Hadron Calorimeter Research Articles

Brightness and uniformity measurements of plastic scintillator tiles at the CERN H2 test beam

We study the light output, light collection efficiency and signal timing of a variety of organic scintillators that are being considered for the upgrade of the hadronic calorimeter of the CMS detector. The experimental data are collected at the H2 test-beam area at CERN, using a 150 GeV muon beam. In particular, we investigate the usage of over-doped and green-emitting plastic scintillators, two solutions that have not been extensively considered. We present a study of the energy distribution in plastic-scintillator tiles, the hit efficiency as a function of the hit position, and a study of the signal timing for blue and green scintillators.

ATLAS Tile Calorimeter calibration and monitoring systems

The ATLAS Tile Calorimeter is the central section of the hadronic calorimeter of the ATLAS experiment and provides important information for reconstruction of hadrons, jets, hadronic decays of tau leptons and missing transverse energy. This sampling calorimeter uses steel plates as absorber and scintillating tiles as active medium. The light produced by the passage of charged particles is transmitted by wavelength shifting fibres to photomultiplier tubes, located in the outer part of the calorimeter. Neutral particles may also produce a signal after interacting with the material and producing charged particles. The readout is segmented into about 5000 cells, each of them being read out by two photomultipliers in parallel. To calibrate and monitor the stability and performance of each part of the readout chain during the data taking, a set of calibration systems is used. This comprises Cesium radioactive sources, Laser, charge injection elements and an integrator based readout system. Information from all systems allows to monitor and equalise the calorimeter response at each stage of the signal production, from scintillation light to digitisation. Calibration runs are monitored from a data quality perspective and used as a cross-check for physics runs. The data quality efficiency achieved during 2016 was 98.9%. These calibration and stability of the calorimeter reported here show that the TileCal performance is within the design requirements and has given essential contribution to reconstructed objects and physics results.

The next generation of crystal detectors

Crystal detectors have been used widely in high energy and nuclear physics experiments, medical instruments and homeland security applications. Novel crystal detectors are continuously being discovered and developed in academia and in industry. In high energy and nuclear physics experiments, total absorption electromagnetic calorimeters (ECAL) made of inorganic crystals are known for their superb energy resolution and detection efficiency for photon and electron measurements [1]. A crystal ECAL is thus the choice for those experiments where precision measurements of photons and electrons are crucial for their physics missions. Examples are the Crystal Ball NaI(Tl) ECAL, the L3 BGO ECAL and the BaBar CsI(Tl) ECAL in lepton colliders, the kTeV CsI ECAL and the CMS PWO ECAL in hadron colliders and the Fermi CsI(Tl) ECAL in space. For future HEP experiments at the energy and intensity frontiers, however, the crystal detectors used in the above mentioned ECALs are either not bright and fast enough, or not radiation hard enough. Crystal detectors have also been proposed to build a Homogeneous Hadron Calorimeter (HHCAL) to achieve unprecedented jet mass resolution by duel readout of both Cherenkov and scintillation light [2], where development of cost-effective crystal detectors is a crucial issue because of the huge crystal volume required [3]. This contribution discusses several R&D directions for the next generation of crystal detectors for future HEP experiments.

The Atlas Tile Calorimeter experience with 10,000 readout photomultipliers operating since the start of the p-p collisions at LHC

The channels of TileCal, the hadron calorimeter of the ATLAS experiment at the LHC, are read out with 8-stage fine-mesh photomultipliers (PMTs), a special version of the Hamamatsu model R5900. About 10,000 PMTs are operating in TileCal. The PMT response stability allows to calibrate accurately the calorimeter and to achieve high performance of the energy reconstruction of the cells. Currently, no PMT replacement is foreseen before completion of the High Luminosity program of the LHC collider in the next decade. In this perspective, a number of measurements and tests are in progress to qualify the PMT robustness in terms of lifetime and response stability. Data from the Tile calibration procedure for the detector PMTs and from laboratory tests of spare PMTs are being analyzed. Results on PMT failures, gain loss and quantum efficiency loss are presented. Analysis is focused on the study of the observed down-drift with time of the PMT response as a function of the integrated anode charge, and depending on the individual cell exposure to irradiation during the LHC operation. The multi-stage calibration system of Tile and the algorithms adopted to disentangle between gain and quantum efficiency loss are described, as well as the tests performed in dedicated test-benches.

