Endcap Calorimeter Research Articles

CMS Upgrades with a focus on detector technologies

In 2026 the Large Hadron Collider after its upgrade will provide an instantaneous luminosity of 5÷7×1034 cm2s−1, which is three times higher than the nominal luminosity. The so-called High Luminosity LHC will be in operation for about ten years. Such a long operation means that detectors will be exposed to a very high irradiation dose. These two factors - the high instantaneous luminosity and the large irradiation dose - require more robust and higher granularity detectors and significantly faster data transmission and analysis. To face these challenges the CMS detector will be significantly upgraded in the coming years. It is planned to completely rebuild the tracker system, endcap calorimeters and install a new MIP (minimum ionizing particle) timing detector. In this paper a brief review of the CMS detector upgrades will be given, with more details on the tracker, the calorimeters and the timing detector.

A High-Granularity Timing Detector (HGTD) for the Phase-II upgrade of the ATLAS detector

The expected increase of the particle flux at the high-luminosity phase of the LHC (HL-LHC) with instantaneous luminosities up to L = 7.5× 1034 cm−1s−1 will have a severe impact on the ATLAS detector performance. The pile-up is expected to increase on average to 200 interactions per bunch crossing. The reconstruction and trigger performance for electrons, photons as well as jets and transverse missing energy will be severely degraded in the end-cap and forward region, where the liquid Argon based electromagnetic calorimeter has coarser granularity and the inner tracker has poorer momentum resolution compared to the central region. A High Granularity Timing Detector (HGTD) is proposed in front of the liquid Argon end-cap calorimeters for pile-up mitigation and for bunch per bunch luminosity measurements. This device should cover the pseudo-rapidity range of 2.4 to about 4.0. Two Silicon sensors double-sided layers are foreseen to provide a precision timing information for minimum ionizing particle with a time resolution better than 50 pico-seconds per hit (i.e. 30 pico-seconds per track) in order to assign the particle to the correct vertex. Each readout cell has a transverse size of 1.3 mm×1.3 mm leading to a highly granular detector with about 3 millions of readout electronics channels. Low-Gain Avalanche Detector (LGAD) technology has been chosen as it provides an internal gain good enough to reach large signal over noise ratio needed for excellent time resolution. Extensive LGAD research and development (R&D) campaigns are carried out to investigate the suitability of this new technology as timing sensors for HGTD. The related readout ASIC is also being studied extensively.

Erratum: Dose rate effects in the radiation damage of the plastic scintillators of the CMS hadron endcap calorimeter

Erratum: Dose rate effects in the radiation damage of the plastic scintillators of the CMS hadron endcap calorimeter

Learning representations of irregular particle-detector geometry with distance-weighted graph networks

We explore the use of graph networks to deal with irregular-geometry detectors in the context of particle reconstruction. Thanks to their representation-learning capabilities, graph networks can exploit the full detector granularity, while natively managing the event sparsity and arbitrarily complex detector geometries. We introduce two distance-weighted graph network architectures, dubbed GarNet and GravNet layers, and apply them to a typical particle reconstruction task. The performance of the new architectures is evaluated on a data set of simulated particle interactions on a toy model of a highly granular calorimeter, loosely inspired by the endcap calorimeter to be installed in the CMS detector for the High-Luminosity LHC phase. We study the clustering of energy depositions, which is the basis for calorimetric particle reconstruction, and provide a quantitative comparison to alternative approaches. The proposed algorithms provide an interesting alternative to existing methods, offering equally performing or less resource-demanding solutions with less underlying assumptions on the detector geometry and, consequently, the possibility to generalize to other detectors.

