arXiv:2306.16325v2 [physics.ins-det] 1 Jul 2023

Simulation results of a New type of sandwich
calorimeter, Double readout Sandwich
Calorimeter (DSC) performance
T. Takeshita1 and R. Terada1
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Department of Physics, Faculty of Science, Shinshu University
July 4, 2023

Abstract
In this study, we propose a novel fully active total absorption calorimeter with enhanced readout capabilities through fine splitting. The proposed calorimeter employs a sandwich structure composed of scintillator
glasses and lead glasses, which are subdivided into small tiles. This configuration enables the creation of a finely segmented three-dimensional
calorimeter that is compatible with Particle Flow Algorithms (PFA). This
article presents a comprehensive description of the calorimeter design
and reports performance results obtained through simulations. Notable,
calorimeter demonstrates exceptional linearity and energy resolution, closely
rivaling that of homogeneous calorimeters. The simulated pcalorimeter
achieves an impressive energy resolution of approximately 9%/ E(GeV).

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Introduction

Future high-energy experiments in particle physics necessitate substantial advancements in the energy resolution of hadron calorimeters. Whilehomogeneous calorimeters constructed from a single material are known
for their excellent energy resolution, they face challenges related to lighttransmission, radiation-tolerance, segmentation, and cost [1]. In thisstudy, we propose a novel approach to address these challenges by introducing a fully active, three-dimensional segmented calorimeter employing
two similar materials: scintillator glass and lead glass which has cost advantage. By combining these materials in a sandwich structure, we aim toachieve a finely segmented calorimeter that maintains high energy resolution while mitigating the limitations associated with large homogeneous
calorimeters. While these materials bear few distinctions, the scintillator
glass measures energy through scintillation light, whereas the lead glass,excels in detecting Cerenkov light, which is directory proportional to thelength of charged particle trajectories.
We have previously established a correlation between energy measurements and track length of high-energy hadrons and electron showers [2].
This relationship is depicted in Figure 1 as a scatter plot, where different
energetic particles are presented by distinct colors.
The investigation yielded four significant findings.
1. A conspicuous and robust correlation between the two parameters;
energy deposition in scintillation glasses and track length in lead
glasses.
2. The correlation line, represented by a one-dimensional function, exhibits a consistent and unvarying slope across different energies.
3. The intercept of the linear fit line is directory proportional to theenergy of the injected particle, thus indicating excellent linearity of
the calorimeter.
4. The linear correlation pattern is observable across various particle
types, including pions, kaons, protons, neutrons, and electrons.
In Figure 1, we also include the overlay of an electromagnetic (EM)shower events by electrons. The maximum energy observed in hadron
showers corresponds to fully EM shower energy events, including of neutralpions. This region corresponds to the EM shower events of electrons,
which are represented by black dots in the highest energy range of the
figure.
To realize a large homogeneous calorimeter in practice, several challenges need to be addressed, including cost, light absorption, and precise
separation of scintillation light from the relatively weak Cerenkov light.
In this paper, we present an innovative solution that offers a cost-effective,
radiation-tolerant, and straightforward approach to overcome these challenges. Our proposed method involves utilizing a sandwich structure composing two distinct types of materials; a scintillator glass with the ability
to emit scintillation photons, and an ordinary glass specifically chosen for
Cerenkov light measurement. By incorporating these two materials in thecalorimeter design, we can effectively separate the Cerenkov light fromthe scintillation photons with high precision.

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Figure 1: Correlation plot between energy deposition and track length for ahomogeneous glass scintillator calorimeter. The plot showcases the relationshipfor incident positive pions and electrons. The pion data are displayed using
various colors, with red indicating 10GeV, blue representing 5GeV, and green
denoting 3 GeV). The electrons are presented by black dots and corresponded
to three different energies (10GeV, 5GeV, and 3GeV).

The advantages of this approach are manifold. Firstly, it offers an
inexpensive alternative compared to homogeneous calorimeter, making it
more accessible for large-scale calorimeter implementations. Additionally,
the proposed solution demonstrates excellent radiation tolerance, ensuring
the long-term stability and durability of the calorimeter under high-energy
particle interactions.
To validate the effectiveness of our proposed approach, we conducted
extensive simulations to evaluate its performance. The simulation results
provide compelling evidence of the method’s capabilities in separating andaccurately measuring both scintillation light and Cerenkov light within thecalorimeter structure.