Radiation hardness of Silicon Photomultipliers for CBM@FAIR, NA61@CERN and BM@N experiments

Results of radiation hardness study of Silicon Photomultipliers (SiPMs) to be used at forward hadron calorimeters, including designed Projectile Spectator Detector (PSD) of CBM, PSD of NA61 beyond 2020 upgrade and Zero Degree Calorimeter (ZDC) at BM@N are presented. High intensity beams at future heavy-ion accelerator facilities up to 106∕107 interactions/second will lead to high neutron fluence around calorimeters up to 3×1012 neq/cm2 accumulated during a year of the experiment operation. SiPMs produced by Ketek, Zecotek, Hamamatsu and Sensl manufacturers were irradiated at cyclotron of NPI Rez in a wide range of neutron fluences from 4×1010 up to 6×1012 n/cm2. Change of SiPM’s main parameters after irradiation including dark current, breakdown voltage, noise and signal response to LED was studied in the lab. Furthermore, several packs of irradiated SiPMs were installed at the currently operating NA61 PSD to study the cumulative radiation effect on the calorimeter performance. Beam scan with 20–80 GeV/c protons was performed to determine the dependency of detector energy resolution on beam energy before and after irradiation.

Comparison of Energy Reconstruction Schemes and Different Granularities in the CALICE Scintillator-Steel Analogue Hadron Calorimeter

The CALICE collaboration develops different high-granularity hadronic calorimeter technologies for a future linear collider. These technologies differ in active material, granularity and their readout and thus their energy reconstruction schemes. The Analogue Hadron Calorimeter (AHCAL), based on scintillator tiles with Silicon Photomultiplier readout, measures the signal amplitude of the energy deposition in cells of at most 3 × 3 cm2 size. The Digital, Resistive Plate Chamber (RPC) based, HCAL (DHCAL) detects hits above a certain threshold by firing pad sensors of 1 × 1 cm2. A 2 bit readout is provided by the, also RPC based, Semi-Digital HCAL (SDHCAL), which counts hits above three different thresholds per 1 × 1 cm2 cell. All three calorimeter concepts have been realised in a 1m3 prototype with interleaved Steel absorber and tested at various test beams. This study investigates the impact of the readout, granularity and active medium on the energy resolution individually by applying the reconstruction procedures on AHCAL data, that can also be processed in a way which emulates a (semi-) digital readout system. The difference in granularity is studied via simulations of an AHCAL with 1 × 1 cm2 cell sizes.Additionally, a so-called Software Compensation algorithm is developed to weight hits dependent on their energy content and correct for the difference in the response to the electromagnetic and hadronic sub-showers and thus reduce the influence of fluctuations in the π0 generation. The impact on the energy resolution will be discussed and compared to the other energy reconstruction schemes.

Status and New Results for the sPHENIX Calorimeter Systems

The PHENIX Experiment at RHIC is planning a major upgrade that involves building an entirely new spectrometer, sPHENIX, that is based around the former BaBar solenoid magnet which will enable a comprehensive study of jets and heavy quarkonia in relativistic heavy ion collisions. It will include two new calorimeter systems, one electromagnetic and one hadronic, that will cover an acceptance of ±1.1 units in pseudorapidity and 2π in azimuth. The hadronic calorimeter will be a steel plate scintillating tile design that is read out with wavelength shifting fibers and silicon photomultipliers. It will be divided into two sections: one (the Inner HCAL) will be situated inside the magnet and the other (the Outer HCAL) will be outside the magnet. The electromagnetic calorimeter will be a SPACAL design consisting of a tungsten powder epoxy matrix absorber with embedded scintillating fibers which are also read out with silicon photomultipliers. The design of sPHENIX and its calorimeter systems has made considerable progress over the past several years and is described in this paper. Prototypes of all three calorimeters were built and tested in the test beam at Fermilab in April of 2016, and the first preliminary results from this test, along with a comparison to Monte Carlo simulations, are also discussed.