The CMS High Granularity Calorimeter for High Luminosity LHC

The CMS experiment at CERN will undergo significant improvements during the Phase-II Upgrade to operate with a 10-fold increase in luminosity and the associated event pileup of the High Luminosity LHC (HL-LHC). The forward calorimetry will be exposed to very high radiation levels and the CMS collaboration is designing a new calorimeter, the High Granularity Calorimeter (CE), to replace the existing endcap calorimeters. It will have higher transverse and longitudinal segmentation for both electromagnetic (CE-E) and hadronic (CE-H) sections to facilitate particle-flow reconstruction. The fine structure of showers can be measured and used to enhance particle identification, whilst still achieving good energy resolution. The CE-E, and a large fraction of CE-H, will be based on hexagonal silicon sensors produced from 8-inch wafers, each with several hundreds of individual cells of 0.5 – 1 cm2 cell size. The remainder of the CE-H will be based on highly-segmented scintillators read out with SiPMs. The overview of the CE project presented in this paper is focused on the silicon sensors covering motivation, engineering design, expected performance and the current status of prototypes, from lab measurements to beam tests.

The CMS High Granularity Calorimeter for HL-LHC

Calorimetry in high-energy physics is rapidly evolving, with new challenges and a wide variety of technologies being employed, both for signal creation and detection. Advances in large-area highly-segmented detectors are providing possibilities for high-granularity calorimetry. The CMS HGCAL, being designed to replace the existing CMS endcap calorimeters for the HL-LHC era, is one example. It is a sampling calorimeter, featuring unprecedented transverse and longitudinal readout segmentation for both electromagnetic (CE-E) and hadronic (CE-H) compartments. This will facilitate particle-flow calorimetry, where the fine structure of showers can be measured and used to enhance pileup rejection and particle identification, whilst still achieving good energy resolution. The CE-E and a large fraction of CE-H will use hexagonal silicon sensors as active detector material. The lower-radiation environment will be instrumented with scintillator tiles with on-tile SiPM readout. An overview of the HGCAL project will be presented, covering motivation, engineering design, readout and trigger concepts, and performance in simulation.

Beam-tests of prototype modules for the CMS High Granularity Calorimeter at CERN

As part of its HL-LHC upgrade program, CMS is developing a High Granularity Calorimeter (HGCAL) to replace the existing endcap calorimeters. The HGCAL will be realised as a sampling calorimeter, including 36 layers of silicon pads and 16 layers combining both silicon+scintillator detectors interspersed with metal absorber plates. Starting from 2016, prototype modules, based on 6-inch hexagonal silicon pad sensors with pad areas of 1.0 cm2, have been constructed. In 2017 and 2018, beam tests of different sampling configurations made from these modules have been conducted at CERN's SPS using beams of charged hadrons and electrons with momenta from 20 to 350 GeV/c. The setup was complemented with CALICE's AHCAL prototype, a scintillator-based sampling calorimeter, mimicking the proposed design of the HGCAL's scintillator part. Most importantly, the new Skiroc2-CMS readout ASIC has been used in the silicon modules, facilitating the study of its timing capabilities in practice. This talk summarises the test beam efforts in 2017 and 2018. Preliminary results, including gain characterisation, calibration with minimum ionising particles and energy reconstruction performance of electron induced showers are shown.

ARRAY: An open source, modular and probe-card based system with integrated switching matrix for characterisation of large area silicon pad sensors

Silicon pad sensors are proposed as active material in highly granular sampling calorimeters of future collider experiments such as the Compact Linear Collider (CLIC) or the International Linear Collider (ILC). The electromagnetic section of these designs often include O(1000 m$^2$) of silicon pad sensors. For the luminosity measurement, a dedicated forward calorimeter called LumiCal is foreseen. More recently, the CMS experiment has decided to adopt the same concept in its endcap calorimeter upgrade for the HL-LHC. The sensors are typically produced from 6- or 8-inch wafers and consist of a few hundred smaller cells, each with an area of O(0.1 to 1 $\text{cm}^2$). For the prototyping phase of these projects, several design choices have to be evaluated while for mass production, thousands of sensors have to be tested for quality control. For the electrical characterisation of these sensors, it is important to bias them under realistic conditions. To fulfil these requirements, ARRAY, a compact, modular and cost efficient system for large area silicon pad sensor characterisation has been developed and successfully commissioned. It consists of two plugin printed circuit boards: an active switching matrix with 512 input channels that holds all controls and a passive probe card that connects to the sensor. The latter can then be adapted to any sensor geometry. All design files are open source. The system has been used to measure currents ranging from 500 pA to 5 $\mu$A and capacitances between 5 pF and 100 pF. A precision of better than 0.2 pF on capacitance measurements in that range can be achieved. Examples of calibration and measurement results for leakage current and capacitance are presented.

