Speaker
Description
The Forward Calorimeter (FoCaL) is a planned upgrade of the ALICE experiment at the CERN LHC, designed to measure primarily direct photons, neutral mesons, and jets at forward rapidities. These measurements will probe the gluon distributions in protons and nuclei at very small Bjorken-x, where non-linear QCD effects such as gluon saturation are expected to emerge. The electromagnetic part of FoCaL is a hybrid (HGL & LGL) sampling calorimeter made of tungsten absorber layers interleaved with silicon sensors. Its design relies on large-area silicon pad sensors for energy measurement, which must provide a stable, uniform response and a good signal-to-noise ratio.
We report beam test results for an Indian-made prototype p-type silicon pad-array sensor developed for FoCaL. The prototype was tested with electron and pion beams at energies from 20 GeV to 200 GeV. The pion beams were used to characterise the response to minimum ionising particles (MIPs), including the MIP signal distribution and signal-to-noise performance,cell-to-cell performance variation and etc. The electron beams, combined with tungsten absorbers of varying thickness placed upstream of the sensor, were used to induce electromagnetic showers. This made it possible to study the sensor's response to propagating EM-shower signals and to measure the longitudinal profile of energy deposition as a function of absorber thickness. The results will be compared across beam energies to assess the linearity and performance of the sensor.