The NA62 Hadron Calorimeter

NA62 is a fixed target experiment located in the north area of CERN. The ambitious aim of the experiment is the measurement of the branching ratio (Br) of the very rare decay within 10% precision using a decay-in-flight technique. The branching ratio of this decay is very well calculated in the standard model as (9.11 ± 0.72) × 1011 and the measurement of this channel represents one of the most promising fields for the search of new physics beyond the standard model. The presence of just one detectable track in the final state is an enormous challenge for any experiment. The decay is fully reconstructed, which leads to a strong background suppression. Still the detector resolution, combined with the tiny branching ratio of the signal, makes the K+ → μ+ν decay (whose Br is 0.64) a critical source of background. The NA62 detector was therefore designed to perform an excellent π/μ separation using a very efficient particle identification system. A major role is played by the calorimeters that provides a muon rejection factor of the order of 105 through the measurement of energy and shape of the hadronic showers. The calorimetric system consists of an electromagnetic calorimeter filled with liquid krypton and a hadron calorimeter. This presentation, after illustrating the HAC structure, reports on the calibration procedure of the detector response and preliminary results of the performance of the hadronic energy reconstruction.

Challenges of Particle Flow reconstruction in the CMS High-Granularity Calorimeter at the High-Luminosity LHC

The challenges of the High-Luminosity LHC (HL-LHC) are driven by the large number of overlapping proton-proton collisions (pileup) in each bunch-crossing and the extreme radiation dose to detectors at high pseudorapidity. To overcome this challenge CMS is developing an endcap electromagnetic+hadronic sampling calorimeter employing silicon sensors in the electromagnetic and front hadronic sections, comprising over 6 million channels, and highly-segmented plastic scintillators in the rear part of the hadronic section. This High- Granularity Calorimeter (HGCAL) will be the first of its kind used in a colliding beam experiment. Clustering deposits of energy over many cells and layers is a complex and challenging computational task, particularly in the high-pileup environment of HL-LHC. Baseline detector performance results are presented for electromagnetic and hadronic objects, and studies demonstrating the advantages of fine longitudinal and transverse segmentation are explored.

The performance of the CASTOR calorimeter during LHC Run 2

CASTOR is an electromagnetic and hadronic tungsten-quartz sampling Cerenkov calorimeter located at the Compact Muon Solenoid experiment at the Large Hadron Collider. The detector has pseudorapidity borders at -5.2 and -6.6. An overview is presented on the various aspects of CASTOR’s performance and their relations during LHC Run 2. The equalisation of CASTOR’s channels is performed using beam-halo muons. Thereafter, CASTOR’s pedestal spectrum is studied. It is shown that noise estimates which are extracted using a fit, give on average a 10% lower threshold than statistical estimates. Gain correction factors, which are needed for the intercalibration, are obtained using a statistical, in-situ applicable method. The results of this method are shown to be reasonably consistent with laboratory measurements. Penultimately the absolute calibration is discussed, with emphasis on the relation between the scale uncertainty and CASTOR’s alignment. It is shown that the alignment’s contribution to the systematic uncertainty is decreased by over 50% in LHC Run 2 w.r.t. LHC Run 1. Finally generalisations of the conclusions to other subsystems and future improvements are discussed.

DHCAL with minimal absorber: measurements with positrons

In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.

Upgrade of Tile Calorimeter of the ATLAS Detector for the High Luminosity LHC.