First results from the CMS SiPM-based hadronic endcap calorimeter

The CMS hadronic calorimeter employs a plastic-scintillator-based endcap detector. In early 2017, a 20° wedge of the endcap was upgraded with silicon photomultipliers (SiPMs) and readout electronics based on the QIE11 digitizer. Based on the excellent experience with this 20° pilot system in 2017, the entire endcap detector was upgraded with SiPMs in early 2018. We report on the first ever operation of SiPMs in a high-rate collider detector.We compare SiPM performance to that of the previous hybrid photodiode / QIE8-based readout and describe how the factor three improvement in photon-detection efficiency, increased longitudinal segmentation, and improved response stability allow for mitigation of scintillator radiation damage and simplified calibration. We report in situ measurements of radiation-induced SiPM dark current. Overall, we show that the upgraded SiPM-based system brings more than 50% improvement in radiation-induced response degradation.

Construction of the Forward Endcap Calorimeter of the PANDA Experiment at FAIR

PANDA is the main hadron physics addressing experiment of the future FAIR (Facility for Antiproton and Ion Research) center at Darmstadt, Germany. Located at the HESR antiproton storage ring the PANDA detector is optimized for physics of the weak and strong interactions in the charm sector: Search for new and exotic states of matter, precise determination of quantum numbers, masses and widths of hadronic resonances and deeper insights into the structure of hadrons. The detector consists of a target spectrometer built around the interaction region, where antiprotons carrying momenta of 1.5-15 GeV/c collide with a fixed hydrogen target, and a forward spectrometer. Its design is based on compactness and cost saving while achieving high resolution, rate capability and physics selectivity. In the PANDA target spectrometer the electromagnetic calorimeter is composed of three subdetectors based on lead tungstate crystals operated at −25° C. A barrel structure built from 11360 crystals will be closed in up- and downstream direction by two endcaps containing 524 and 3856 crystals, respectively. After intense beam test phases with a 200 crystal forward endcap prototype the required performance was shown to be met and the design finished. The upstream located forward endcap is currently under construction. Besides the overall mechanical design and cooling concept the 16-crystal submodules series manufacturing and quality assurance measures are presented.

The CMS high granularity calorimeter for the high luminosity LHC

The CMS (Compact Muon Solenoid) experiment at CERN will undergo significant improvements during the Phase-II Upgrade to cope with a 10-fold increase in integrated luminosity with the HL-LHC (High Luminosity Large Hadron Collider) era. The forward calorimetry faces very high radiation levels and pileup in the detectors. The CMS collaboration is designing a highly granular calorimeter to replace the existing endcap calorimeters (CE). It features unprecedented transverse and longitudinal segmentation for both electromagnetic (CE-E) and hadronic (CE-H) parts. This will facilitate Particle Flow Algorithms (PFAs), where the structure of showers can be measured and used to enhance pileup rejection and particle identification, whilst still achieving good energy resolution. The CE-E and a large fraction of CE-H will use hexagonal silicon sensors produced from 200 mm (8 inch) wafers, with 192 (432) cells of 1 cm 2 (0.5 cm 2 ) size. The rest of the CE-H uses highly-segmented scintillator tiles with on-tile SiPM (Silicon Photomultiplier) readout. An overview of the HGCal (High Granularity Calorimeter) project is presented in this paper with a focus on the silicon sensors. We cover motivation, engineering design, expected performance and the current status of prototypes.

Silicon Calorimeters

We review the development of silicon-based calorimeters from the very first applications of small calorimeters used in collider experiments to the large-scale systems that are being designed today. We discuss silicon-based electromagnetic calorimeters for future e− e+ colliders and for the upgrade of the CMS experiment's endcap calorimeter to be used in the high-luminosity phase of the LHC. We present the intrinsic advantages of silicon as an active detector material and highlight the enabling technologies that have made calorimeters with very high channel densities feasible. We end by discussing the outlook for further extensions to the silicon calorimeter concept, such as calorimeters with fine-pitched pixel detectors.