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Simulation and results

The simulation conducted for this study assumed a simplified configuration involving a combination of glass-scintillator and lead glass layers.
However, it is important to note that in an actual detector, each layer
would consists of 3cm×3cm×1cm thick tiles. The calorimeter system
would comprise 50 layers, stacked together to form a three-dimensional
structure. This design follows the guidelines of PFA directed calorimeters,such as the one utilized in the International Large Detector (ILD) [3].
To facilitate the readout of both scintillation and Cerenkov light, asilicon photo-sensor on tile technology allows for efficient detection andmeasurement of both types of light within the calorimeter system [4].
The combination of lead glass and scintillation calorimeters, forminga Double readout Sandwich Calorimeter (DSC) (as depicted in Figure 2),3

ensures optimal performance and enables the accurate determination ofenergy deposit.
The DSC configuration, with its innovative readout system, offers several advantages. It enhances the precision and resolution of energy measurements, allowing for finer granularity and improved spatial resolution
within the calorimeter. This is crucial for capturing and analyzing the
intricate details of particle showers and accurately reconstructing theirenergy profiles.

Figure 2: Schematic of the proposed double readout sandwich calorimeter. The
calorimeter structure comprises two distinct layers; lead glass and scintillator
glass. Each layer consists of the tiles, meticulously designed to meet PFA.
To facilitate efficient readout and measurement, each tile is equipped with asilicon photo-sensor. The photo-sensor captures and detects both scintillation
and Cerenkov light emitted by the tile. The electrical signals generated by
the photo-sensor are processed on the a dedicated readout board within thelayer, directly connected to the tile. Subsequently, these processed signals aretransmitted to the external Data Acquisition (DAQ) system for further analysis
and processing.
In the simulation conducted to assess the physics performances of thecalorimeter, we simplified the model by neglecting the effects of silicon
photo-sensors and embedded electronics layers. This simplification allowed us to focus specifically on the calorimeter response. Consequently,
the energy deposition was measured solely in the scintillation glass layers,
while the track length was measured exclusively in the lead glass layers
for positive pions of 10GeV. The correlation between energy deposition
and track length is presented in Figure 3, resembling the correlation plot
observed for the homogeneous calorimeter (Figure 1).
The overall dimensions of the simulated calorimeter system were set
to 2m×2m×2m, while the tile sizes standardized at 3cm×3cm×1cm thickfor both scintillator and Cerenkov layers. For consistency, we employedidentical lead glasses in both the scintillation and Cerenkov layers, ensuring that they had the same components and density, which was measured
to be 6.220g/cm3.
To conduct the simulations, we utilized the GEANT4 10.07 simulation

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framework, employing default parameters. The hadron interaction model
employed is FTFP BERT [5][6], which provides a reliable representationof hadronic interactions within the simulated environment. By adopting
this simulation framework and incorporating these specific parameters, weaimed to accurately assess the performance of the proposed calorimeter
design and evaluate its effectiveness in measuring energy deposition andtrack length for various particles and energy ranges.

Figure 3: A correlation plot of the energy deposit (ED) versus and track length(TL) for 10GeV pions 10,000 events. Notably, a clear correlation is observed.
Additionally, projected plots are included in this view, specifically representing
the energy sum measured in the scintillation glass layers only. Moreover, theoptimized energy resolution of the calorimeter, determined by calculating theshortest distance to the one-dimensional fitting line in the correlation plot, isplotted alongside the correlation plot.
The correlation plot showcases the relationship between energy deposit
and track length, revealing the distinctive behavior of different particles.
Among them, 10 GeV positive pions exhibit a particularly pronounced
correlation pattern. Furthermore, to provide additional insight, projected
plots are included to highlight the energy sum exclusively measured in
the scintillation glass layer. These projections offer a focused view of theenergy deposition characteristics within the calorimeter.
Additionally, the optimized energy resolution of the calorimeter is determined through a meticulous analysis of the correlation plot. By calculating the shortest distance to the one-dimensional fitting line, the optimized energy resolution is obtained. This information is plotted alongside
the correlation plot, providing valuable insights into the performance andcapabilities of the proposed calorimeter design.
The plotted data in Figure 4 provide insights into the response characteristics of the DSC when subjected to 10 GeV positrons. The response of
the scintillation glass layer, indicative of the energy deposited by the particles, is depicted on the vertical axis in MeV units. On the horizontal axis,
the response of the lead glass layers is presented as track length, allowing
for the measurement of the particle’s trajectory within the calorimeter inmillimeter units (mm).
By analyzing the response data in this configuration, it becomes possible to discern the behavior and performance of the DSC for 10 GeV

