagnetic calorimeter trigger processor of the NA62 experiment at CERN receives digitized data from the calorimeter main readout board. These data are stored on an on-board DDR2 RAM memory and read out upon reception of a Level-0 accept signal. The maximum raw data throughput from the trigger front-end cards is 2.6 Gbps. To readout these data over two Gbit Ethernet interfaces we investigated different implementations of a data compression system based on the Rice-Golomb coding: one is implemented in the FPGA as a custom block and one is implemented on the FPGA embedded processor running a C code. The two implementations are tested on a set of sample events and compared with respect to achievable readout bandwidth.

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

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

CMS Electromagnetic Trigger commissioning and first operation experiences

The CMS electromagnetic calorimeter (ECAL) is a high-resolution calorimeter made of 75848 lead tungstate crystals and optimized for the discovery of the Higgs boson in its two photon decay mode. In view of the high raw event rate at the Large Hadron Collider, the ECAL Trigger will play a major role. This paper reviews the strategy and the tests completed to ensure that the ECAL Trigger reaches the required specifications. The results from the commissioning and the first experiences with cosmic ray data are presented.

Electromagnetic calorimeter trigger at Belle

The performance of CsI(Tl) electromagnetic calorimeter trigger system in the Belle experiment is described. Two kinds of trigger schemes have been taken into account, namely a total energy trigger and a cluster counting trigger which are complementary to each other. In addition, the system has provided the online/offline luminosity information using the Bhabha event trigger scheme. An upgrade of the trigger is discussed.

Beam tests of a prototype level-1 calorimeter trigger for LHC experiments

Beam tests of a first-prototype electromagnetic calorimeter trigger processor for LHC experiments are described. The synchronous, pipelined, digital processor built with ASICs, was successfully operated at the full LHC bunch-crossing frequency of 40 MHz. Real data signals were obtained from a liquid argon electromagnetic calorimeter. The measured performance of the electron/photon trigger algorithm is compared with Monte Carlo simulations.