First beam tests of prototype silicon modules for the CMS High Granularity Endcap Calorimeter

The High Luminosity phase of the Large Hadron Collider will deliver 10 times more integrated luminosity than the existing collider, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry. As part of its upgrade program, the Compact Muon Solenoid collaboration is designing a high-granularity calorimeter (HGCAL) to replace the existing endcap calorimeters. It will feature unprecedented transverse and longitudinal readout and triggering segmentation for both electromagnetic and hadronic sections. The electromagnetic section and a large fraction of the hadronic section will be based on hexagonal silicon sensors of 0.5–1 cm2 cell size, with the remainder of the hadronic section being based on highly-segmented scintillators with silicon photomultiplier readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection. First hexagonal silicon modules, using the existing Skiroc2 front-end ASIC developed for CALICE, have been tested in beams at Fermilab and CERN in 2016. We present results from these tests, in terms of system stability, calibration with minimum-ionizing particles and resolution (energy, position and timing) for electrons, and the comparisons of these quantities with GEANT4-based simulation.

Construction and beam-tests of silicon and scintillator-SiPM modules for the CMS High Granularity Calorimeter for HL-LHC

A High Granularity Calorimeter (HGCAL) is being designed to replace the existing endcap calorimeters in CMS for the HL-LHC [1] era. It features unprecedented transverse and longitudinal segmentation for both electromagnetic (CE-E) and hadronic (CE-H) compartments, with silicon sensors being chosen for the high-pseudorapidity regions due to their radiation tolerance. The remainder of the HGCAL, in the lower radiation environment, will use plastic scintillator with on-tile SiPM readout. Prototype hexagonal silicon modules, featuring a new Skiroc2-CMS front-end chip, together with a modified version of the scintillator-SiPM CALICE AHCAL, have been built and tested in beams at CERN in 2017. In this paper, we present measurements of noise, calibration, shower shapes and performance with electrons, pions and muons.

Calibration of the CMS hadron calorimeter in Run 2

Various calibration techniques for the CMS Hadron calorimeter in Run 2 and the results of calibration using 2016 collision data are presented. The radiation damage corrections, intercalibration of different channels using the phi-symmetry technique for barrel, endcap and forward calorimeter regions are described, as well as the intercalibration with muons of the outer hadron calorimeter. The achieved intercalibration precision is within 3%. The in situ energy scale calibration is performed in the barrel and endcap regions using isolated charged hadrons and in the forward calorimeter using the Zarrow ee process. The impact of pileup and the developed technique of correction for pileup is also discussed. The achieved uncertainty of the response to hadrons is 3.4% in the barrel and 2.6% in the endcap region (at the pseudorapidity range |η|<2) and is dominated by the systematic uncertainty due to pileup contributions.

A High-Granularity Timing Detector for the Phase-II upgrade of the ATLAS calorimeter system: detector concept description and first beam test results

The expected increase of the particle flux at the high luminosity phase of the LHC (HL-LHC) with instantaneous luminosities up to 7.5⋅1034 cm−2s−1 will have a severe impact on the ATLAS detector performance. The pile-up is expected to increase on average to 200 interactions per bunch crossing. The reconstruction performance for electrons, photons as well as jets and transverse missing energy will be severely degraded in the end-cap and forward region. A High Granularity Timing Detector (HGTD) is proposed in front of the liquid Argon end-cap and forward calorimeters for pile-up mitigation. This device should cover the pseudo-rapidity range of 2.4 to about 4.0. Low Gain Avalanche Detectors (LGAD) technology has been chosen as it provides an internal gain good enough to reach large signal over noise ratio needed for excellent time resolution. The requirements and overall specifications of the High Granular Timing Detector at the HL-LHC will be presented as well as the conceptual design of its mechanics and electronics. Beam test results and measurements of irradiated LGAD silicon sensors, such as gain and timing resolution, will be shown.