5Figure 4: Response of DSC for 10 GeV positrons + . The vertical axis represents
the response of scintillation glass layer, measured in MeV units. Meanwhile, thehorizontal axis displays the response of the lead glass layers, represented as track
length in millimeter (mm) units.

positrons. The response characteristics of the scintillation and lead glass
layers provide valuable information regarding the energy deposition andtrack length measurements, respectively, contributing to a comprehensive
understanding of the calorimeter’s capabilities and its suitability for highenergy particle detection. Since the both glass measure the electromagnetic (EM) shower, the sum of these two components remains constant,indicating a linea response characteristic for electrons.
The energy resolution of DSC is determined by projecting the line oflinear fit to the hadronic clusters. This projection distance necessitatesa linear transformation and a normalized factor, denoted as ’c’, derived
from the energy deposition (ED) and track length (TL) measurements.
Specifically, the parameter ’c’ can be obtained
from the fitted straight√line equation ED = a × T L + b as c = 1/ 1 + a2 , where ’a’ and ’b’ represent the linear fitting parameters as usual. By applying this projection
and normalization, the energy resolution can be determined at the incident beam energy. The projected energy distribution provides valuable
insights into the DSC’s energy resolution performance. Table 1 presents acomparison of the energy resolutions achieved by the DSC, the glass scintillator homogeneous calorimeter, and the conventional energy deposition
sum calorimeter of glass scintillator. The specific energy resolution values
for each type of calorimeter are listed, highlighting the performance of the
DSC relative to the other calorimeter configurations.
In this study, we compared the performance of the proposed DSC withthat of a homogeneous calorimeter and a conventional calorimeter.
A homogeneous calorimeter measures the total energy deposit of theglass scintillator and lead glass layers and as well as the sum of the track
lengths of both the scintillator and lead glass layers, followed by onedimensional fitting to create a correlation line and projected to be perpendicular to the line. The energy resolution is determined by projecting

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Positive pion energy (GeV)

Energyresolution (%) for
DSC

2
3
4
5
10
20
30
50
100

5.11
4.99
4.35
3.94
2.46
1.71
1.40
1.21
1.10

Energyresolution (%) for
homogeneous
calorimeter
4.88
4.11
3.59
3.14
2.10
1.63
1.57
1.51
1.65

Energyresolution (%) forenergy deposit
calorimeter
14.18
12.68
12.16
11.58
8.76
6.78
6.12
5.54
5.07

Table 1: Table of the energy resolution of three different glass calorimeters as
a function of incident positive pion energy. (a) glass scintillator and lead glass
sandwich calorimeter (first row), (b) scintillator glass homogeneous calorimeter(second row), and (c) traditional energy measuring scintillation glass calorimeter(third row).

the data perpendicular to this correlation line. On the other hand, DCS
calorimeter measures the energy information from the scintillation glass
layer, and measures the track length from the lead glass layer separately,
and creates a correlation. In contrast, a conventional calorimeter consists of a fully active scintillator glass layer and measures the total energy
deposit within the calorimeter without distinguishing between different
materials or layers.
Figure 5 presents a comparison of the energy resolution performanceof these three types of calorimeters as a function of particle energies.
By evaluating the performance of these calorimeters, we can assess
their effectiveness in accurately measuring and characterizing energy deposition and track length of particles. The DSC calorimeter offers theadvantage of separate measurement and correlations in a straightforwardmanner, allowing for a more detailed analysis of particle interactions
within the calorimeter, especially when the layers are subdivided into
tiles. The DSC calorimeterp demonstrates an impressive energy resolutionof approximately 9%/ E(GeV), which is exceptional for a high-energy
hadron calorimeter. This remarkable energy resolution positions the DSC
calorimeter as a critical component in future calorimeter designs.
One of the key strengths of the DSC calorimeter lies in its finely
segmented three-dimensional structure, allowing for precise localizationand measurement of energy deposits. This segmentation enhances thecalorimeter’s ability to accurately capture and analyze particle interactions.
Additionally, the DSC calorimeter offers excellent timing capabilities
due to its Cerenkov photo-detection mechanism. This timing precision
provides valuable information about the particle’s trajectory and enables

