T3B — an experiment to measure the time structure of hadronic showers

Abstract

The goal of the T3B experiment is the measurement of the time structure of hadronic showers with nanosecond precision and high spatial resolution together with the CALICE hadron calorimeter prototypes, with a focus on the use of tungsten as absorber medium. The detector consists of a strip of 15 scintillator cells individually read out by silicon photomultipliers (SiPMs) and fast oscilloscopes with a PC-controlled data acquisition system. The data reconstruction uses an iterative subtraction technique which provides a determination of the arrival time of each photon on the light sensor with sub-nanosecond precision. The calibration is based on single photonequivalent dark pulses constantly recorded during data taking, automatically eliminating the temperature dependence of the SiPM gain. In addition, a statistical correction for SiPM afterpulsing is demonstrated. To provide the tools for a comparison of T3B data with GEANT4 simulations, a digitization routine, which accounts for the detector response to energy deposits in the detector, has been implemented.

The time structure of hadronic showers in highly granular calorimeters with tungsten and steel absorbers

“…Unless stated otherwise, the analysis includes all T3B first hits in a time window of −20 ns to 200 ns around the hardware trigger time (t = 0). Each hit is characterized by its time, which is determined with a precision of approximately 1 ns [6], by its energy in units of MIP and by its distance from the beam axis, given by the position of the cell it occurs in. Figure 3 shows the distribution of hits for two out of the three variables, namely time and energy, for muons with steel absorbers as well as hadrons for both absorber materials.…”

“…This limit is largely influenced by the high rate of afterpulsing. Further details of the calibration and reconstruction procedure are given in [6]. A time calibration is performed to determine the relative time offsets between the different data sets due to the use of different trigger systems and other changes in the experimental setup which influence signal run times.…”

“…In the present study, the GEANT4 default saturation parameter for plastic scintillator is used, given by k B = 0.0794 mm/MeV [17]. In addition to the simulation of the interaction of particles in the detector provided by GEANT4, the T3B detector response is simulated by a data-driven digitization procedure [6] which accounts for the time distribution of photon signals originating from instantaneous energy depositions and for effects of photon statistics originating from the overall small numbers of detected photons.…”

Highly granular calorimeters: technologies and results

“…Time of first hit distribution of muon data with steel absorbers and hadron data with steel and tungsten absorbers in the T3B detector [11] with steel and tungsten absorbers in a time range of -10ns to 200ns [12] . and T3B (60 GeV π ± ), normalized to the number of events with at least one hit in the FastRPC and T3B detectors, respectively [13].…”

Recent Developments in Geant4

“…Based on the high precision neutron library, it allows for an improved simulation of the time structure and the lateral profile of hadronic showers in neutron-rich materials [230]. Other improvements include a retuned Fritiof model which will be made available in future GEANT4 versions.…”