Electronics and triggering challenges for the CMS High Granularity Calorimeter

The High Granularity Calorimeter (HGCAL), presently being designed by the CMS collaboration to replace the CMS endcap calorimeters for the High Luminosity phase of LHC, will feature six million channels distributed over 52 longitudinal layers. The requirements for the front-end electronics are extremely challenging, including high dynamic range (0.2 fC–10 pC), low noise (∼2000 e− to be able to calibrate on single minimum ionising particles throughout the detector lifetime) and low power consumption (∼20 mW/channel), as well as the need to select and transmit trigger information with a high granularity. Exploiting the intrinsic precision-timing capabilities of silicon sensors also requires careful design of the front-end electronics as well as the whole system, particularly clock distribution. The harsh radiation environment and requirement to keep the whole detector as dense as possible will require novel solutions to the on-detector electronics layout. Processing the data from the HGCAL imposes equally large challenges on the off-detector electronics, both for the hardware and incorporated algorithms. We present an overview of the complete electronics architecture, as well as the performance of prototype components and algorithms.

Construction and beam-tests of silicon-tungsten prototype modules for the CMS High Granularity Calorimeter for HL-LHC

As part of its HL-LHC upgrade program, CMS is developing a High Granularity Calorimeter (HGCAL) to replace the existing endcap calorimeters. The HGCAL will be realised as a sampling calorimeter, including an electromagnetic compartment comprising 28 layers of silicon pad detectors with pad areas of 0.5–1.0 cm2 interspersed with absorbers. Prototype modules, based on 6-inch hexagonal silicon pad sensors with 128 channels, have been constructed and include many of the features required for this challenging detector. In 2016, beam tests of sampling configurations made from these modules have been conducted both at FNAL and at CERN using the Skiroc2 front-end ASIC (designed by the CALICE collaboration for ILC). In 2017, the setup has been extended with CALICE's AHCAL prototype, a scinitillator based sampling calorimeter, and it was further tested in dedicated beam tests at CERN. There, the new Skiroc2-CMS front-end ASIC was used for the first time. We highlight final results from our studies in 2016, including position resolution as well as precision timing-measurements. Furthermore, the extended setup in 2017 is discussed and first results from beam tests with electrons and pions are shown.

The CMS High Granularity Calorimeter for the High Luminosity LHC

The High Luminosity LHC (HL-LHC) will integrate 10 times more luminosity than the LHC, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry, and hallmarks the issue for future colliders. As part of its HL-LHC upgrade program, the CMS collaboration is designing a High Granularity Calorimeter to replace the existing endcap calorimeters. It features unprecedented transverse and longitudinal segmentation for both electromagnetic (ECAL) and hadronic (HCAL) compartments. This will facilitate particle-flow calorimetry, where the fine structure of showers can be measured and used to enhance pileup rejection and particle identification, whilst still achieving good energy resolution. The ECAL and a large fraction of HCAL will be based on hexagonal silicon sensors of 0.5–1 cm2 cell size, with the remainder of the HCAL based on highly-segmented scintillators with silicon photomultiplier (SiPM) readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection.

Large-area hexagonal silicon detectors for the CMS High Granularity Calorimeter

During the so-called Phase-2 Upgrade, the CMS experiment at CERN will undergo significant improvements to cope with the 10-fold luminosity increase of the High Luminosity LHC (HL-LHC) era. Especially the forward calorimetry will suffer from very high radiation levels and intensified pileup in the detectors. For this reason, the CMS collaboration is designing a High Granularity Calorimeter (HGCAL) to replace the existing endcap calorimeters. It features unprecedented transverse and longitudinal segmentation for both electromagnetic (CE-E) and hadronic (CE-H) compartments. The CE-E and a large fraction of CE-H will consist of a sandwich structure with silicon as active detector material. This paper presents an overview of the ongoing sensor development for the HGCAL and highlights important design features and measurement techniques. The design and layout of an 8-inch silicon sensor prototype is shown. The hexagonal sensors consist of 235 pads, each with an area of about 1 cm2. Furthermore, Synopsys TCAD simulations regarding the high voltage stability of the sensors for different geometric parameters are performed. Finally, two different IV characterisation methods are compared on the same sensor.