The Tile Calorimeter (TileCal) is the hadronic calorimeter of ATLAS covering the central region of the ATLAS experiment. TileCal is a sampling calorimeter with steel as absorber and scintillators as active medium. The scintillators are read out by wavelength shifting fibers coupled to photomultiplier tubes (PMT). The analogue signals from the PMTs are amplified, shaped and digitized by sampling the signal every 25 ns. The High Luminosity Large Hadron Collider (HL-LHC) will have a peak luminosity of 5 × 1034 cm −2 s −1, five times higher than the design luminosity of the LHC. TileCal will undergo a major replacement of its on- and off-detector electronics for the high luminosity programme of the LHC in 2026. The calorimeter signals will be digitized and sent directly to the off-detector electronics, where the signals are reconstructed and shipped to the first level of trigger at a rate of 40 MHz. This will provide a better precision of the calorimeter signals used by the trigger system and will allow the development of more complex trigger algorithms. Three different options are presently being investigated for the front-end electronic upgrade. Extensive test beam studies will determine which option will be selected. Field Programmable Gate Arrays (FPGAs) are extensively used for the logic functions of the off- and on-detector electronics. One hybrid demonstrator prototype module with the new calorimeter module electronics, but still compatible with the present system, may be inserted in ATLAS at the end of 2016.

Polarimetry concept based on heavy crystal hadron calorimeter

In the ongoing JEDI (Jülich Electric Dipole moment Investigations) project, the essential point will be to measure a tiny beam polarization change over an extended period of time. The particle scarcity in the polarized deuteron or proton beams and the required slow extraction rate puts tough experimental constrains on the polarimetry. For the EDM measurements, a dedicated high precision polarimeter is required. To fulfill specifications, a fast, dense, high resolution (energy and time), and radioactive hard novel crystal scintillating material is required. LYSO crystals are supposed to be used as an ideal scintillating material for this kind of detector. The LYSO crystal PMT and SiPM readout, with a FADC based system is under development. The first proton and deuteron beam test of the prototypes are presented here. In this paper, the new polarimetry concept and preliminary results from first proton and deuteron beam time are presented.

Study of TileCal Scintillator Irradiation using the Minimum Bias Integrators

The Tile Calorimeter (TileCal) is the central hadronic calorimeter of the ATLAS experiment at the LHC. It provides precise energy measurements of hadrons, jets, taus and missing transverse energy. The monitoring and calibration of the calorimeter response at each stage of the signal development is done by a movable 137Cs radioactive source, a laser calibration system and a charge injection system. Moreover, during LHC data taking, an integrator-based readout provides the signals coming from inelastic proton-proton collisions at predominantly low momentum transfer (minimum bias events) and allows monitoring of the instantaneous ATLAS luminosity as well as the response of calorimeter cells. The integrator currents have been used to detect and quantify the effect of TileCal scintillator irradiation using the data taken in 2012 and 2015 that correspond to about 22 fb−1 and 4 fb−1 of integrated luminosity, respectively. Finally, the response variation for an irradiated cell has been studied combining the information from three calibration systems (cesium, laser and minimum bias). The result of the irradiation on the TileCal response will be reported.

ATLAS Tile calorimeter calibration and monitoring systems

The ATLAS Tile Calorimeter (TileCal) is the central section of the hadronic calorimeter of the ATLAS experiment and provides important information for reconstruction of hadrons, jets, hadronic decays of tau leptons and missing transverse energy. This sampling calorimeter uses steel plates as absorber and scintillating tiles as active medium. The light produced by the passage of charged particles is transmitted by wavelength shifting fibres to photomultiplier tubes (PMTs), located on the outside of the calorimeter. The readout is segmented into about 5000 cells (longitudinally and transversally), each of them being read out by two PMTs in parallel. To calibrate and monitor the stability and performance of each part of the readout chain during the data taking, a set of calibration systems is used. The TileCal calibration system comprises cesium radioactive sources, Laser and charge injection elements, and allows for monitoring and equalization of the calorimeter response at each stage of the signal production, from scintillation light to digitization. Based on LHC Run 1 experience, several calibration systems were improved for Run 2. The lessons learned, the modifications, and the current LHC Run 2 performance are discussed.

