Speaker
Description
The CALICE Silicon-Tungsten Electromagnetic Calorimeter (SiW-ECAL) is a
highly-granular imaging calorimeter prototype developed to validate
particle-flow calorimetry techniques for future lepton and hadron collider
experiments, using fine transverse and longitudinal segmentation to resolve
individual showers within dense jets. We present linearity and energy-resolution
studies of the SiW-ECAL prototype using positron beam data recorded during the
2026 CERN test beam campaign across six beam energies
(7.5--74~GeV). Energy response is reconstructed using three complementary
estimators -- hit multiplicity, summed calibrated energy, and tungsten-thickness-weighted
energy -- with Gaussian fits performed on purified event samples. Event
selection is refined using shower-shape variables, including MIP-likeness and the
Moli`ere radius, to suppress electronic noise, particle contamination, and shower
leakage, and the resulting improvement in resolution is quantified explicitly
against the unpurified baseline. The effect of channel-level intercalibration is
assessed by comparing reconstructed energies before and after calibration.
As part of this work, we identify and correct a methodological limitation in the
prior estimate of the transverse beam-spot profile: hits in the first detector
layer have already undergone more than one radiation length of tungsten and
therefore trace early shower development rather than the incident beam itself.
We introduce an alternative estimate based on the reconstructed shower barycentre,
compare it against the layer-0-based method, and use the result to inform a
matching Geant4-based simulation campaign at the same beam position and energies.
Preliminary data-versus-simulation comparisons of linearity and resolution,
including a data/MC ratio, are presented, together with an outlook on forthcoming
track-reconstruction efficiency studies using newly available tracking software.