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Figure 5: Eenrgy resolution of hadron calorimeters for high energy positive pios.
Three different types of calorimeters are compared : conventional calorimeter(red triangles), homogeneous calorimeter (green circles) and DSC calorimeterp(blue squares). The blue line represents the energy resolution of 9%/ E(GeV).

advanced event reconstruction techniques.
As a result of these remarkable features, DSC is expected to play a vital role in the development of future calorimeters. Their finely segmented
structure, exceptional energy resolution, and enhanced timing capabilities make them an appealing choice for high-energy physics experiments,
enabling more accurate and detailed measurements of hadron showers.
In the simulations conducted for this study, the effect of photon statistics was not considered. However, it is important to note that the small
size of the tiles in the calorimeter can significantly improve the energy
measurement by ensuring a large number of tiles for the smallest energy
deposit caused by ionizing particles. This abundance of measurements
contributes to a more accurate determination of the energy deposited byparticles.

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Another aspect to consider is the reabsorption and conversion of Cerenkov
light into scintillation light within the glass scintillator. The light absorption properties of the scintillation glass itself offer the potential to minimize the contribution of Cerenkov light to the scintillation light. Typically,
the glass exhibits strong absorption at wavelengths of 400 nm or less, effectively absorbing the majority of Cerenkov light generated within the
scintillation glass. However, experimental validation is required to confirm this assumption. The development of heavy scintillator glasses thatprovide sufficient light yield for minimum ionization particles (MIP) is asignificant challenge for future advancements. It is desirable to explore thepossibility of developing glass scintillators with high density and increased
light output. Quantum dots technology, which has gained attention in recent years, holds promise for achieving these objectives. Urgent efforts
should be directed towards the development and implementation of suchtechnologies. While ensuring the mechanical stability of the calorimeter
structure is crucial, it may be possible to enhance stability by introducing
a mega-tile structure that subdivides a large plated glass. This approach
could potentially improve the overall mechanical integrity of the calorimeter system.
In summary, future research endeavors should focus on addressing theimpact of photon statistics, validating the reduction of Cerenkov light absorption, developing heavy scintillator glasses with high light yield, andexploring innovative technologies such as Quantum dots. Additionally,
exploring structural improvements such as the mega-tile design could enhance the mechanical stability of the calorimeter. These advancements
will contribute to the overall performance and feasibility of the proposed
Double readout Sandwich Calorimeter.

9References[1] Christian W. Fabjan and Fabiola Gianotti, “Calorimetry for particle
physics”, Rev. Mod. Physics, 75 (2003) 1243-1286.
[2] Takeshita, R. Terada and Y. Hasegawa, “A study of the relation between track length and deposited energy in homogeneous calorimeterby GEANT4 simulation at high energy”, 2020 JINST 15 C05015.
[3] J. Repond et al., “Hadronic energy resolution of a combined highgranularity scintillator calorimeter system”, 2018 JINST 13 P12022.
[4] A. Laudrain and on behalf of the CALICE Collaboration, “The CALICE AHCAL: a highly granular SiPM-on-tile hadron calorimeter prototype”, J. Phus. Conf.Ser. 2374 012017.
[5] J. Allison et al., “Geant4 developments and applications”,
IEEE Trans. Nucl. Sci. 53 (2006) 270, SLAC-PUB-11870.
http://geant4.web.cern.ch/geant4.
[6] J. Allison et al., “Recent developments in Geant4”, Nucl. Instrum.
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