ATLAS Tile Calorimeter time calibration, monitoring and performance

The Tile Calorimeter (TileCal) is the hadronic calorimeter covering the central region of the ATLAS experiment at the LHC. This sampling device is made of plastic scintillating tiles alternated with iron plates and its response is calibrated to electromagnetic scale by means of several dedicated calibration systems.The accurate time calibration is important for the energy reconstruction, non-collision background removal as well as for specific physics analyses. The initial time calibration with so-called splash events and subsequent fine-tuning with collision data are presented. The monitoring of the time calibration with laser system and physics collision data is discussed as well as the corrections for sudden changes performed still before the recorded data are processed for physics analyses. Finally, the time resolution as measured with jets and isolated muons is presented.

The upgraded calibration system for the scintillator-PMT tile hadronic calorimeter of the ATLAS experiment at CERN/LHC

The TileCal section of the hadronic calorimeter of the ATLAS detector at the Large Hadron Collider (LHC), CERN, is a sampling calorimeter employing steel plates as absorber and plastic scintillator tiles read out by photomultiplier tubes (PMTs) as the active medium. We present an overview of the calibration system that enables the TileCal to meet its design goals of sub-1% level accuracy as well as excellent short- and long-term stability through constant monitoring.

Influence of transverse segmentation of back hadronic calorimeter of CMS detector (LHC) on identification of tagging jets in VBF H → τ−τ+ process

Provided here are the results of calculations of tagging jet identification in the process of Higgs boson production via the mechanism of coalescence of vector bosons with subsequent decay into τ-leptons (VBF H→τ−τ+) for different transverse segmentations against the parts of modernized hadronic calorimeter of Compact Muonic Solenoid in the Large Hadron Collider (LHC). The calculations were conducted under conditions of a great number (140) of additionally superposable pp-interactions corresponding to LHC operation mode at high luminosities.

Particle-flow reconstruction and global event description with the CMS detector

The CMS apparatus was identified, a few years before the start of the LHC operation at CERN, to feature properties well suited to particle-flow (PF) reconstruction: a highly-segmented tracker, a fine-grained electromagnetic calorimeter, a hermetic hadron calorimeter, a strong magnetic field, and an excellent muon spectrometer. A fully-fledged PF reconstruction algorithm tuned to the CMS detector was therefore developed and has been consistently used in physics analyses for the first time at a hadron collider. For each collision, the comprehensive list of final-state particles identified and reconstructed by the algorithm provides a global event description that leads to unprecedented CMS performance for jet and hadronic τ decay reconstruction, missing transverse momentum determination, and electron and muon identification. This approach also allows particles from pileup interactions to be identified and enables efficient pileup mitigation methods. The data collected by CMS at a centre-of-mass energy of 8\\TeV show excellent agreement with the simulation and confirm the superior PF performance at least up to an average of 20 pileup interactions.

Processing and Quality Monitoring for the ATLAS Tile Hadronic Calorimeter Data

An overview is presented of Data Processing and Data Quality (DQ) Monitoring for the ATLAS Tile Hadronic Calorimeter. Calibration runs are monitored from a data quality perspective and used as a cross-check for physics runs. Data quality in physics runs is monitored extensively and continuously. Any problems are reported and immediately investigated. The DQ efficiency achieved was 99.6% in 2012 and 100% in 2015, after the detector maintenance in 2013-2014. Changes to detector status or calibrations are entered into the conditions database (DB) during a brief calibration loop between the end of a run and the beginning of bulk processing of data collected in it. Bulk processed data are reviewed and certified for the ATLAS Good Run List if no problem is detected. Experts maintain the tools used by DQ shifters and the calibration teams during normal operation, and prepare new conditions for data reprocessing and Monte Carlo (MC) production campaigns. Conditions data are stored in 3 databases: Online DB, Offline DB for data and a special DB for Monte Carlo. Database updates can be performed through a custom-made web interface.